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How to Choose a Glass for Kilnforming

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

How to Choose a Glass for Kilnforming

Postby cpetrauskas » Fri Dec 16, 2011 11:26 am

Watch the Lesson at:
https://videos.bullseyeglass.com/videos/how-to-choose-a-glass-for-kilnforming/

Please discuss and comment in this thread.

Thanks!
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Re: How to Choose a Glass for Kilnforming

Postby Lschnellinger » Wed Dec 12, 2018 7:18 am

In the “Compatibility” segment of this video, it is emphasized that having the same COE does not determine compatibility. The narrator says that this topic is so important that an extensive video will be dedicated entirely to explaining “what COE is and how it relates to compatibility.”

I did find the Technote 3, which is very helpful. But is there a video?
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Re: How to Choose a Glass for Kilnforming

Postby marykaynitchie » Wed Dec 12, 2018 10:43 am

Hi L,

We don't have that video yet, but here are some classic blog posts that you might find informative. These were written by Lani McGregor in 2007, to address the incorrect usage and misunderstanding of the term COE in the art glass industry.

http://www.bullseyeglass.com/blog/2007/ ... f-the-fun/
http://www.bullseyeglass.com/blog/2007/ ... un-part-2/
http://www.bullseyeglass.com/blog/2007/ ... un-part-3/
http://www.bullseyeglass.com/blog/2007/ ... un-part-4/

I hope this helps!

Mary Kay
Mary Kay Nitchie
Bullseye Glass Co.

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bit.ly/BullVideos
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Re: How to Choose a Glass for Kilnforming

Postby Lschnellinger » Sun Dec 23, 2018 2:09 pm

Those blog posts are great - thank you!

After reading the final post, though, I want to be sure I understand the relationship between COE and viscosity.

She tells the story of the blue and purple streaky glass that combined an opal and a transparent, and kept breaking. Matching the COEs didn’t stop the breakage; making the COE of the opal lower did. But she doesn’t explain why that was the case.

In comments, she says that viscosity is more important than COE for compatibility. She never specifically explains how viscosity figured into solving the streaky glass problem, but I infer that making the COE of the opal lower adjusted its viscosity in such a way that the two glasses were then compatible. Is that correct?

She says in comments, “Our experience indicates that you can be off by as much as 10% in expansion difference, but not more than 5% in viscosity.”

In the videos about drop rings - the point is made that differences in viscosity will cause glass of one type or color to drop more rapidly than another. But, since they are all “Bullseye compatible”, does that mean a difference of less than 5% in viscosity would still cause a big difference in how fast the glass drops?
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Re: How to Choose a Glass for Kilnforming

Postby marykaynitchie » Thu Dec 27, 2018 9:55 am

Yes.
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Bullseye Glass Co.

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bit.ly/BullVideos
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