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Cutting Opal glasses

For discussion of processes related to using Bullseye glass, including kilnforming and kilncasting, torchwork, blowing and stained glass.

Re: Cutting Opal glasses

Postby tommckay » Fri Jan 22, 2010 8:05 pm

I am part of an adult community & work mostly in the studio. There are about 30 of us use the studio & we are exclusive Bullseye users. All of us this past 6 months have complained at cutting white 000013-0030. Our glass is all stored in the studio at an even nice 70 degrees. We did read, and some of us know about cold glass cutting, but we are not so sure that this is the problem this time. The electric pad was very interesing solution. We would be interested to try that. I wonder what the surface temp needs to be to make cutting easier?
BTW I was vitalspark. I am not so vital now my username has changed!!
Scotland Forever !!
Posts: 52
Joined: Fri Dec 11, 2009 8:43 pm

Re: Cutting Opal glasses

Postby Lani McGregor » Sat Jan 23, 2010 8:31 am

Ach, a McKay! On the highly obscure chance that you are related to Mr Mackay the Butcher who until lately made the Glass World’s Most Beloved Meat Pies out of a small shop down the main street from North Lands Creative Glass in Caithness, Scotland, may I say I loooooove your clan!

But on a more serious note: huge thanks for reporting on your group’s experiences with 0013 white opal. This is exactly the kind of information that helps us address product problems.

For oldtimers, this won’t be news, but on the off-chance that a newbie exists who isn’t familiar with the reasons behind the differences in cutting opals vs transparents:

It is the amorphous structure of glass that allows it to be cut as easily as it is.
An opal glass is created by the controlled growing of a crystalline matrix within the body of the glass. This is essentially an early step on the road to devitrification – or the process of the material becoming an “un-glass”. Ever tried to cut badly devitrified glass? It’s a nightmare.

This is the glass chemist’s challenge: to create a glass that has started down the path of devitrification, but stops short.

Opal glasses will always be more challenging to cut than transparents, and some opals will be more challenging than others. I am going out on a limb here and indulging in some unsubstantiated theorizing, but I’d suggest that the denser an opal is, the more “un-glassy” it is and the more difficult it will be to cut.

0013 was – at users’ request – designed to be the densest of all our white opals. That density may guarantee that it will always, by its very nature, be the most challenging to cut.

That being said, we’ve made a limited number of sheets of 0013 in ¼ inch thickness from various melts of 0013. Dan has been cutting them – albeit in straight cuts – and is convinced that the cutting pressure (light vs a heavy pressure is best) is hugely more important in cutting this glass than any other factor.

Myself, I like Steve’s idea of marketing Bullseye branded heating pads.

Sorry. Didn’t mean to write a book on this. Must have been drunk on the memory of Mr Mackay’s pies…..

Lani McGregor
Posts: 30
Joined: Wed Aug 06, 2008 2:13 pm
Location: Portland, Oregon, USA

Re: Cutting Opal glasses

Postby weditt » Sun Jan 24, 2010 10:08 am

Thanks, guys. I've had the same problem cutting glass when my studio drops into the 40's. I just figured I was a mow-ron. I feel better about the yucky cuts, and got a good laugh as well! (and so did my husband, who loved the knitted tea-cozies for frit jars idea - given that the frit jars are overtaking my studio space...). In any case, I have added a heating pad to my list of art supplies I need to pick up. (I live out in the boonies - nothing is convenient, except my garden). If it weren't for internet, I could never enjoy playing with glass.


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