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Making Part Sheets

For discussion and commentary regarding the Lesson and Project videos of the Bullseye Kiln-Glass Education Online program.

Making Part Sheets

Postby Chris_Petrauskas » Thu Dec 13, 2012 10:12 am

Watch the Lesson at:
https://videos.bullseyeglass.com/videos/making-part-sheets/

Please discuss and comment in this thread.

Thanks!
Chris Petrauskas
Bullseye Glass Co.
Portland, Oregon, USA
http://www.bullseyeglass.com
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Re: Making Part Sheets

Postby jdepaula » Sun Jun 08, 2014 3:11 pm

I enjoyed the lesson - lots of interesting things to try.

But I had a question. I'm not sure I understood how you can make a part sheet that is 3mm thick. Clearly you are going to full fuse on these (1425-1480F).

Why doesn't the part sheet pull in and puff up to 6mm?
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Re: Making Part Sheets

Postby bethLkeyser » Fri Nov 21, 2014 8:43 am

I too am confused about how only one sheet of glass can be fired to form a part sheet. I work with COE96. Could you explain?
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Re: Making Part Sheets

Postby Chris_Petrauskas » Mon Nov 24, 2014 9:58 am

John, Beth,

You make good a good point inquiring about the "6mm rule" but, practically speaking, in this application it's not a significant concern.

Yes, it is true that the natural surface tension of glass in its liquid phase will tend to pull it towards a thickness of 6mm.

That process however is heavily modulated by, among other factors, the viscosity of the glass (dictated by process temperature) and surface drag and will take quite a long time to act on the large-ish sheets we're working with. You'll notice that about :30 into chapter two we mention that you should leave a 15mm allowance at the perimeter of the sheet to trim. This is because the contraction will have started there but because of the relatively brief period of heat-work at fusing temperatures, it doesn't cause very much distortion.

So, for the types of designs and firing schedules we show in this video, you can consider the final trimmed part sheets to be nominally 3mm.

Chris
Chris Petrauskas
Bullseye Glass Co.
Portland, Oregon, USA
http://www.bullseyeglass.com
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