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Frit compatibility

Posted: Wed Jan 05, 2022 9:45 am
by Jon Markovic
I have read about the need to use compatible glass in a kiln, because mixing glass with different rates of expansion creates stresses that can cause work to crack.
It would seem to me that this is particularly relevant to larger pieces of glass with greater surface contract where stresses can form.. but perhaps less so when glass particle size is smaller.
So I've been wondering whether compatibility is such an issue where frit is used, and particular so when the frit is not fully fused (and adjacent frit pieces melt together to form a larger whole) into the base.
Any thoughts would be appreciated!

Re: Frit compatibility

Posted: Fri Jan 07, 2022 11:12 am
by Kevin Midgley
Three Words.
Don't Do it.
Known differences will result in tiny cracks of incompatibility around the offending bits.
These could cause the piece to later break completely years later.

Re: Frit compatibility

Posted: Sat Jan 08, 2022 7:06 pm
by Tom Fuhrman
I've had pieces the size of a pinhead that when encased caused a piece to crack. There is always a chance of a piece cracking when combining different glasses even though they are theoretically the same COE. Dan, the owner of Bullseye has written some very good pieces on compatibility and I think they can be found on the Bullseye website. COE is not the only factor that determines if two glasses will be compatible. Viscosity also has a very important part in those determinations.

Re: Frit compatibility

Posted: Thu Nov 24, 2022 9:13 am
by Tom Stout
I am a newcomer and very happy that there is a forum for WARM GLASS artisans! My mother - in - law blew glass for over 40 years @ Toledo Museum of Art and Crosby Gardens. She accumulated a large inventory of different colors of frit, from very fine to long, fat, color rods. CR Loo was her vender and most of her frit seems to have a COE of 87 +/-. She never threw anything away which included anything she blew that annealed improperly or via incompatibility, fractured two weeks after she brought it home. She in fact is the reason I got into not only stained glass, but within the past 15 years, warm glass. One of my biggest "unanswered" questions I have posed to not only her but others in the hot glass arena is: What was the COE of the vat glass used on a daily basis in the glass studio in which she spent so much time????? Surprisingly, I have never gotten a straight answer. Most of her rejects I have in my warm glass studio, waiting for a "new life." Some days her frit worked with the vat glass, other days it did not. Bottom line for this post.... my own experience has found that Bullseye glass is more compatible with the frit that I use, all of which belonged to my mother in law from CR Loo. Mixing it with Spectrum (COE 97) does not work out well. Mixing it with Bullseye is a more compatible combination. Unless it is clearly marked COE 97, I assume it is COE 87 (CR Loo). I hope is post is useful information.