Hi everyone...another neophyte here!
So far have been working exclusively with float (not because it is cheaper...but cuz it is free...we own a demolition business) until I get better at this.
I have several questions here...
First: is it possible to have an overlapping of compatibility between glasses?...I have been testing what appears to be at least 3 different "ranges" of COE. but there is this blue glass that seems compatible across the board with glass that are not compatibile with each other (does that make sense?).
Second: I am about to refire some testers that did not fuse completely last firing. My understanding is that glass becomes "softer" with each firing so will this affect the reliability fo this test? Or should I start all over?
Third: Does size matter? Can you use any size "chip" to test or if it is too small will it give you a false compatibility?
I am firing in a too large pottery kiln...that's all I have...firing up to 5 sometimes 6 shelves to justify the cost. Generally works out, but boy, after following this bulletin for awhile I don't know how or why!
But I do love the board!.....Thanks from a Hawaiian Downunder!
? re: Compatibility testing of float
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Bert Weiss
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kl
The simplest answer is that glass is always compatible with itself. If you have a large sheet, cut it up and fuse it to itself.
Once you are trying to fuse random sheets of unknown glass, you are in for some surprises. Personally I don't like surprises.
That said, you can do compatibility tests just like with Bullseye, and it only takes a small chip to test with a polarizer. Another test is the strip test. Cut 2/ 1" x 12" strips and fuse them together and see if it warps. The more it is warped, the bigger the compatiblity difference. Somewhere there is a chart where you can actually measure the differences.
With 6 shelves, you run the risk of 6 different temps, so you are in complicated territory relative to both top temp heat work and to annealing.
The simplest answer is that glass is always compatible with itself. If you have a large sheet, cut it up and fuse it to itself.
Once you are trying to fuse random sheets of unknown glass, you are in for some surprises. Personally I don't like surprises.
That said, you can do compatibility tests just like with Bullseye, and it only takes a small chip to test with a polarizer. Another test is the strip test. Cut 2/ 1" x 12" strips and fuse them together and see if it warps. The more it is warped, the bigger the compatiblity difference. Somewhere there is a chart where you can actually measure the differences.
With 6 shelves, you run the risk of 6 different temps, so you are in complicated territory relative to both top temp heat work and to annealing.
Bert
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Bert Weiss Art Glass*
http://www.customartglass.com
Furniture Lighting Sculpture Tableware
Architectural Commissions
Thanks for the reply, Bert.
, but as I say, at the moment that is all I have and I do like to, and have had many successes, using different coloured glass. My understanding is that here in Australia there was only a limited number of companies making glass - one per state, so I'm told, and there are only 8 states here in this huge country. I live on a border so I'm only dealing with 2-3 manufacturers so theoretically I should really be dealing with 3-4 different COEs, similar to the 3-4 companies of art glass. So persevere, I must, and as I said so far most of what I have worked out as compatible has worked out in the finished product...but certainly not without "surprises"! (In fact, it's like Christmas everyday here!!)
I knowThe simplest answer is that glass is always compatible with itself. If you have a large sheet, cut it up and fuse it to itself.
, but as I say, at the moment that is all I have and I do like to, and have had many successes, using different coloured glass. My understanding is that here in Australia there was only a limited number of companies making glass - one per state, so I'm told, and there are only 8 states here in this huge country. I live on a border so I'm only dealing with 2-3 manufacturers so theoretically I should really be dealing with 3-4 different COEs, similar to the 3-4 companies of art glass. So persevere, I must, and as I said so far most of what I have worked out as compatible has worked out in the finished product...but certainly not without "surprises"! (In fact, it's like Christmas everyday here!!)You're not wrong! Which is why I stand in front of the kiln for days with various work splayed out in front of me just trying to calculate where and how exactly to put each piece on a shelf and where exactly to place each shelf in the kiln. 6 shelves is extreme and really I keep it between 4-5 shelves, which I know is still extreme....but I feel like I'm getting the hang of it while on this steep learning curve! But definately complicated...With 6 shelves, you run the risk of 6 different temps, so you are in complicated territory relative to both top temp heat work and to annealing.
Anybody on the other two questions?....please??First: is it possible to have an overlapping of compatibility between glasses?...I have been testing what appears to be at least 3 different "ranges" of COE. but there is this blue glass that seems compatible across the board with glass that are not compatibile with each other (does that make sense?).
Second: I am about to refire some testers that did not fuse completely last firing. My understanding is that glass becomes "softer" with each firing so will this affect the reliability fo this test? Or should I start all over?
kl
no.First: is it possible to have an overlapping of compatibility between glasses?...I have been testing what appears to be at least 3 different "ranges" of COE. but there is this blue glass that seems compatible across the board with glass that are not compatibile with each other (does that make sense?).
Second: I am about to refire some testers that did not fuse completely last firing. My understanding is that glass becomes "softer" with each firing so will this affect the reliability fo this test? Or should I start all over?
Anybody on the other two questions?....please??
define 'softer'. the coe does and can shift, but which way it shifts is different for each type of glass.
no.
Thanks Charlie,
1 - "no" to what? The overlapping of compatibility or making sense?
If in regards to compatibility, then what is happening? I fused these testers over a week ago and the blue hasn't cracked or polarised on any of the glass although as I say, there are three different "groupings of compatibility".
2 - By "softer" I mean pretty much as you answered...that the glass will react at a lower temp than before. So would that mean that it would adversely affect my compatibility test? Especially if the coe can shift either way...but would that then give you more info re: compatibilty?? Or only the second time around...which might be the case if fusing then slumping in 2 different firings??? Hhhmmmm.....
1 - "no" to what? The overlapping of compatibility or making sense?
If in regards to compatibility, then what is happening? I fused these testers over a week ago and the blue hasn't cracked or polarised on any of the glass although as I say, there are three different "groupings of compatibility".
2 - By "softer" I mean pretty much as you answered...that the glass will react at a lower temp than before. So would that mean that it would adversely affect my compatibility test? Especially if the coe can shift either way...but would that then give you more info re: compatibilty?? Or only the second time around...which might be the case if fusing then slumping in 2 different firings??? Hhhmmmm.....
kl
1: no to making sense.a glass has A coe, not a range of coes. since it isn't flexible to any degree, then it isn't able to move to give way. i can't explain what you are seeing. perhaps your glasses aren't far enough apart and the overlay is in the middle. for example, if you have a 89, 90, and 91, and cap it with a 90. the 89 and 91 may not play together well, but the cap will since it's close enough to the end points, and it matches the center one.
2: it can shift. sometimes it takes multiple firings for the shift to start. for example, bullseye tests and will state that it takes at least 3 firings for a coe shift to occur in their glass. sometimes it takes more, depending upon color and glass makeup. if you don't know where yours came from, it's anyone's guess how many firings or what temp this coe shift will occur at.
2: it can shift. sometimes it takes multiple firings for the shift to start. for example, bullseye tests and will state that it takes at least 3 firings for a coe shift to occur in their glass. sometimes it takes more, depending upon color and glass makeup. if you don't know where yours came from, it's anyone's guess how many firings or what temp this coe shift will occur at.
kl
Working with COE differences - my experience and some conjecture:
How you use two or more glasses is equally important to their COEs. Successfully fusing two 3mm (1/8") or more layers of different COE next to each other, or one atop the other, is the toughest and will only tolerate the smallest COE differences. Of course other variables - thickness, shape, heating/cooling cycle - all play their part in the final result.
Glass painters often ignore COE mismatch. Thin layers of high COE color (or enamel) fuse quite well onto lower COE glass. In the firing there may be a degree of mixing at the interface of the two different COE glasses, forming a zone of intermediate COE which helps to "cushion" the different glasses to each other. Further, the thin layer of enamel may have its total composition changed significantly by mixing with the substrate at firing temperature. Equally the substrate can take on some of the characteristics of the color layer at the interface. So instead of two very different COEs right next to each other causing the maximum amount of strain, you may have an intermediate zone of variable COE allowing the two layers to live quite well with each other.
My guess this is how Ron C. successfully "hotglues" BE 90 with a low temperature frit which almostly certainly has a different COE.
I've had success mating 2 different COEs by interposing an intermediate COE between the other two. This works best when the third layer is made from finely ground glass-forming materials which encourage mixing with the other layers at the interface.
How do you alter the COE of glass? Easily if you are making it yourself. In the simplest terms there are high COE ingredients (fluxes) and low COE ingredients (silica) in glass recipes. Juggling these allows you to alter the COE of the resultant glass. Blowers who make their own pot-color do this.
Can you alter the COE of an existing glass? Sort of.
You can alter the COE of powdered glass frit in a rough-and-ready way by mixing in high COE material (or low depending on which way you want to move the resultant COE). Mixing potters' silica with BE powder frit will lower the COE enough to make it fuse OK onto float if the BE layer is not too thick. However the silica will dilute the nice BE color and you probably won't like the result.
Ralph
Not sure about past years but I think there's only one making architectural float now - Pilkington's in Victoria. However float is imported from Indonesia, China, Israel and other places. You're bound to be dealing with plenty of different COEs here.My understanding is that here in Australia there was only a limited number of companies making glass
Working with COE differences - my experience and some conjecture:
How you use two or more glasses is equally important to their COEs. Successfully fusing two 3mm (1/8") or more layers of different COE next to each other, or one atop the other, is the toughest and will only tolerate the smallest COE differences. Of course other variables - thickness, shape, heating/cooling cycle - all play their part in the final result.
Glass painters often ignore COE mismatch. Thin layers of high COE color (or enamel) fuse quite well onto lower COE glass. In the firing there may be a degree of mixing at the interface of the two different COE glasses, forming a zone of intermediate COE which helps to "cushion" the different glasses to each other. Further, the thin layer of enamel may have its total composition changed significantly by mixing with the substrate at firing temperature. Equally the substrate can take on some of the characteristics of the color layer at the interface. So instead of two very different COEs right next to each other causing the maximum amount of strain, you may have an intermediate zone of variable COE allowing the two layers to live quite well with each other.
My guess this is how Ron C. successfully "hotglues" BE 90 with a low temperature frit which almostly certainly has a different COE.
I've had success mating 2 different COEs by interposing an intermediate COE between the other two. This works best when the third layer is made from finely ground glass-forming materials which encourage mixing with the other layers at the interface.
How do you alter the COE of glass? Easily if you are making it yourself. In the simplest terms there are high COE ingredients (fluxes) and low COE ingredients (silica) in glass recipes. Juggling these allows you to alter the COE of the resultant glass. Blowers who make their own pot-color do this.
Can you alter the COE of an existing glass? Sort of.
You can alter the COE of powdered glass frit in a rough-and-ready way by mixing in high COE material (or low depending on which way you want to move the resultant COE). Mixing potters' silica with BE powder frit will lower the COE enough to make it fuse OK onto float if the BE layer is not too thick. However the silica will dilute the nice BE color and you probably won't like the result.
Ralph