Glass questions

[SusanHyatt]

Hi All,
I need to order some glass and had some questions. Once a long time ago an instructor mention 3mm double rolled was the best to use in his opinion. Can any of you tell me what are the most common uses for the different types of glass

single rolled ?
double rolled ?
thin ?
3mm ?
6mm?
anything else?

I have been using 2 pieces of 3mm double rolled in my projects so far.

Thank you,

Susan

[Bert Weiss]

Susan

As a designer it behooves you to understand the general properties of glass. I suggest spending time at the Bullseye technote site. The things they teach you there are applicable to glass beyond theirs alone.

There are 2 factors at work with your question, texture and thickness. If your design goal is to trap bubbles between layers, then the single rolled glasses will be better for you as they are less smooth. My point being that there are not universal answers as to which are "best". Thickness is a fascinating issue. Glass thinner than 6mm will dogbone if over fired. Glass thicker than 6mm will spread if over fired. The 6mm story is not simple though. Some "3mm" sheets of glass are not exactly that thickness. Some sheets thin out in the middle. So, 2 layers of this glass might still dogbone. Glass with sections of 3mm glass and 6mm glass, will tend to blow out holes if overfired.

Irridescent coatings help protect the glass from picking up schmutz from the kilnwash or fiber beneath it when fired hot. This can be a huge help, and yields different looks on each side of the finished glass.

[Morganica]

Best to use for what? Depends on what you're trying to achieve. A 6mm-thick work made with 6mm sheet glass tends to have a lot fewer bubbles than the same work made with 4-5 layers of thin glass. OTOH, a 6mm work made with 6mm-thick glass is going to be a single color with only decoration on top, while the piece made of thin glass has many more design options. So your design will influence the types of glass you should buy (and vice versa).

In terms of single- or double-rolled, there's an advantage to using double-rolled in that the smooth side's a bit easier to cut and there's less chance of trapping bubbles if you place your pieces of glass smooth-to-smooth. Neither single- or double-rolled is as easy to work with as machine-rolled, which is as flat as window glass.

The bigger deal, though, is what forms the manufacturer makes in the color/coatings you want, and what's available in your area. 6mm glass may not be available in all colors, for example.

I'm lucky in that there are two glass stores, two glass factories and a Bullseye Resource Center (which is open 7 days/week) within 15 minutes of my house, and if I care to drive a couple of hours I can add all the glass makers/shops in Seattle, too. So I can pretty much decide on whatever form of glass I want and know I can have it within an hour or two. If your only glass store in a 50-mile radius has a limited selection (and even some mail order places have this problem), you can't be that choosy.

[SusanHyatt]

Thank you Bert.

[SusanHyatt]

Morganica thank you so much. I guess for the time being will stick to what i have been using. I have a small work shop and I am toying with the idea of using 96, a supplier fairly close to me has BE90 and S96 in stock but the 96 seems to be a little less expensive. I just do not have a lot of space and know I can not let them get mixed together.

[Delberta D]

Morganica, I am curious, I live by Seattle and I didn't realize they manufacture fusing glass here. I have a couple of retailers that I go to. I always come down to Oregon for the BE sales and I purchase little in between.

[Delberta D]

It would be great to have information on locally manufactured glass. Thank You.....

[Valerie Adams]

there's less chance of trapping bubbles if you place your pieces of glass smooth-to-smooth.

Cynthia, is this what you meant to say? I've been told by several folks at Bullseye that the textured side of their glass allows bubbles to escape, so the layup should always be "smooth side up, smooth side up", which puts the textured bottom against the smooth top in a two layer piece.

I used to use Uro machine rolled as my base, but in side by side comparisons, I have to agree that I get fewer bubbles and smoother top surfaces with Tekta as a base.

[Morganica]

Val, in the tests I've run I've seen fewer bubbles with smooth to smooth, but I can see the other side of the argument, too. I think a lot depends on technique, the design, and possibly whether the particular sections of glass provide a route to the edge.

I've gotta admit that when I'm actually making something and not playing around I don't pay much attention to which side goes where. I figure that good bubble management practice (i.e., effective bubble squeeze, chadding and/or making sure you're not trapping air with your design, etc.), will overcome any disadvantages of that practice. In any case, I'm more than willing to be talked into smooth-to-rough...

OTOH, most all the clear I use is machine-rolled unless I just need 1401 for something special; I just prefer working with it.

[Morganica]

Morganica, I am curious, I live by Seattle and I didn't realize they manufacture fusing glass here. I have a couple of retailers that I go to. I always come down to Oregon for the BE sales and I purchase little in between.

There are at least five art glass manufacturers in the northwestern US (that I know of--there are probably more than that). In terms of fusible glass, Bullseye and Uroboros are in Portland. Spectrum is just south of Seattle. If you're into torchworking, especially borosilicate torchworking, Northstar and Glass Alchemy are in the Portland area and Momka is up near Seattle.

I wasn't limiting it to fusing glass, though: I also use casting glasses by Gaffer, Reichenbach and (very rarely) Schott, and those are sold (but not manufactured) in Seattle. Gaffer's US headquarters is up there, and Schott/Reichenbach are available through Olympic Color Rod.

[Delberta D]

Thank You, does Uroboros have sells like BE. They have very nice clear glass with no bubbles, It makes a beautiful cap. I have looked for sales for them but have never found one. I haven't used Spectrum for fusing because I started out with 90 COE. Not really realizing there was a more local company.

[Saracen]

Bert you wrote

Glass thinner than 6mm will dogbone if over fired. Glass thicker than 6mm will spread if over fired. The 6mm story is not simple though. Some "3mm" sheets of glass are not exactly that thickness. Some sheets thin out in the middle. So, 2 layers of this glass might still dogbone

Whilst I've only done two firings in my new kiln, both using Spectrum 96, I've had it happen on most pieces, what is a recommended solution to try and avoid it. I can't recall this problem with my last kiln.

[Bert Weiss]

Bert you wrote

Glass thinner than 6mm will dogbone if over fired. Glass thicker than 6mm will spread if over fired. The 6mm story is not simple though. Some "3mm" sheets of glass are not exactly that thickness. Some sheets thin out in the middle. So, 2 layers of this glass might still dogbone

Whilst I've only done two firings in my new kiln, both using Spectrum 96, I've had it happen on most pieces, what is a recommended solution to try and avoid it. I can't recall this problem with my last kiln.

Dogboning is a function of heat work. That is a combination of time, temperature and the quality of heat being absorbed or emitted from the kiln walls and other mass in the kiln. You can try and avoid this by not firing so hot or so long.

The general rule with dogboning is that it happens when the glass is thinner than 6mm. Here is a catch. Spectrum sheets tend to be thinner in the middle and thicker towards the edges. If you use 2 layers of this thinner section of glass, you do not get to a thick enough profile to avoid dogboning. Spectrum sells their glass by the square foot so this benefits their business model. Bullseye, on the other hand, sells their glass by the pound, so their business model is benefitted by keeping their sheets consistent. Bullseye costs more, but not 1/3 more, so the need to go thicker than 2 layers becomes part of the paradigm when deciding which glass to use.

When glass is thicker than 6mm the tendency is the opposite, and the middle spreads out when it gets soft.