Glass Message Board
Glass Identification - Post here for all ID requests => Glass Paperweights => Topic started by: Wuff on April 10, 2011, 07:10:02 AM
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This Owl paperweight (http://cgi.ebay.ch/ws/eBayISAPI.dll?ViewItem&item=360356955999) is on auction at ebay right now (images with seller's permission): upon enquiry the seller confirmed that a dent could be felt through the felt, i.e. an opening to a cavity. How was this cavity created? My interest in this weight arouse from a similar paperweight in my collection - due to the number of images allowed per posting I will post my images in the next post.
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So, here's my skull paperweight, based on computertomographic (CT) images of an actual human being. The last image was taken through the opening in the base. Base diameter is 90 mm, height 65 mm, and weight 696 g.
Which technique was used? The "lost wax technique" (or more general "investment casting") has been mentioned to me. Now checking books and the internet on these I understand how this works for outside shapes, or simple inside shapes (like some vases), where the cast can be pulled out. Just pulling out will obviously not work, however, for a structure like the skull, where glass would fill in sort of ducts within the cast.
I know from medical applications that 3D models can be built from 3D data sets (like CT images): is there some material for this, which is sufficiently heat resistant to be used as mold for glass - and then be dissolved chemically?
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:huh:
I thought that using the lost wax technique, the wax melts and runs out - but I can't quite see how in these fascinating bits - there doesn't seem to be anywhere for the melted wax to go, but I'm thinking about things from having watched bronze casting....
(I'm really not good at turning things around in my head - I always turn a map around to be in the correct direction for where I'm facing. It's a gender thing.)
You'd start with a model of the shape, then make a "negative" of it in plaster to include the final shape of the weight. Then you "cast" that from the negative in wax...... and now I'm afraid my fogged brain has refused to work out where we are, but I think it would work - there might be one stage more used for glass than for bronze......
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:hi:
Still tying my brain in knots, but I think what you need to end up with is an inflammable outer thing containing a solid wax effigy of the weight as it should be when finished, and a space to pour the hot glass into it, to melt and remove the wax. The inflammable outer thing is then chipped off to reveal the weight.
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There is a beautifully illustrated description (http://bestinpackaging.wordpress.com/2010/12/15/the-making-of-an-exceptional-glass-bottle-the-lost-wax-technique/) of the lost wax technique to produce a Lalique whisky bottle - but only describing (unless I miss something) how to produce the bottle. The stopper looks somewhat similar to the two paperweights above - but I don't find a description how this is actually done.
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Thanks very, very much for posting that link Wuff - fascinating!
(and the Macallan is, of course, completely worthy of the glass; the time, the trouble and the expense. :sc: )
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There is a beautifully illustrated description (http://bestinpackaging.wordpress.com/2010/12/15/the-making-of-an-exceptional-glass-bottle-the-lost-wax-technique/) of the lost wax technique to produce a Lalique whisky bottle - but only describing (unless I miss something) how to produce the bottle. The stopper looks somewhat similar to the two paperweights above - but I don't find a description how this is actually done.
I was just informed by the site author that the building in the stopper was cut. Could the owl also have been cut? The structure looks much less complicated than the skull - I'll have a closer look when the owl arrives at its new home ;).
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It's very hard to tell from a picture, but I don't believe these paperweights were produced using a "lost wax" technique. Generally, a lost wax process will yield a "positive" image when working with glass or metal. These appear to be negative images. I believe they were produced by reverse sand carving a solid glass blank. That's only a guess though as I wasn't able to find any other examples on the web.
Regards, Larry
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Could laser etching be a possibility? they're usually not hollow, but the detail on the skull reminds me of that a little.
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I was just informed by the site author that the building in the stopper was cut. Could the owl also have been cut? The structure looks much less complicated than the skull - I'll have a closer look when the owl arrives at its new home ;).
The owl has now been sitting on my desk for a while - but I'm still not sure about the production method. I feel it could well have been cut or by reverse sand carving (as suggested by Larry) - but not laser etched (too much material removed - which also applies to the skull).
I still have no clue about the skull, as the detail proves to me that the actual CT images were used for some sort of computerized production method. Any further comments welcome!
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it looks like the same way they do engine blocks.... could of been done with highly compressed powder in a mould, take the mould apart and the effigy of the owl is there.... pour molten glass on top shape it and wait till it has cooled add water or vibrate to dissolve the powder and hey presto ..... that's just my theory
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I've just been to the exhibitions currently on in Perth Museum - the Caithness one, Loch, Heather & Peat, but there is also "Trove", an exhibition organised by the Scottish Glass Society on, showcasing the work of 25 contemporary artists.
A couple of them have made things which are very similar to your weights - with hollow insides of strange and complicated shapes.
There is an image of one by Elizabeth HH Cull on her website here (inspired by corals) which I have just seen, and it is described in the exhibition as being "a kiln formed positive air sculpture using the lost wax technique"
http://www.elizabethcullglass.co.uk/
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These look to me very like Anne Arlidge's (Assenden Glass) 'Lost Vegetable' castings. As I understand from Anne, the vegetable (or fruit, or fish) burns away when the clay mould is fired, and then the void is filled with molten glass. All that would be needed was to then case the resulting item in a layer of clear glass and you would get the result seen here with the owl and skull!
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I thought Wuff's weights had hollow insides. :spls:
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i dont think wolfs weight has been done with the lost wax technique