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Author Topic: Anybody heard of skeleton molds?  (Read 6536 times)

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Offline krsilber

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Anybody heard of skeleton molds?
« on: March 09, 2008, 07:39:12 PM »
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)
  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!
Kristi


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Offline Ivo

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Re: Anybody heard of skeleton molds?
« Reply #1 on: March 09, 2008, 08:12:23 PM »
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.
Ivo
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Offline krsilber

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Re: Anybody heard of skeleton molds?
« Reply #2 on: March 09, 2008, 09:50:18 PM »
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/th_gravicgrapevasepb-1.jpg)

 
Kristi


"The most beautiful thing we can experience is the mysterious. It is the source of all true art and all science."

- Albert Einstein


Offline aa

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Re: Anybody heard of skeleton molds?
« Reply #3 on: March 09, 2008, 10:22:01 PM »
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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Offline krsilber

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Re: Anybody heard of skeleton molds?
« Reply #4 on: March 10, 2008, 04:53:57 AM »
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.
Kristi


"The most beautiful thing we can experience is the mysterious. It is the source of all true art and all science."

- Albert Einstein

Offline Ivo

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Re: Anybody heard of skeleton molds?
« Reply #5 on: March 10, 2008, 07:33:28 AM »
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.
Ivo
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 New Book: The Almost Forgotten Story of the Blue Glass Sputum Flask

all texts and pictures (c) Ivo Haanstra.

Offline krsilber

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Re: Anybody heard of skeleton molds?
« Reply #6 on: March 10, 2008, 08:35:03 PM »
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!   
Kristi


"The most beautiful thing we can experience is the mysterious. It is the source of all true art and all science."

- Albert Einstein

Offline Frank

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Re: Anybody heard of skeleton molds?
« Reply #7 on: March 10, 2008, 09:27:47 PM »
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Offline krsilber

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Re: Anybody heard of skeleton molds?
« Reply #8 on: March 10, 2008, 10:55:12 PM »
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.
Kristi


"The most beautiful thing we can experience is the mysterious. It is the source of all true art and all science."

- Albert Einstein

Offline Lustrousstone

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Re: Anybody heard of skeleton molds?
« Reply #9 on: March 11, 2008, 07:00:39 AM »
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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