aluminosilicate glass

[full_kiln]

anyone know anything about this stuff? i hear it's mad tough to work with

[Alfred]

Schott Glass' Special Tubing Selector (http://www.us.schott.com/tubing/english/product_selector/index.html?PHPSESSID=18hbnhmdeaaa9t3cm18nid2bi4)

The aluminosilicates are Schott 8252, Schott 8253, and Schott NEO1730
The COE's are between 4.5 and 4.7

Click on the details tab then the data sheet (pdf file) for each to get their annealing,strain,softening,and working points.

Duran and Boro Artistic specs are also listed.

[JLF]

There are very few people that even need to work with it or know how to. Very shocky (prone to exploding), easily gets bubbles, easily gets dirty, expensive, not many sizes available.

There are only a few scientific glassblowers that use it and they use it usually for Helium experiments as Helium doesn't pass through it (at least not an any signifgant rate to my understanding). Helium will actually escape through borosilicate or Quartz.

The stuff really can't be re-worked with great results. Once you make something with it you are better off just leaving it as you may destroy it if you reintroduce it to the flame. You have to use strange flames, and hot ones, trying to avoid bubbles.

There really are no artistic uses for this that I can think of. Again its main purpose is for Helium applications and other gases.

Since you are in NJ, you may want to sign up for classes at SCC or join up with the ASGS if you want to learn more about scientific glassblowing. People there would have much more help.

[full_kiln]

thanks for the info, i'm already planning on going to scc for college, i was reading an article on sgt and it said that no one wants to work with it because it's so tough to work with

[NUBBLET]

with a COE of 4.5- 4.7 I dont think its very shocky , it even say high resistance to shock

[full_kiln]

i thought lower COE meant less prone to shock

[RaindropRising]

lower COE does mean lower shock in the flame because the material doesn't build up nearly as much stress when it cools down.

Thats why borosilicate is 33COE and soft glass is 104. Soda lime is 90 correct? Are there more factors that go into it?

[JLF]

I was lucky enough to have seen quite a few GE-180 aluminosilicate pieces worked over a period of time lasting only a few months. From my observations, brief times working it, and notes of my mentors it was very temperamental in regards to changes in temperature. It would explode unless treated very carefully and required a very special annealing cycle. Ovens were running and up to temp before work began because once the apparatus was complete, it was a mad dash to stick it in the oven to avoid cracking/exploding. Work it with a hydrogen flame like Quartz but watch out for bubbles, once they start it's a mess.

Because of the heat most things burn out, just like with Quartz, but for some reason 'dust' or something else in the air sometimes burns into the glass and can cause pitting and more bubbles.

With boro you need to always be aware of keeping your work hot so that it doesn't crack.

With quartz you have much more room with annealing as you can even take a molten piece and stick it in water and in most cases it won't crack.

With the GE-180, it was always in an annealing flame when it wasn't being worked and fear of it cracking was always there.

I have only seen Corning 1720 once. I made a side seal with it, looked like shit and was full of bubbles.

Those are my only experiences with the material. ASGS or scientists that need the stuff are your best resource to learn about it.

I am by no means an expert on the subject, just throwing in what I know :)

It is strange stuff.

[roger parramore]

Wash it in aqua regia, rinse with deionized water, never touch it with your bare hands, and work it in a hydrogen flame--no problem. But why bother? It is very finicky stuff with few applications suitable for lampwork artists.

[Mike Souza]

I have worked GE 180, Corning 1720, 1724 & 1723 along with Schott's 8252, 8253 aluminosilicates. Their prime use in industry is for lamps. It's a rugged seal to tungsten at much higher temperature then standard metal sealing glasses. In research we like it because it's low permeability to helium, its high resistivity and its dielectric properties make it a good envelope for high energy experiments. What makes it so difficult to work compared to other glasses, is its low tolerance to oxygen flames in general and its high transition temperature. So you need a high temperature reducing fire, which is why hydrogen can work nicely. With pyrex and other glasses you get to about 490 to 450c the glass is quite elastic and ready for transformation to its liquid phase. Furthermore, you have indicators like our sodium glare telling you when the glass is ready for the transition. With aluminosilicates your transition temps are from 690 to 750c. Bear in mind as well. the COE is about 44 and this is a linear number. So in the case of pyrex at 490 the COE has topped out, with soft glass the number is even lower. Aluminos are like the everready bunny its still running higher. To make matters worse, your sodium glare is non existent, because most aluminos are alkali free glasses. Reboil mostly occurs because gases can evolve within the glass and become trapped inside the bulk during the heat-up process. AT this point the oxygen from the flame makes matters worse.
One thing about aluminos, that gives me greater appreciation for flamework artists is its reactivity to the flame chemistry. For most of us this is an overlooked aspect all we think about is temperature and size of a flame. This glass and color borosilicates remind us in powerful ways that there's a lot of chemistry happening when we use gases on a material that becomes soluable to the flame in its liquid phase.

[FredLight]

Nice info,Mike.

That's good stuff.