Glass Message Board
Glass Identification - Post here for all ID requests => Glass => Topic started by: krsilber on March 09, 2008, 07:39:12 PM
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I posted this question in another unrelated thread, then decided it belonged in one of its own. A few weeks ago someone posted a vase on the ebay Porcelain, Glass and Pottery board, and included a photo from a book that showed a similar pitcher and part of an explanation about "skeleton" molds (see thread http://forums.ebay.com/db2/thread.jspa?threadID=2000493395&start=40). If you'd rather not look at the thread, here is a thumbnail of the pitcher shown in the book discussing the molds, taken at the Corning Museum of Glass:
(http://i99.photobucket.com/albums/l288/krsilber/th_steubenpitcher-1.jpg) (http://i99.photobucket.com/albums/l288/krsilber/steubenpitcher-1.jpg)
Frustratingly, some of the text about skeleton molds was excluded, and I've been curious about them and how they are constructed ever since. I picture a type of blow mold with multiple panels held together by rings, and holes where the glass was allowed to protrude. Here's a sketchy drawing of what I envision. Is this near accurate?
(http://i99.photobucket.com/albums/l288/krsilber/skeletonmoldmaybe.jpg)
Thanks for any insight or comments!
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I would think your mould would be much more solid, with the accurate size of the windows worked out in the steel, closing fully. I do not think you can have a mould which allows patterning and free blowing at the same time. Now if this is a 3, 4 , 6, or 8 sided mould could be determined by the vertical lines in the end product - but your basic assumption is correct. It seems the variety of dedicated product moulds is infinite.
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Thanks for you comments, Ivo! I'm afraid I'm not totally convinced that it's a regular mold, though, partly because of the bits that are visible in the photo of the text describing the process. I've also seen the pitcher in person, and the window-like areas are thicker than the rest of the glass. Perhaps you could achieve that with a totally enclosed mold, but I envision the parison first centered in the area of the windows and when it is inflated those spots remain thick because they're stuck in the openings, while the bubble gets stretched more in the rest of the mold. That's just conjecture, though, and you may be right. Another example of the same type of thing:
http://i99.photobucket.com/albums/l288/krsilber/steubenhawkesvase.jpg
I do believe that there are molds that only partly enclose a blown object. I had a vase that was a good example of the product of one. The lower half above the foot was clearly molded, but the top had no signs of ever touching a mold.
(http://i99.photobucket.com/albums/l288/krsilber/th_gravicgrapevasedetailpb-1.jpg) (http://i99.photobucket.com/albums/l288/krsilber/gravicgrapevasedetailpb-1.jpg)
(http://i99.photobucket.com/albums/l288/krsilber/th_gravicgrapevasepb-1.jpg) (http://i99.photobucket.com/albums/l288/krsilber/gravicgrapevasepb-1.jpg)
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I've also seen the pitcher in person, and the window-like areas are thicker than the rest of the glass. Perhaps you could achieve that with a totally enclosed mold, but I envision the parison first centered in the area of the windows and when it is inflated those spots remain thick because they're stuck in the openings, while the bubble gets stretched more in the rest of the mold.
Actually, normally the reverse would occur. Where the mould was open the glass would blow out thinner.
Can you post a link to the piece on the Corning site?
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The CMOG site is way slow right now, probably because of the news of the Steuben sale. I'm not sure it's on there, I can't get the photos to display. The photos I posted are ones I took, I guess I didn't mention that. Otherwise they'd be better! The light in there is pretty awful.
"Where the mould was open the glass would blow out thinner. " What if it were cooled at the open spots, while the heat of the mold kept the rest of the glass more ductile? Normally the interior of mold-blown objects mostly follows the exterior pattern. Part of the reason I'm wondering whether the mold had open spots is because of some of the text you can see in the photo in the ebay thread. "...hinged ribs to close like a partially...form of the ribs." It's maddening not to be able to read the whole text. Does anyone here have Gardner's The Glass of Frederick Carder? I tried to get the OP of the ebay thread to post a photo of the whole description, to no avail.
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in an open mould the glass would blow out in a bubble until it bursts like a balloon. As soon as the glass goes through the opening, it will go in every direction and close the mould ; you would not get a smooth lens but a pillow shape. Moreover, I cannot see how you could succesfully retrieve the product, even if the mould falls apart like a barrel.
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I finally found another reference to a skeleton "mechanism," patented by Webb: http://www.glassfairs.co.uk/Articles/burmese.htm near bottom of page. Unfortunately it's just a tiny image with no explanation, and it's hard to say for sure if it's applicable to the vases and pitcher that originally brought this to my attention. As far as I can tell, the type of mold in the patent consists of a bunch of metal plates arranged in a circle with edges toward the center, and it's those edges that shape the object; the rest is open.
"in an open mould the glass would blow out in a bubble until it bursts like a balloon." It seems to me that this would only happen if the glass in the openings remained hot enough to keep expanding. It could be cooled by compressed air to prevent this.
There's also the example of items blown into a metal frame that becomes part of the finished piece.
I should say that I'm partly playing devil's advocate here (bad habit of mine) - I don't have any personal experience glassblowing, so perhaps I should be keeping my trap shut!
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AA is a glassmaker.
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Wow, and I see he does some beautiful work! Love the red Cotswold vase.
I feel like I'm out of my league.
So, I'll turn the question around: how would you get thick areas of glass like that using a mold, while keeping the rest of it fairly thin-walled? Have extra metal in just the right places on the parison?
Does the glass cool and harden when it hits the sides of the mold, or can it stretch and expand?
Sorry I have so many questions about this. I'm just really curious, and it's not the kind of thing that's easy to find in books or online.
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Don't know but this four-part mould piece has lenses twice as thick as the body and nothing to feel on the inside (excuse fuzzy pic!)
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In glass pressing the trick is to completely enclose the glass in the mould so it cannot go anywhere else but in the mould. For this the plungers need to have a shape which can be retracted - hence the design limitations of pressed glass. The pressing takes considerable force. For making hollow vessels, two moulds are used, and parts assembled. The difference between thick and thin parts is due to the specific press mould.
In mould blowing the bubble is blown out in a wet wooden mould which is usually hinged; the contact vapour ensures that the mould does not burn. The bubble is turned inside the mould, the result is a uniform, smooth shape and an even, thin wall.
The alternative is a still mould, which is made of cast iron and is always hinged. The outside pattern is worked in the mould, and the bubble fills the space and takes on the outside decoration. The pattern can be felt on the inside of the finished product. The wall thickness will be uniform.
I am convinced your lens vase is pressed. The mould is heated to prevent contraction marks or striae. The better the temperature matches, the better the product. One of the reasons early pressed glass is decorated all over is the limited temperature control available at the time.
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Illustrating the matter of temperature control.
Here is an excellent example of the impact of having an iron mould that is too cool, in this case the effect has been used to create a randomised pattern. Today it is done to produce glass looking exactly as it was before more sophisticated controls were available but at the time the method was first used it was just the only way.
English: http://www.lamberts.de/ecathedr.htm
Deutsch: http://www.lamberts.de/tk.htm
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Frank, nice effect with the cooler metal! (Metal metal, that is ;)) Isn't glass just a fascinating medium? Whoda thunk it would cause a texture like that?
Ivo, those are great explanations, but most of that I know already about pressed and mold-blown glass. I might add that some "turn molds," your second category, are iron as well, but coated with a baked-on cork or sawdust mixture to hold water for the steam - hence their other name, paste molds. The purpose of the steam is to keep the glass from touching the mold, so it remains nice and smooth. This part about press molds I don't get, though: "For making hollow vessels, two moulds are used, and parts assembled." Do you mean two (or more) parts are used? Why would you use two moulds?
As far as I know, Steuben didn't make any pressed glass. So assuming Corning's ID is correct, this was blown. This is supported by the fact that the lower half of the pitcher is fluted, waisted, and of uniform thickness.
Christine, your piece is pressed, and that's why you can't feel any indentations on the inside.
This type of design, with the thicker medallions, seems pretty uncommon. Given Carder's propensity for innovation and experimentation, I think we have to consider the idea that these were made using uncommon techniques.
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One mould for the inside (plunger) and one for the outside. Both can be patterned.
I cannot think of any method of making the 'medallions' in a blow mould that would defy the laws of physics - so if Corning 'never' pressed glass then you can rule them out. However, you could contact them while they still exist and ask them. I see no reason why an operation that has been as innovative would eschew the the use of pressing to achieve a particular desired effect, at the prices they sell the work for the cost of making a mould for a short run is not prohibitive.
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American cut glass of this time (1905-1912, according to the Corning Museum) and this quality was rarely done on figured, pressed blanks. They were used by some companies in the later ABP, but for a poorer quality product directed to a different market.
The pitcher and the Steuben/Hawkes vase I posted a link to in post 3 both have ribbed/paneled/fluted lower halves that are narrower than their bases. It seems like it would be tough to draw these in after they were removed from a press without affecting the ribbing. I really don't think these were pressed.
I've already admitted I'm not a glassblower, but I don't see why you couldn't have some thick glass coming out openings that when cooled (by compressed air for example) would cease to expand while the rest of the parison inside the mold stayed warm enough to continue stretching and filling the space. Perhaps the mold was thin around the windows, and therefore cooled more quickly than the rest. With a paste mold you wouldn't have the problems of direct contact of the glass with the metal. I'm not saying this is the case - I don't know - but to me there must be an explanation more plausible than that these are pressed.
"...Corning 'never' pressed glass..." Corning certainly did press glass, still does! Steuben didn't.
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Now that the Corning site is back up, can you post a link to a better image?
From memory, these pieces were made at a time when Carder was interested in creating in glass the deep engraved qualities found in historic rock crystal vessels and I believe that your ewer, which from memory is quite an important piece, is probably one of those items. he had access to superb cutters and engravers, and it would not have been beyond their skill to work a very ordinary blank into something like this, lenses included. ie the lenses could have been carved in and polished up. That is not to say that this is how it was done. However, I am sure that Corning will have the answer.
I think it is highly unlikely that skeleton moulds, interesting though they may be, had anything to do with it.
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That answer I will readily accept and agree with. It was my first thought upon seeing the pitcher, before reading in the Gardner book that it was made using a skeleton mold - and from there, my imagination took over. I should have known better than to believe what was written there, since it also says it's probably a Stevens and Williams prototype of a Carder piece.
(I'm still curious about skeleton molds, though.)
The description in the museum for the piece says it's engraved in the rock crystal style (although I'm used to thinking of rock crystal engraving as entirely polished, while this isn't) - your memory serves you correctly!
I still couldn't find a photo of it on the CMOG site. I found one of the Steuben/Hawkes vase in a similar vein, though.
http://www.cmog.org/collection/detail.php?t=objects&type=all&f=&s=steuben+hawkes&record=7
I'm out of town right now, but tomorrow I can post a larger photo of the pitcher, though it's the same photo.
I have 100s of photos I took at CMOG, some of which turned out OK in spite of the dim lighting. Do you (whoever's reading this) think people would like to see a few? Would this be the proper part of the forum to post them?
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Posting images taken by you within a museum may be ok, but you should check first that the museum will permit your personal images to be shown via a public internet message board.
If it's ok, then the best course of action is to set up a separate User Gallery in the GlassGallery (such as "kristi-cmog") and simply post an explanatory message in here with a link to the gallery.
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Perhaps a skeleton mould is simply one that forms ribs, optic or other
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Thanks, Kev! Will do.
Christine, I can't say for sure, but it seems from the two references I have seen for it, it's somewhat different from your normal mold types. I'm getting Gardner's book from the library, so at least I'll finally be able to read the whole paragraph about them that he wrote (FWIW).
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I don't necessarily want to revive this topic, but I did tell Adam that I would post a better image of the pitcher (though it's been several days, and I don't know if he'll see it).
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-9394
detail:
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-9393
Here's also the Hawkes vase with similar round bits (I suspect the Steuben pitcher above was also engraved by Hawkes, but wasn't marked).
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-9408
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-9407
Looking at this one, I'm still a little tiny bit skeptical that the "bosses," as CMOG calls them, were all done by engraving alone. It's hard to tell for sure, but the surrounding glass looks quite a lot thinner, and like it was formed in a mold (blown, not pressed!). The ribbing extends right up to the bosses, and I don't see how you could get the thickness required for engraving them, and have the ribbing molded like that.
But maybe this subject has been beaten to death already...I just wanted to follow through on my promise to post another photo. :)
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Aha! More support for my opinion that these were made by a special mold...
I just got back from the bookstore. While browsing, came across a description and photos of a type of mold that was described as being used in the making of "rock crystal" type objects, and it had little gizmos that looked like they were used to make bulges. There was also an original drawing of a vase that looked like it would have had bosses. I'm distressed, dismayed and distraught, because I can only remember that the gadget started with "dis-"! It was used to shape the parison before it went into the final mold. The book is A History of Glassforming, by Keith Cummings, if anyone happens to have it. I didn't buy it, I'm going to look for a used copy.
Also picked up British Glass 1800-1914 -awesome book! Incidentally, they talk about skeleton molds in there, but they show a different thing than Gardner was talking about, or Webb patented.
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Scanned through some material on moulds and pressing machines without finding any term starting ''dis..."". There are a couple of detailed description of some machines here. Patents tend not to use many "technical" names and these probably came into being when people made and used the machinery. But is could be part of a feeder system, there are several. Or part of one of dozens of different types of machine, let alone individual makes of machine. The patents are not easily digestible but they do give a more thorough description than most books.
http://www.ysartglass.com/Moncrieff/Patent/Patuk320034.htm
http://www.ysartglass.com/Moncrieff/Patent/Patuk320033.htm
and here is a catalogue of machines, with less description but more easily digested:
http://www.ysartglass.com/Moncrieff/MoncrieffMonish.htm
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Thanks for the effort, but those are all machines, and they came into use after these were made (generally 1890-1915, but the pitcher ca. 1910 - I should have mentioned that).
I finally found an image and description of the pitcher in another book I have, Sinclaire and Spillman's Complete Cut and Engraved Glass of Corning. I thought I'd seen it somewhere! "Its raised areas were molded in the blowing rooms; its decoration is stone engraved. The Steuben Glass Works was one of several American companies that made such blanks." And another quote from Spillman's The American Cut Glass Industry: "Hawkes and some other firms advertised extensively that they used only blown blanks". I don't know how late they kept making this claim, as in the 20s and later they did cut/engrave some pressed glass, but that was after the ABP.
Now will you believe that the pitcher and vase weren't pressed?
You can contrast these American examples with somewhat similar English ones, pl. 239 and 240 in Hajdamach. The English ones were cut to shape, and you can see how that was possible on the very thick blanks. The one on the cover in the middle is intriguing because it has that cameo band that's deeper than the surrounding glass; I suspect that one was partly molded into that shape.
Found yet another example in my photos from CMOG!
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Blowing machines output would still be described as blown blanks, fully automatic machines were a bit later on the market. The earliest machines just did the blowing part, the rest of the operation was manual. Feeder machines to the parison to the mould taking another step out of the way. Look for an early text on Glass Technology, say 1910, to get an idea of the state of the art of the time. I mostly used Cousen which is relevant to c1920 and is something of a bible. Copies are not cheap, but worthwhile as it is in good clear language and covers US practise too.
As yet I do not have any other such volumes in the database, my own library is the next to go in, but not quickly as I now have to catch up on all the other activities for my sites. If I find anything would good contemporary discussions on all the different ways of blowing I will let you know. Later texts tend to omit outdated technology.
Some possibles I don't have:
GLASS MANUFACTURE, ROSENHAIN Walter, 1908
Elements of Glass Blowing. Waran, H. P. 1923
Unfortunately most of the best material is in Journals or in German, the former would need to be consulted at Rakow or other technology libraries.
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I was just a week or two ago asking in the Elegant and Depression glass forum I'm a part of whether machine (non-hand powered) presses were adopted by Elegant glassmakers (e.g. Heisey, Cambridge, Fostoria), and evidently they weren't. I've never seen any mention anywhere of mechanization of ABP glass blowing, and I'm positive I would have come across it if it were in use. The industry was proud of its handmade wares, and even the hand-pressed blanks made by some ABP companies after 1900 were only used for glass geared toward a cheaper market, with lower-quality glass and simpler patterns, not museum pieces.
I doubt you will find any information that will convince me the pieces posted in this thread were made on the rod, with human breath.
I am interested in the conversion to mechanization, though. It's all fascinating! Next time I go to Corning I'm going to have to set aside a week just to hang around Rakow, soaking up all the info I can.
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Kristi:
Gardner's discussion on the use of a skeleton mould has nothing to do with the lenses that you are so interested in. He is talking about the process of making vertical indentations or ribs in blown glass. He then uses the lovely blown pitcher, that started this discussion, as an example because of the identations on the lower half of the pitcher not the lenses. This is right in line with Hajdamach's thinking.
To figure out how the lenses were made, a person knowledgable about glass production needs to get their hands on that pitcher and examine it in detail.
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Gardner's description is about the general working of a skeleton mold, and doesn't go into the bosses, but it's the basic idea that's important.
I just got Gardner's book from the library. I sat in the parking lot, read the passage, and thought about it. And I think I figured it out. Whether you all agree or not is another question! I have the distinct advantage of having seen a photo of the type of mold this was made with. The bottom diagram on this page I posted earlier gives a general idea, sort of:
http://www.glassfairs.co.uk/Articles/burmese.htm
(Another somewhat related visual clue I came across was a photo of a vase blown into a metal frame that remained part of the piece. It was point out the large openings in the frame had large bubbles of glass coming out, and the glass exposed by smaller openings was virtually flat. Not surprising, but a nice little demonstration of how glass will tend to expand.)
The reason it's called a skeleton mold is because it's not enclosed. There are simple versions, with a bunch of rods stuck in wood, and these form ribs on the bubble. The one that made the pitcher is more complex. Gardner describes it like the skeleton of an umbrella (handle up). There is a basal plate holding a bunch of pieces of metal upright in a circle, and they are hinged at the bottom, so they fold toward the middle. Some of them form ribs, but there are also some "arms" that have rings on the end (the one I saw a photo of had heart-shaped ones instead of ovals or circles). I believe the latter move independently of the ribs. A bulb-shaped gather just slightly inflated is put in the mold and the ring arms are contracted, "grabbing" and shaping the bosses while the glass is still thick. As the parison is expanded, these move outward, so there is little pressure on the glass to expand inside those areas. The bubble is inflated until full size, the ribs are shaped by the other pieces of metal, and then the mold is opened, and all the hinged pieces unfold, releasing the item.
Does my description make sense? The idea does, but it's worthless to you if I can't communicate it. I might be able to sketch an example.
I'm no glassblower, but I have watched a fair bit of it, and have a reasonable grasp of the behavior of glass. I think this would work, and it ties in with all the bits and pieces of information I've gathered. And most importantly, it fits the glass. All four examples I've posted in this thread show the same characteristics, ones that can't be explained by any other method mentioned.
Any comments? Feel free to tell me I'm dreaming...I'll just have to find more evidence! ;D
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Sid,
Great to see you here! I'm still trying to conceptualise these things. Would that be what they call a dip mo(u)ld to make optic ribbing? Or is it more that at some stage the gather would be blown into a ribbed former?
Kristi: I've just seen your reply, which would imply a rather complicated form of the latter.
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A dip mould is used by glass-blowers to perform basic shaping before blowing is completed, although I suppose there is no reason it could not be used to create a final shape to part of the vase. It is also used to create striping in marvered enamels. It is usually one piece and can be wood or iron. Bronze would be an expensive material but excellent for very fine detail and totally wasted on a dip mould.
The Ysart's at Vasart also used spoked wheels to form wavy edges on the rim.
The main pointer to a piece being mould rather than free-blown is the finish of the base as mould blown would not use a punty, of course if polished flat there would be no evidence left if a punty had ever been used.
The discussion may have lost focus on the lens forming, but is still interesting and useful. Do check out the earlirer discussions on moulds in the Archive forum.
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Hi,
Today I was in London with an ex Whitefriars Master glassblower. I showed him the image of the jug in question and his immediate reply was " cast on bosses ". He agreed with Adam that any glass going through a aperture in a mould would tend to thin.
I have a bowl designed by my Grandfather that uses bosses as a form of decoration and you can see clearly the effect they have.
See image below.
Regards
Patrick.
Ps. This is hand blown and no moulds are used !
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(I'm surprised and pleased that such an esoteric question is still interesting people!)
Patrick, no molds are used? How were the bosses shaped? What are "cast on bosses"? Were they applied? Cool bowl!
I think it's great that this forum is full of people who have personal affiliation with the glass industry.
"Gardner's discussion on the use of a skeleton mould has nothing to do with the lenses that you are so interested in." Sid, Gardner says, "The completed form had a pillared effect, surmounted by a row of convex shapes with a lenslike appearance." Sounds to me like it had something to do with it!
"The discussion may have lost focus on the lens forming" - not true at all!
OK, everybody, can you just keep an open mind for a wee while? Just try to understand this explanation? I'm not simply making up something that will fit my imaginary scenario, I'm drawing together the information that I've read about the glassmakers, these pieces, and the type of mold that at least two authors say is used to make this form of glass. As I understand it, they were uncommon, probably not used much in the last 100 years, and may not have been used much in Britain at all, so I'm not surprised that even glassmakers don't immediately think of them. I believe it's also important to look at all four pieces I've posted with these bosses to get an idea of the form of the glass, rather than going from a single image.
I must not be describing the technique very well, so I'm going to take another stab at it, providing visual aids. Please excuse my drawing! First visual aid (last image below, I bunged up the attachments) is something I mentioned in my last post: a glass object blown into a metal structure that become part of the finished piece. Where there are big holes in the metal, the glass inflates a lot, puffing way out, and where there are little ones it hardly sticks out the holes at all. The more restrictive the space, the less inflation there is. This is based on a piece I saw in A History of Glassforming, and the caption discussed this phenomenon. Makes sense intuitively, but it's important to understand for the rest of the explanation.
An imaginary visual aid: you're making a pizza, but before you stretch the dough out fully you put a cookie (biscuit) cutter on a glob of dough and leave it there. When you stretch the rest of the dough, the glob remains thick in the cookie cutter. Agreed?
Now for the real stuff (basically a repeat of what I said in my last post). The second sketch below is a (lame) drawing of part of a skeleton mold. I've termed the parts that make the ribs, "rib arms" and those that form the bosses, "ring arms." They are hinged at the bottom, and move inwards and outwards, and the basal ring plate locks them in position. The ring arms move independently of the rib arms.
A slightly inflated parison is put in the mold. The ring arms contract, "grabbing" a glob of the thick glass. The parison is inflated with the ring arms unlocked, so they move with the bubble as it expands, and there is little pressure on the glass in the rings to inflate. It is blown until the ribs are formed by the rib arms, then those are unlocked, the whole mold is opened up, and the item has its basic form. Then it's shaped and finished as necessary.
Can you all see now how this might work?
Just one more thing. I'm reposting a detail shot of the bosses on the pitcher, and also another Hawkes vase with bosses that I haven't posted. Notice how much more regular the optics of the bosses are in the second example, with hardly any distortion, and how the bosses don't stand out from the body of the vase. The glass is also quite thick. I believe these bosses were cut, not molded.
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Another possible reason no-one has heard of those moulds (yet) is that they are very complicated and difficult to make and maintain with the temperatures and forces involved. Lots of patents exist for impractical ideas, some of which never got past the drawing stage. I like the suggestion of cast-on lenses, it makes a lot of practical sense.
This type of 'How-did-they-do-that' question can take a long time to resolve. People are still arguing about how the Roman Cage-cups were made. But in the process we are all learning a lot too.
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Hi,
The cast on bosses are made in a similar way to a paperweight ball being dropped on to the button. The bosses on the jug could have had none uniform bosses that were later cut and polished as lenses. My friend said that if he was able to check the internal area of the jug's bosses he would know for sure. The inside of a mold blown item usually follows the external shape , therefore there would be an indent. Can you check this back at Corning ?
Regards Patrick.
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Kristi:
Good work. This discussion is a good example of how this group brings out good outcomes. Your initial concept was completely different than what you have found, through research and diligence, to be the tool that was used to make your pitcher. The glass workers on this board said, correctly, that it wouldn't work as proposed. You dug further and found that the tool was not static but instead was dynamic which addressed the issue of what would have happened in a constrained mould. Without the moving parts, the glass blower would have had a mess on his hands. I could have chosen better words in my posting but stand by them. I have gone back and re-read the Gardner page provided in the initial posting again and still cannot see anything that speaks of the mould making the convex lense shapes. Now that you have a copy of the entire writeup from Gardner, could you please transcribe it for the group so we can close the loop on this discussion? Thanks. By the way, this group has an open mind and loves esoteric - that is why we are still discussing this!
Cathy B.
The skeleton mould that I saw in action in West Virginia was a simple static version with vertical tubes rising in an inverted cone. It was used as a dip mould with the gather quickly inserted, expanded slightly with a small puff of air provided by the blower, and removed before being blown to the final shape in a foot operated paste mould. The sole purpose of the skeleton mould was to provide an optic to the glass object. The blower used a slight turn in the final mould to make the optic a swirl instead of a simple vertical. From what Kristi has found, they clearly could get much more complicated than that with moving parts. I think it was Masterpiece Crystal that we visited. They had a goodly number of these in their mould room in different sizes, diameters of tube and number of tubes.
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Wow, thanks Sid! I was just about to post a reply, part of which was, "Pressed, machine blown, mould blown in a regular mold, cut, cast on...what technique will you guys think of next? Is the skeleton mold explanation really so hard to believe?" So it's really gratifying to hear someone say I found the tool! A believer!
Gardner on skeleton molds: "The repoussé goblets of German silversmiths were the inspiration for a few unusual pieces made at Steuben in skeleton molds. The operation of the skeleton mold utilized a principle similar to that of opening and closing the ribs of an umbrella. The mold was first placed on the floor of the blowing room with the ribs open in a pattern radiating from the mold base. The bulb-shaped gather of molten glass was placed at the center of the mold, and a sliding ring encircling the ribs was pulled slightly upward, causing the hinged ribs to close like a partially folded umbrella. This ring held the ribs in place until the glass gather had been expanded into and through the cagelike form of the ribs. The ring was then lowered, allowing the ribs to fall away from the glass object, which was then finished offhand by adding the applied foot and other elements and fire-polishing the top. The completed form had a pillared effect, surmounted by a row of convex shapes with a lenslike appearance. An engraved decoration was usually added to accent and enhance the molded forms."
My explanation was somewhat different, of course. I don't know if the "ring arms" were also stationary during inflation, but it seems like what I envision would work better. Maybe Gardner didn't know, or didn't want to try to explain the whole thing. I'm going to have to get A History of Glassforming and take another look at the mold they show.
(BTW, the very next paragraph is "Pressed Glass" - they did do some! But they were "relatively few," and they were mostly flower blocks, glass statuettes, and relief decorated panels produced between 1928 and 1932.)
(...and on the facing page are a couple color plates of stunning Steuben diatreta vases! "People are still arguing about how the Roman Cage-cups were made." (Frank) Seems to me there's no question that they were cut!)
Cathy B, where in Australia do you live? I did my post-graduate research on the Atherton Tablelands, lived there on and off for a few years...and loved it!
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I have been following this discussion with an open mind. I can accept that at least some of the items mentioned may well have been made - at least in part - with a 'skeleton mold'.
Unfortunately, although the information provided here, by all contributors, has been good, it neither proves nor disproves, beyond doubt, the use of a 'skeleton mold' for the lens-like sections. Within the quoted text from Gardner, the important section leaves room for doubt (my emphasis in bold):
The ring was then lowered, allowing the ribs to fall away from the glass object, which was then finished offhand by adding the applied foot and other elements ...
That text can be interpreted as meaning that the lens-like parts were also added after the ribbing had been formed and the mold withdrawn from the item.
This discussion is still open until there is definite proof of the means of producing the lens-like parts.
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I agree, the discussion is certainly still open. I didn't mean to imply that just because Sid or any other person can imagine skeleton molds might have been used means they definitely were. I was just glad to see someone agree that it's not completely impossible that this pitcher was mold blown, with the bosses not actually confined to the sides of the mold.
I'd love to hear more discussion! From discussion like this I learn from you and am inspired to learn elsewhere.
Kurious KS
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Hi,
I think that an inspection of the internal area of the lenses will tell us so much. Perhaps a previous comment about the lens being solid is only an optical illusion ?
Regards ,
Patrick.
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(...and on the facing page are a couple color plates of stunning Steuben diatreta vases! "People are still arguing about how the Roman Cage-cups were made." (Frank) Seems to me there's no question that they were cut!)
see here: http://www.glassmessages.com/index.php/topic,1015.msg106925.html#msg106925
Those making cage cups now (with the advantages of today's technology) strongly disagree with the newer theory, it would be interesting to read the complete study but the summary linked in that thread does leave it as an open question and Lierke herself says that more research is still needed.
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I read that thread a few days ago, found it in the archives. I don't know about diatreta, but Lierke's evidence for Roman cameo being molded instead of blown didn't hold much weight with me. I loved this comment for its articulate derision alone: "Lierke's preposterous idea that they are made by squeezing hot glass through a colander-like mould of plaster is absolutely risible, like most of her impractical theories." Excellent word, risible!
I've heard from the guy that has the vase with bosses. He still has it, but not at home. He's going to pick it up and get back to me.
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Cathy B, where in Australia do you live? I did my post-graduate research on the Atherton Tablelands, lived there on and off for a few years...and loved it!
Hi Kristi - I'm in the much maligned Canberra. It's a great place.
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Hi,
I discovered this interesting film showing glass blowing into a frame. The result certainly looks like lenses.
To see the film go to the "Cafe "
Regards Patrick.
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Thanks, Patrick, cool video! I couldn't get it to work from your blogspot, but went to British Pathe and viewed it. The metal frames are the kind of thing I was talking about when I attempted to explain that different-sized open areas would result in different-sized bubbles ("...a glass object blown into a metal structure that become part of the finished piece."). In the objects in the video, though, the glass would be of a fairly similar thickness throughout the piece, or thinner where openings were bigger, as others have pointed out. The big mystery behind the bosses on the Steuben and Hawkes pieces is how they ended up a lot thicker than the rest (which I'm convinced they are).
Haven't heard back from the guy with the vase. After Easter if I haven't heard anything I'll pester him again.
Cathy, I never made it to Canberra. I've heard it's a very nice city, though!
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I see you already got the book... never mind. :spls:
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The big mystery behind the bosses on the Steuben and Hawkes pieces is how they ended up a lot thicker than the rest (which I'm convinced they are).
Hi, I am still with the idea of 'Cast on bosses '.
Regards , Patrick.
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Hi, Or if there are internal indents then " optical illusion "
Patrick.
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Could this be what you are looking for? http://www.toolsforglass.com/store/other_stuff.html
scroll down to Detachable Fin Mold
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Quite like it, I'd say! Thanks, Adam, for posting that. I think in the earlier version that I believe was used on these pieces, the fins were hinged at the bottom. There were also arms that formed the bosses.
I wrote the vase owner again, still haven't heard back though.
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Hi, Looks to me like a DIP mold for doing ribbing or optics................... Only a thought. Patrick
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Yep, like that, though dip molds are usually one piece. So is the type of mold I'm talking about, if by dip mold you mean something that was used to give an initial shape to a parison which was then further worked.
Seems like with cast on bosses you'd be able to see the juncture. There's no evidence that the bosses were cut anywhere (except on one of the Hawkes vases that has decoration engraved on the bosses, first photo). I've noticed that they all seem to have sort of a border, a impression a few mm wide encircling the bosses, which I believe was created by the mold. It's not obvious enough to be a part of the cut pattern.
I keep coming back to the optical properties of the bosses. If the glass is not indented on the inside and the were cut to shape on the outside, you wouldn't see the distortion caused by the non-uniformity of the glass. Compare the ones we've been looking at with the vase in the second photo, which has cut bosses (and I think is Sinclaire, not Hawkes). The ones on the sides that are refracting the image of the cut design show how little distortion there is. The third photo demostrates pretty well, I think, that the bosses are thicker than the rest of the glass.
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Hi, This looks tasty...................
http://www.fieldingsauctioneers.co.uk/lotDetails.asp?lotsID=18545&menuItemOn=3&salesID=56&hasImage=1
Regards Patrick......
Ps. I am probably going to the auction so will report back .
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Oh my, does it ever! How come they don't have auctions like that around here? (Rhetorical question. No glass=no auctions!) I would love to go to one. I hope you make it to this one and report back.
I wonder how they make some of their attributions.
What's the story behind decanters with bent necks like this? Not what I normally think of when I think of clarets.
http://www.fieldingsauctioneers.co.uk/lotDetails.asp?lotsID=18536&menuItemOn=3&salesID=56&hasImage=1
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Hi, I have just had a closer look at the vase I gave the link to......... It looks as if they are only windows not lenses.... Sorry . Patrick. :-[
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They don't stick out very far, but they don't seem flat, either. Their optics and the border seem pretty similar to the American ones I've posted. They all (except for the one with cut bosses) share the sort of distortion expected from non-molded, uncut glass, and look like they have a flattish ring around them. You can only see it a bit on the top of the oval on the auction one, it may have been cut elsewhere.
I've always been interested in the optical effects of different glass treatments, and have been paying special attention to them lately. There's a lot of glass out there that's supposedly cut but actually molded, especially so-called intaglio pieces.
Huh, this one shares some stylistic similarity to the one posted in the ebay thread. The owner of that vase, Bryan, seems to think his and the pitcher at CMOG are both S&W.
BTW Patrick, you never told me how the bosses on your blue bowl ended up so regular although they were cast on. How would you get an edge like that without a mold or cutting?
(Edit: This may have been made using a similar process to the one I believe was used to make the others:
http://www.fieldingsauctioneers.co.uk/lotDetails.asp?lotsID=18537&menuItemOn=3&salesID=56&hasImage=1
It would be interesting to see....and another http://www.fieldingsauctioneers.co.uk/lotDetails.asp?lotsID=18705&menuItemOn=3&salesID=56&hasImage=1)
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Hi Kristi, You asked how bosses would be cast on, check my recent post in the "Cafe" section.
Regards Patrick.
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Thanks, Patrick, for posting that for me. What a great bunch of films on that page, did you put it together? British Pathe is a cool site, too!
I understood how casting's done already; the thing I'm wondering about is how the bosses on your bowl have flat sides. They aren't just round "bumps," they look more like very short cylinders with curved tops.
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Hi,
Here are 3 close up pics. of the bosses. There are small flat areas on them as if they were tooled in some way. I think when heated they would go flatter. In the last pic. I held a pencil outside the bowl and photographed from the inside .
Best wishes Patrick.
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Thanks for the photos, Patrick! That clarifies things - it must have been an illusion (or delusion) what I saw before. They look different to me now. Sorry about that.
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Hi Kristi,
I went to the Auction , but I had to leave the house at 05.45 and got back home at about 21.00 .......... A very long day ! I am off to Ali Pally at 06.30 for trade entry at 07.00 .
I took some pics at Fieldings and will give you feedback tomorrow afternoon. I am off to bed now . Patrick.
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Ach, what a tease! I'm interested to see how it went and what you found.
I've ordered the book History of Glassforming and it should arrive any day. That's the one I saw the funky mold in. Alas, I guess I can't show a photo of the page on the board here, but maybe I can trace it.
(What's Ali Pally?!)
...that made me go check my mail, and it came!
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Here we have it...Cummings calls it a distorting mould. "A distorting mould operated by an outside ring which is pushed up and down to open and close the brass arms. Unlike bolivers that are designed to shape the rim area, this type of device was used to partially shape the original bubble by distorting its surface into undulations that were reminiscent of rock crystal carvings." There's also an original glassmaker's drawing of a decanter with bosses shown as an example of the type of thing it was used for.
Sorry if the tracing looks sloppy. It's from a 2" image. The mould is pictured here open.
GREAT book, by the way!
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Hi,
Back from the Fair and had a good morning buying four nice Whitefriars pieces.
As I said yesterday was a very long day and I bought nothing , but did bid for a short while on Lot 327 . Not 100% sure but I think the hammer fell at 135.00 , it was stunningly beautiful but I don't collect cut glass . The buyer of this piece went on to acquire most, if not all of the ' Rock Crystal '. My friend was the under bidder on 3 of the lots he won and we suspect he would have bought them at any price !
Lot 165 was also stunning and in great condition. The 'optic' areas were as I suspected only windows being formed by clever cutting of the main body. I have attached an image that I think shows them clearly.
Finally ' Aly Pally ' is a slang expression for Alexandra Palace ............. http://www.alexandrapalace.com/
For many years there was a monthly antiques fair held that was great for buying glass with many more stalls than todays fair. For the last year there has been one and this was a first time in a new series.
All best wishes,
Patrick.
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I agree, in this case it looks like the ovals may be simply areas that weren't cut. But that doesn't mean they're all like that, of course. Thanks for the photos! Makes me so envious; I would have loved to see glass like that in person.
Boy, I'd like to ask a few questions of the buyer of the rock crystal pieces!
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I was browsing Sinclaire and Spillman's The Complete Cut and Engraved Glass of Corning just now. There's a photo of The Pitcher from the OP on a page I've referred to many times, but only now has it gotten through to me what the caption says: "Cut and stone-engraved Steuben Glass Works ewer, ca. 1910, used a molded blank that imitated the cut medallions of costlier rock-crystal designs."
I also found out that Paul Gardner, the author who said the pitcher was made using a skeleton mold, was Frederick Carder's assistant for 10 years. So it seems like he'd be in a pretty good position to know how it was made.
The other day I ran across a tracing I made of the mold pictured in Cummings's History of Glassforming - same mold as the other tracing I posted, but this time in a closed position. I figure I went to the work of tracing it, may as well post it for posterity.
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Good detective work.
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Hello:
Have a look at this webpage. There are many different devices for shaping hot glass including the examples traced by Kristi. They can be seen in figures 21 and 22. Very interesting!
http://aurora.sunderland.ac.uk/gateway_to_glass/htmlsite/h_journal_refereed_19centuryglass.htm (http://aurora.sunderland.ac.uk/gateway_to_glass/htmlsite/h_journal_refereed_19centuryglass.htm)
Have a good look around the rest of the site as well.
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Excellent site! Thanks, Sid. Keith Cummings is the author of the book I traced those from...all that work, and it was on the internet all the time!
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Siemens patented a skeleton mould for moulding bottles and it states, either the article or the mould is rotated during moulding. It does not state the purpose of a mould that has air holes, presumably lower manufacture costs and faster cooling. It states skeleton moulds may be built up of bars.
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When was this? Do you have a copy of the patent, or a link? I'd like to see it. My guess is it's not related to the moulds discussed here previously.
The object/mould would be rotated presumably to avoid the texture given the surface of glass by metal moulds, just as an object is rotated in a turn/paste mould. If the interior of the mould doesn't have a water-retaining surface, maybe the holes inject a bit of air to keep the glass away from the metal? Or they're simply for cooling the mold, as molds used continuously tend to get too hot. I read somewhere the other day about molds that had air circulating through them to keep them cool.
I wonder what it means that they were built up of bars.
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It will be in the next batch of patents I upload I study, so c1878, but nothing more then I said above, other then a picture (I think)
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I think you've finally got it right, multiple fingers with oval openings on the top of them. They are held together with a metal starp that goes around them and keeps them in position. After the parisom is expanded, the fingers are allowed to fall away from the glass. The center of the parisom can initially be made a lot thicker than the other parts of the piece through bubble control and cooling and marvering techniques before it is ever put in the mold, resulting in the center "lenses" being much thicker than other portions of the pitcher.There are multitude of other techniques that could have been employed to get this same result. i.e. picking up oval lenses on the hot parison before the piece was ever put in the mold and blown out. You can cast these in a row with space between them and roll the parison over them ans pick them up, then blow the piece into a "skeleton"/finger mold that would give you the sides, or do the pickup after the piece was initially blown. or the lenses could have been inserted into depressions in the skeleton mold and kept hot till the parison was inflated and picked up the lenses. Final finishing with hand torches and glaziers could have fire polished these areas then.
Or it could have been blown into a thin metal form with the glass coming thru it and then the metal was etched away from the glass after the piece came out of the annealer. I used to work with a company that did a lot of the blowing into metal frames in the 60's when the "Spanish" and "Mediterranean" styles were popular in the US. The glass could most often be easily cut away from the metal when it cooled.
Just a few more ideas to ponder.
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The object/mould would be rotated presumably to avoid the texture given the surface of glass by metal moulds, just as an object is rotated in a turn/paste mould. If the interior of the mould doesn't have a water-retaining surface, maybe the holes inject a bit of air to keep the glass away from the metal? Or they're simply for cooling the mold, as molds used continuously tend to get too hot. I read somewhere the other day about molds that had air circulating through them to keep them cool.
I wonder what it means that they were built up of bars.
There is another example in the Study patents that was intended to provide standard shaping for wineglass 1873/676
(http://www.glass-study.com/studypic/PatentsUK/UKPat_1873_00676a.jpg)
The bars of the rubber are made of graphite, carbon, &c. and may be straight, spiral, &c. in shape provided that in revolving they describe the contour of the vessel to be formed.
Although this was not specifically named a skeleton mould it does show one of the uses. In this case though the forming bars are fixed.
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Hi,
Brilliant to see this diagram................
By the diameter of the shaft and the size of the flywheel it must have rotated at a good speed !
Patrick :)
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The idea of the flywheel was to to wind the cord again, so each use it would have rotated in the opposite direction. Of course a patent does not mean it was ever used.
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The idea of the flywheel was to to wind the cord again, so each use it would have rotated in the opposite direction. Of course a patent does not mean it was ever used.
Are you sure? I would have thought it was to create a constant speed of rotation.
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Yes, part of the description
The shaft D is then caused to rotate by sharply pulling a cord or strap K coiled upon it. A flywheel H mounted on the shaft serves, by its impetus, to re-wind the cord K
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Ok, fair enough, but it is just an ancillary purpose of the flywheel to re-wind the cord. The cord is really there to rotate the flywheel!! The reason for the flywheel, surely is to ensure a constant speed of rotation.
Otherwise, you could spin the flywheel by hand and a cord would not be necessary. Indeed, I wonder how long the cord method lasted before they realised you could get just as good a result by spinning the flywheel by hand! :) Probably less hassle as well.
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Hi,
I think the key to this is the " sharply pulling " This would get the flywheel going a good speed. As Adam says the cord would rewind itself immediatly you let go at the end of the pull !!!!!!
Regards, Patrick.
Ps. I sold mt Meccano sets long ago otherwise we could have tried one at Adams.
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Thanks for posting the diagram, Frank!
After reading the patent, it seems to me the flywheel and cord were meant to rotate the mold smoothly and rewind it. Pulling a cord once is a quicker, easier, one-step way to rotate the mold than turning it by hand - a single person could set it in motion then put the bubble into the mold. Or does the bubble have to go in first? I'm a little confused about the bars, and the mold itself. Do the bars slide over the glass, forming it that way, or do they grip it, so that the centrifugal motion of the machine expands the glass out between the bars?
Of course a patent does not mean it was ever used.
Yes, I've been thinking about that lately. There must be a lot of patents out there that were never used for commercial production.
One thing I've been wondering about is patents for glass formulas. It seems like many of them are sort of wishy-washy, saying the formula contains (four particular ingredients) plus additional ones, at the maker's discretion. This one, for example: http://www.google.com/patents?id=jpNpAAAAEBAJ&printsec=abstract&zoom=4&dq=1629648
It says, "My invention is applicable to any sand and soda ash mixture with or without other ingredients and the addtion of litharge, borax and manganese is optional." Two specific formulas are give at the end - is the patent, then, just for those two formulas?
I think you've finally got it right, multiple fingers with oval openings on the top of them.
Tom, thanks for checking in ... it's always nice having another glassblower's ideas, and further confirmation that the distorting/skeleton mold Cummings describes could have been used on the pitcher in the OP. No doubt the bosses could have been made using other means, but my original question about skeleton molds seems to have been answered. :) :) :) "Final finishing with hand torches and glaziers could have fire polished these areas then." Any idea when the use of hand torches began? What's a glazier?
BTW, do you all remember the vase that apparently has the same design as the pitcher? I FINALLY heard from the owner a week ago that it is smooth on the inside, with no depressions behind the bosses. Perhaps that means it wasn't made using the same type of mold, or maybe with the thicker glass there that Tom was talking about they just don't show up because that part wasn't really blown into shape, as the thinner glass was.
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After reading the patent, it seems to me the flywheel and cord were meant to rotate the mold smoothly and rewind it.
Agreed
Pulling a cord once is a quicker, easier, one-step way to rotate the mold than turning it by hand - a single person could set it in motion then put the bubble into the mold.
That may have been the intention. However, I don't agree that pulling the cord would necessarily give a smoother rotation. That is just an opinion based on conjecture. It may be right but I think that it is important, when trying to analyse things "backwards' to consider all the options. That is, presumably, the essence of research.
There are not that many parallels between glass and ceramics but here http://www.youtube.com/watch?v=CwFtg8mBW3s you can see one of the most accomplished potters ever, Shoji Hamada, working on a wheel that is hand rotated on a weighted flywheel - you will see the motion of the rotation which was done by using a stick that was placed in a groove on the wheel.
This illustrates that you can achieve a very satisfactory constant level of rotation by hand-turning a flywheel.
I am not sure whether the cord-pulling method would be practical because you I think you would have to let go of the cord as soon as you had pulled it, and then there could be a risk that it would not rewind evenly. If you held on to it, you would risk losing your fingers. There would obviously been a boy (assistant) to pull it, but they could just as easily spin the flywheel. It might be easier to get sufficient torque by doing this then by pulling a cord. We used to have a electric motor on a flat bed grinder that required so much torque to start that it is best to hand spin it a couple of times and then switch off the motor, rather than risk it cutting out at the breaker.
It would be very interesting to learn if anyone has actually seen one of these in action. For all we know it was actually an idea that never made it off the drawing board. I am not actually sure what benefits would be achieved by using it as I think there are probably simpler ways of achieving the same result.
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Pull the cord to get it turning, hold on to it until it is rewound then let go, solves simply that problem - visions of a boy wrapped around a spininng shaft :o
In time the patents in the study can be annotated as to their use, I have some data to start that process but at the moment concentrating on the digitising. It is also clear that patents were being created just to try and profit from a process, as is common today too and it is up to the examiners to prevent too much of that getting through. Patents can also be challenged later. Originally patents were issued by the crown or similar in a fairly arbitrary way based on personal relationships... a study of 17th Century glass patents is fascinating as they were granted and cancelled at a whim - often in return for some form of substantial incentive.
No doubt more will appear in the skeleton mould story and there are still unanswered questions on the subject.
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Try this. Assuming you have a bicycle, turn it upside down on the floor. Attach a piece of cord to the pedals. Pull it. See what happens. Now try spinning the wheel by hand. See what happens. Let us know which works better. ;D
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However, I don't agree that pulling the cord would necessarily give a smoother rotation. That is just an opinion based on conjecture. It may be right but I think that it is important, when trying to analyse things "backwards' to consider all the options.
Certainly, one must consider the options. Whether a cord or some other manipulation produces a more constant motion isn't entirely conjecture, though, but also a matter of experience. Personally, I would find using a cord easier.
Once the cord was pulled and released, the only thing preventing a constant rotation would be friction, which you'd expect to be constant (unlike that when throwing a pot). Using a cord would mean a greater speed could be achieved, just as you pull a cord on a gyroscope to start it turning, or on a lawnmower. It seems to me it would be easier to keep the tension on the cord pretty steady when you're setting a flywheel in motion that way than to turn one by hand, when it would be natural to use more force at some point in its rotation (as one is pushing down, for instance).
I wondered about what happens to the cord once it was released, too. Presumably the turning of the shaft, if fast enough, would hold it in place.
I didn't watch the whole Hamada video, but I didn't see any fly wheel there, only the one the pottery is made on. Hamada's wheel slows quickly as soon as he stops turning it, suggesting there isn't one, and a lot of time is spent just getting the thing going. These days (in America, anyway) person-powered potters' wheels are connected to a flywheel that's kicked. In either case, one benefit is that the speed can be controlled easily, but you have to keep working at it to make it go the speed you want. In the case of the patent, you put the bubble in the mold, pull the cord, and you're done. Theoretically, anyway!
(written while I was writing this post:)
Try this. Assuming you have a bicycle, turn it upside down on the floor. Attach a piece of cord to the pedals. Pull it. See what happens. Now try spinning the wheel by hand. See what happens. Let us know which works better. ;D
Well that wouldn't work! Attach it to the pedals? You'd have to attach it to the sprocket, and wind it up, pull...then see which works better!
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One benefit of the cord is that it would give a more consistent speed than pushing the flywheel. Theother use of the flywheel would be to help overcome the friction drag.
The cup was made of graphite or other materials - what would be the impact of blowing the bubble to hard... little bits of hot glass sliced off and flung away :huh:
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Gear or direct drive?
On a lawnmower or an outboard motor, a cord works because there is a flywheel to which the cord is attached. The purpose of the flywheel in those examples is to make it easier to pull. The flywheel in those examples works as a gear, which means that not too much effort is needed to start the motor. Which is why you perceive it to be easier to pull a cord.
The whole point is that the diagram shows a cord attached to the drive shaft and as Patrick pointed out originally, relatively the flywheel looks rather heavy. It doesn't make sense to use a cord to start it. It will require much more strength than a lawnmower. Do you have a car, or a bike? Do they have gears or are they direct drive?
In the Hamada example, there is a weighted flywheel underneath the working surface. His wheel was a pre-cursor to the kick start wheels that you refer to. He managed to work out that by pushing the edge of the wheel, it required less torque or strength to turn the wheel than to put crank it from a central drive. This is also a form of gearing. Imagine if he had a hole near the centre of the wheel to put his stick into. Which would have been easier?
You are quite right, attaching a string to the pedal would not work. Well spotted! As you say, you would need to attach the cord to the sprocket, which, again is a gear!! Maybe, what you should do is to attach a piece of steel to the axle of the bicycle and then wrap the cord around that. See if you get a better result than spinning the wheel from the edge.
I am not really an expert in this, but so far as I know, direct drive requires more effort than gears. But I am not an engineer, so I am not going to add much more. Instead, I am hoping that there is an engineer out there who will be able to confirm that it would require less effort and torque to spin the fly-wheel from the edge, rather than pull the cord.
However, I would be equally happy if an engineer can show that that pulling a direct drive cord requires less force. Smiley
I would also be very interested for that engineer to provide an explanation that shows that a using a cord would give a more constant speed than spinning the flywheel, because my very basic memory of studying this stuff about 35 years ago is that the fluctuation of the speed will be primarily related to the weight of the flywheel and any variation to the speed will be related to that as soon as the force is removed. In other words, when you stop pulling the cord, or spinning the flywheel, the deceleration will follow a constant curve.
:hb1: ;D
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;)
This is probably getting too technical for some people, so here is a simpler explanation - you can dilute almost everything down to a culinary example:
Take two egg whites and put each in a separate mixing bowl, each bowl being the same size.
Using a hand whisk or fork, beat the eggs. In the first bowl rotate your whisk in the centre of the bowl on one spot, all the time. In the second bowl, rotate your whisk around the outside of the bowl all the time. Time how long it takes to get the egg whites to meringue consistency. Which is faster? Which is more tiring and uses more effort?
You don't actually have to try it, if you already know the answer!! ;D
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Yes, part of the description The shaft D is then caused to rotate by sharply pulling a cord or strap K coiled upon it. A flywheel H mounted on the shaft serves, by its impetus, to re-wind the cord K
Hi,
As I said before I think the answer lies in " sharply pulling " as in a toy Gyroscope ( Kristi ) . The ENERGY used in the pulling is STORED in the flywheel .
For the bars of graphite to work they must be rotated at a good speed, a slow speed would be no good.
The neatly wound cord in the diagram is just to show the principle, in reality the cord when let go would go more into a ball but still work when it was re-pulled. As I said if I had my Meccano set that had a cast flywheel it would be so easy to demonstrate.
Best wishes, Patrick.
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I have only just seen all this discussion on flywheels and cords, and thought I'd suggest that there is an important point to consider (which has, in fact, already been hinted at but seems to have been forgotten in the discussion of the engineering principles).
I see nothing in the patent diagram or its descriptions to say that the cord is permanently attached to the shaft. I feel sure that the idea is for the cord to be merely wound around it and that it comes free at the end of its pull. The part of the description that states, "A flywheel H mounted on the shaft serves, by its impetus, to re-wind the cord K" simply means to me that when each operation of shaping is done, the flywheel / shaft is braked by some means and the cord is then reapplied to the shaft and the flywheel slowly turned by hand to rewind the cord.
If there is no clutch mechanism (which appears to be case from the diagram) then having the cord attached to the shaft would be highly dangerous, possibly resulting, as Frank suggested, in a boy assistant being wrapped around the shaft (or at least having his fingers broken or ripped off).
Personally I don't have a bicycle and neither do I have a whisk so I can't try the suggested experiments.
However, I do know that a rotating shaft in machinery can have enough energy to quickly wrap long hair around it and rip a whole patch out the human head leaving a 2 inch diameter area of damge - as proven by my brother in the days when his hair was as long as Frank's was in 2005 :o :o :o
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it is smooth on the inside, with no depressions behind the bosses. Perhaps that means it wasn't made using the same type of mold,
So all round the Wrekin, to arrive at the point of departure. This topic has shown an impotent lack of progress, the height of archeological necromancy, that is akin to fortune -telling, and now we know less about so-called skeleton moulds, due to a lack of consideration for the opinions of glass-makers.
Yes I know what the patent says, but all too often, there are flaws which cannot be resolved. After all, it took others to find the real benefits of a patent taken out by the Reverend Stirling, regarding endothermic engines, a mere two hundred years, before a tangible use for his patent was found.
("What I know about glass I can write on the back of a postage stamp ( and imho, that is the way it should stay")) ;D ;D
Bah... humbug....
Regards,
Marcus
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So all round the Wrekin, to arrive at the point of departure. This topic has shown an impotent lack of progress, the height of archeological necromancy, that is akin to fortune -telling, and now we know less about so-called skeleton moulds, due to a lack of consideration for the opinions of glass-makers.
Archeological necromancy? Akin to fortune-telling? How so?
How do you figure we know less about skeleton molds, and who has shown a lack of consideration for the opinions of glass-makers?
Even though this is off-topic, I just gotta respond... ;D
Gear or direct drive?
On a lawnmower or an outboard motor, a cord works because there is a flywheel to which the cord is attached. The purpose of the flywheel in those examples is to make it easier to pull. The purpose of a flywheel is not to make it easier to pull; that wouldn't make sense, since flywheels are heavy and resist movement. The are used to store kinetic energy, as Patrick pointed out. It may still be true that they function as gears as well. The flywheel in those examples works as a gear, which means that not too much effort is needed to start the motor. Which is why you perceive it to be easier to pull a cord.
The whole point is that the diagram shows a cord attached to the drive shaft and as Patrick pointed out originally, relatively the flywheel looks rather heavy. It doesn't make sense to use a cord to start it. It made sense to the filer of the patent! It will require much more strength than a lawnmower. Now this is conjecture! Do you have a car, or a bike? Do they have gears or are they direct drive?
In the Hamada example, there is a weighted flywheel underneath the working surface. Why? If his wheel is heavy enough, it wouldn't need a flywheel. I don't get that. His wheel was a pre-cursor to the kick start wheels that you refer to. He managed to work out that by pushing the edge of the wheel, it required less torque or strength to turn the wheel than to put crank it from a central drive. This is also a form of gearing. No it's not. Imagine if he had a hole near the centre of the wheel to put his stick into. Which would have been easier?
You are quite right, attaching a string to the pedal would not work. Well spotted! As you say, you would need to attach the cord to the sprocket, which, again is a gear!! Maybe, what you should do is to attach a piece of steel to the axle of the bicycle and then wrap the cord around that. See if you get a better result than spinning the wheel from the edge. Betcha I could make it spin faster with a cord around the axle! ;D
I am not really an expert in this, but so far as I know, direct drive requires more effort than gears. Why raise the issue of gears? There are no gears in this picture. But I am not an engineer, so I am not going to add much more. Instead, I am hoping that there is an engineer out there who will be able to confirm that it would require less effort and torque to spin the fly-wheel from the edge, rather than pull the cord. Yes, agreed, but how do you get it to go fast?
However, I would be equally happy if an engineer can show that that pulling a direct drive cord requires less force. Smiley I don't think anyone is arguing that. It would take exactly the same force (or rather work - ergs - to use the proper physics term) to spin the flywheel at a given speed no matter how you do it. Well, unless you weren't spinning it constantly, in which case friction would tend to slow it down each time you stopped, so you'd have to regain that ground.
I would also be very interested for that engineer to provide an explanation that shows that a using a cord would give a more constant speed than spinning the flywheel, because my very basic memory of studying this stuff about 35 years ago is that the fluctuation of the speed will be primarily related to the weight of the flywheel and any variation to the speed will be related to that as soon as the force is removed. True. The heavier the wheel, the greater the inertia. The change in speed will also be related to the friction, which in turn may be dependent on the weight of the flywheel. In other words, when you stop pulling the cord, or spinning the flywheel, the deceleration will follow a constant curve. Exactly!
:hb1: ;D
;D ;D ;D
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http://www.youtube.com/watch?v=7eCsUQAjcI0
Please explain why the crank handle shown is this funny shape rather than being straight. :)
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Hi Adam,
I hope you see me as a good friend of yours but all this talk of egg wisks and now crank handles has me baffled.
Are you saying his original idea that may or may not have been made, would NOT WORK ??????
Regards Patrick.
Ps. No crank here only works by a cord going round shaft and given a good pull........
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I'll call you
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http://www.youtube.com/watch?v=7eCsUQAjcI0
Please explain why the crank handle shown is this funny shape rather than being straight. :)
Sigh. You know why - you can get greater torque with a greater turning radius. I don't question that. But it seems to me speed is the issue here - how to get the thing going fast enough to work. If the axle the cord is wrapped around has a circumference of 5 cm and the flywheel has one of 50 cm, is it faster to pull a cord 5 cm or move your hand in a 50 cm circle? At the beginning you could always start the flywheel with your hand to overcome some of the initial inertia, making it easier to start pulling the cord. Once it gets going faster, can you even move your hand in a 50 cm circle in, say, the space of half a second or a quarter second?
Why do you think mowers and outboards have a cord, rather than a crank? They need the speed to turn the engine over fast enough that it will fire in rapid enough succession to keep going of its own accord. Well, I think so, anyway...I'm certainly no motorhead, and if that's wrong, hopefully someone will correct me.
Just so we all know, this is a friendly discussion, right? and not a heated argument. I enjoy friendly, respectful debates as long as no one takes things the wrong way and gets offended. It's good brain exercise. :)
:) :) :)
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But it seems to me speed is the issue here - how to get the thing going fast enough to work.
Why do you think it needs to go fast?
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Good question! Partly it's because that's the way it looks like it was designed - how's that for circular reasoning? ;D ::) But considering the fact that the patent talks about having different shapes of bars in the mold part, I'm assuming that it works by spinning quickly enough that centrifugal force will expand the bubble around the bars. The other possibility is that the bars slide over the bubble to shape it, but I don't know why you'd put something like spiral bars into the mold then.
It's also presumably supposed to be a time-saving device, so you'd want it to be quick.
The whole gadget seems sort of a waste of effort. Why not just blow it in a dip mold for the same effect? Somehow I doubt it was used in a production capacity. I bet at that time there were lots of people making up new "time-saving" gizmos and whatzits.
Too bad what we're seeing is a patent abridgement, rather than the whole description.
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Glad to see you've worked it out. :)
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What? Just like that? Now I feel kind of bad. I hope you aren't being sarcastic.
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Hi Kristi,
Adam, being sarcastic? Not at all.
Few of us are actively involved in glass-making. Adam is, and when he has reservations, which are based on many years of first-hand experience. maybe he has good reason.
For the rest of us mere mortals, all the theorising could be merely an exercise in intellectual masturbation.
Regards,
M
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after looking at the diagram of that patent further, it was just a simple way to get the mold to move instead of the pipe and glass to turn. It would be the smae as making a machine that would make the wood block turn instead of the glass. I would think it would have been difficult to use and would have worked better with hand crank or a gear driven foot pedal. What year was this patent from? The splines that turned would of had to be very close together to not catch the hot glass as it was turning. It appears like a device designed for use by a glassblower but the designer was more of an "engineer". The angle of the mechanism doesn't seem to be conducive to working conditions very well. I've seen some machines that were a lot stranger than these. I was in one shop in the Czech Republic that had a whole wall of different hand tools that had about 1" of dust on them. I asked what they were and they replied, " they're all the stuff we tried that didn't work very well, but we spent so much time making them we couldn't throw them away."
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Marcus, I get the feeling that you think I'm being disrepectful of Adam, or undervaluing his experience and knowledge. The way I see much of our discussion, it had little to do with glassmaking per se, and more to do with the physics of the apparatus...we were trying to figure this thing out. I think all of us thought the pull cord a little odd, and I was trying to make sense of it - at least theoretically; I'm not sure it would work so hot in practice.
I think it's fabulous being able to talk to Adam! I have very much enjoyed my discussions with him and other glassblowers, and I really value that about this forum. Call it intellectual masturbation if you want (sounds good to me!), I learn so much by bouncing ideas off Adam and everybody else. I expect to be told I'm wrong sometimes, and I want to be told when some crazy hypothesis I have is totally impractical.
Hey hey, I just noticed this last line in the patent: "Motion may be given to the rubber by any suitable means." (Rubber meaning mould)
Ach, just read Tom's reply. Then reread the patent, and he's right, the bubble stays put. "The bars of the rubber are made of graphite, carbon, &c. and may be straight, spiral, &c. in shape provided that in revolving they describe the contour of the vessel to be formed." There goes the centrifugal motion notion.
The splines that turned would of had to be very close together to not catch the hot glass as it was turning.
Could this be a reason it needed to turn fast?
The patent is from 1873.
" they're all the stuff we tried that didn't work very well, but we spent so much time making them we couldn't throw them away."
;D ;D
Yup, this machine is for the birds!
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Might as well quote the entire abstract:
676. Richardson, J. T. H. Feb. 22.
Blowing; moulding. — Relates to the manufacture of tumblers, goblets, and other glass articles. The glass is blown on a tube J which is then placed on guides I on the frame G, and moved slowly downwards to bring the bubble into a "rubber," formed with a base A fixed to a shaft D, and with fixed or movable bars B united by a rim C. The shaft D is then caused to rotate by sharply pulling a cord or strap K coiled upon it. A flywheel H mounted on the shaft serves, by its impetus, to re-wind the cord K. The bars of the rubber are made of graphite, carbon, &c. and may be straight, spiral, &c. in shape provided that in revolving they describe the contour of the vessel to be formed. The shaft may be horizontal or inclined and the apparatus is mounted on wheels to facilitate removal. Motion may be given to the rubber by any suitable means.
Which is patent-speak to cover variations of the theme.