Author Topic: Question re: Cane in a Strathearn P15 Closepack  (Read 917 times)

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Offline mmarc77

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Question re: Cane in a Strathearn P15 Closepack
« on: April 25, 2012, 05:02:41 AM »
Is there any significance as to why a specific cane in a P15 closepack is always encircled with air bubbles? i.e the lime green with black center and red dot. There is an example in Richard More's Strathearn pictures section P15 Carpet Millefiori Closepack Medium to small. The last weight pictured on page two shows two of the same green cane that always appears to have bubbles around it. (I would copy the image but I'm not sure that's allowed) Are the bubbles just part of the cane?

Thanks for any help!!!


Offline Wuff

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Re: Question re: P15 Closepack
« Reply #1 on: April 25, 2012, 08:57:26 AM »
Welcome to the board !
Whilst I cannot answer your question, may I give a couple of hints?

It would be good to mention Strathearn already in the thread title.

Copying images (without copyright holder's permission) is not looked at favourably here - but a link is fine.

Unfortunately I cannot identify the weight you are talking about: the number of weights shown on a "page" depends on the size/resolution of your viewing window - and there is no cane fitting your description on the last weight on "my" page 2.
A link would be easiest for the reader - but otherwise quote the image number (rather than page number), which (I guess) will be unique.

Have fun with the board - Wolf
Wolf Seelentag, St.Gallen
Interested in any aspect of Scottish glass? Have a look at Scotland's Glass.


Offline Wuff

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Re: Question re: P15 Closepack
« Reply #2 on: April 25, 2012, 09:13:56 AM »
Scrolling through P15 I came across image 36 - not the colouring you give, but does this show the effect? In this case I assume the bubbles are actually in the cane - whether on purpose or not, is a different question.
Wolf Seelentag, St.Gallen
Interested in any aspect of Scottish glass? Have a look at Scotland's Glass.


Offline Wuff

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Re: Question re: P15 Closepack
« Reply #3 on: April 25, 2012, 11:23:02 AM »
Attached is an image from a PP15: bubbles are definitely within the cane, and most likely on purpose.
Wolf Seelentag, St.Gallen
Interested in any aspect of Scottish glass? Have a look at Scotland's Glass.


Offline mmarc77

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Re: Question re: P15 Closepack
« Reply #4 on: April 25, 2012, 02:28:31 PM »

Offline KevinH

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Re: Question re: Cane in a Strathearn P15 Closepack
« Reply #5 on: April 25, 2012, 06:40:25 PM »
I may be incorrect, but I do not believe that air in bubbles in any regular Scottish canes were set deliberately.

To make sure that each cane slice has the appropriate air bubbles, then the relevant parts of the overall cane would have to be either truly hollow (just air, no glass), or alternatively, every slice from the main pull would have to be "pricked" with a minute tool in order to create a "pocket" over which an air bubble would form when the clear glass of the dome is added.

The latter of those options would be unthinkable! Pricking every cane slice individually would be one of the most intricate, time consuming and expensive jobs in the whole paperweight making process.

The former option - using a truly hollow cane - would be too difficult to control in all the various processes of forming a complex cane and then using it in the eventual weight. It would more likely to collapse rather than hold its shape. However I do know of a glass maker who had made some truly hollow canes (tubes) but they were used singly, not as parts of a complex cane, and the resulting air bubbles at each end of the tube were much larger than the tiny ones seen in normal paperweight usage.

I think what has happened is a normal effect of certain parts of a given cane producing minute indents at specific points during some part of the making of the cane or the weight. It may be that a particular colour reacts to its surroundings such that the various heating and cooling processes give rise to slight stretching or compression, or even minute cracks of particular parts.
Then when the cane is encased in the glass of the dome, the indents, cracks or whatever have enough trapped air to form a tiny bubble. And those effects could happen regularly for each cane slice, giving the impression of a "designed feature".
KevinH

Offline mmarc77

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Re: Question re: Cane in a Strathearn P15 Closepack
« Reply #6 on: April 25, 2012, 07:15:08 PM »
Thanks for the input Kevin. I have very limited knowledge of weights and I defer to your expertise. Your theory makes sense but surrounding the canes the bubbles are of significant size and uniformity in every one of the 12-18 or so of these specific canes I've viewed. I have yet to find that specific cane without the bubbles. Would minute indents during the making of the cane really create such consistency and fairly large bubbles? Also, when the canes are placed in the glass of the dome would the glass maker plan for the bubbles in their spacing of the cane in the closepack? The ones I have seen clearly allowed for the cane AND bubbles in the spacing. Without the bubble ring there would have been a huge gap in the closepack weight in every instance. I'm certain you're correct I'm just trying to learn.

Offline KevinH

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Re: Question re: Cane in a Strathearn P15 Closepack
« Reply #7 on: April 25, 2012, 10:30:46 PM »
Hi mmarc77,

This, to me, is an interesting topic, but exactly why air bubbles form, by chance or by design, can really only be discussed through something like a full article with plenty of photos - many of which would need to be macro closeups and from a variety of angles.

However, a few comments here may generate further thought by others which could help to explain things one way or another.

In the links that you and Wuff have given to Richard More's weights with these types of cane, I cannot tell whether what we are seeing are actually air bubbles.

In some cases, I see possible air bubbles over what looks like a very thin pale purple rod, perhaps even with a white core. The structure of many rods around a central cane design is well known, and each rod can have its own surround of clear glass as well as there being clear glass around the central section of the cane. And a cane made up of several elements may also have a final surround of clear glass, sometimes with a fairly substantial amount.

If I am correct, then the purple rod may have had a "defect" of some form which is replicated in every cane slice and which then produces a bubble over its end. This would form a very neat ring of bubbles spaced evenly to match the number of rod canes in the outer ring. Hence the uniformity that is seen.

Quote
... when the canes are placed in the glass of the dome would the glass maker plan for the bubbles in their spacing of the cane in the closepack?
Even if bubbles were a planned part of a cane, it is simply the whole of the cane, including any clear glass surround that has been added which determines how it will look within the finished weights.

For closepack weights their very nature (having closely packed canes) means that no "spacing" of canes is planned. A suitable mix of canes is set out on a small metal plate, with all the canes set as close to each other as possible. Any cane with a clear glass surround will naturally form an apparent space between its neighbours. A gather of clear glass is pressed down onto the setup to pick all the canes up in one go. Sometimes this will cause canes to move, but the glass of the gather will fill any space created. After some initial shaping, the main dome of clear glass is added.

And yes, minute indents, cracks and so forth, however they are created in a cane, can give rise to what seems to be a "fairly large" air bubble. We see the cane though its clear dome - which acts as a magnifier, and any air bubble with its globular shape will appear larger than it actually is.

Wuff's PP15 cane
The example cane that Wuff has shown from his PP15 weight, clearly does have uniformly set air bubbles. But without a detailed description of that cane, I cannot adequately comment on how the bubbles have formed. If there is no "rod" or similar element beneath each bubble, then I would be looking for a "defect" of some type.
KevinH

Offline Sach

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Re: Question re: Cane in a Strathearn P15 Closepack
« Reply #8 on: April 25, 2012, 11:44:38 PM »
It's pure conjecture but here is my theory on how those bubbles got there.  As the whether this was intentional... who can say? 

The core of this cane has a cog form.  If the next layer of glass over the cog shape went on a bit cold, or the pipe was held a bit too horizontal when gathering from the furnace, then a small bubble could be trapped in the concavities between the teeth of the cog.  When the glass goes to be stretched into a cane the air bubble is stretched along with everything else.  The result is a cane with a perfectly spaced set of tiny bubbles around its core.  This is similar to the way thermometer tubing is made.   Similar small "tubes of air" within a cane are a common problem when working bundled canes to create a complex cane.  They happen anytime the glass was inadequately heated / worked to fully fuse the bundle.

Confused yet?


Offline Wuff

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Re: Question re: Cane in a Strathearn P15 Closepack
« Reply #9 on: April 26, 2012, 09:09:15 AM »
Here's another cane from the same PP15: due to the lighter "background" of the bubbles more difficult to photograph - oblique view, as bubbles don't show up in straight-on view at all.

I cannot see "air tunnels" - which might be due to a black paperweight base, i.e. no light shining through. However, on close inspection it does more look like bubbles forming on the cane surface. The regular arrangement makes it look on purpose - but then, I have no idea either, how this could be accomplished (with reasonable effort).

Could it be different expansion coefficients of the different colours with temperature? Flat surface when canes are cut (at room temperature), resulting in a "dune surface" when heated up during set-up and encasing, and bubbles forming in the "valleys"?
Wolf Seelentag, St.Gallen
Interested in any aspect of Scottish glass? Have a look at Scotland's Glass.

 

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