Glass Identification - Post here for all ID requests > Glass Animals & Figurines

Got a technical question?

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Borolamper:
I joined to use the classifieds, so I thought I would try to make myself usefull.
I have read a great deal about glass over the years, including every fusion magasine (The American Scientific Glassblowers Society journal) from June of 1956 to November of 2002 inclusive. While my focus has been learning about borosilicate, I might have an answer for your oddball question.

Frank:
Much appreciated, here is a good one for starters that I never get round to finding out myself:

Why is Borosilicate glass the choice of lampworkers/flameworkers?

My intro to glass was handblown art glass resulting in ysartglass.com and from there the parent company that developed one of the eariler succesful borosilicate glasses for use as gauge glasses:

http://www.ysartglass.com/Indexart02.htm

Borolamper:
A low coefficient of expansion (C.O.E.) makes borosilicate less prone to heat stress. Soda-lime glasses tend to crack much more easily in the flame, but they allow for a much larger colour selection, as it is worked at a lower temperature.

Frank:
Thanks, leads to more q's... so do some people work with soda-lime mixtures instead? I know you cannot mix them due to different COE's.

Is there any easy way of distinguishing the type of glass used?

When did coloured forms of borosilicate become available?

Borolamper:
Most beadmakers work soft glass. Moretti is an example.

Assuming you are looking at a finished piece, and not at raw material you can do compatibility test with in the flame, the simplest way to distinguish between hard and soft glass is by density. Soft glass weighs 1/3 more, or hard glass weighs 1/4 less, depending on which one is considered normal. Simplest way in the flame is to take a small piece of a known glass, and an equal piece of the unknown glass, and make a blob with them overlapping. Pull this out into a thread, and watch how much it curves as it cools.

Cobalt blue has been around in limited quantities for quite some time, but generally speaking, early to mid 90's was when borosilicate colours became available. I was mixing my own colours when I started back in '93.

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