early 1900s PATE DE VERRE

[rodney]

here on the board we discuss coe alot, but what about the glass that was made in the early 1900s, i cant imagine they knew as much about this as people today, but the glass is still around and not broken from stress,,,,,,when it comes to dealing with small frit, is coe not as much of a consideration,,,,thanks
rodney

[Bert Weiss]

here on the board we discuss coe alot, but what about the glass that was made in the early 1900s, i cant imagine they knew as much about this as people today, but the glass is still around and not broken from stress,,,,,,when it comes to dealing with small frit, is coe not as much of a consideration,,,,thanks
rodney

Rodney

Not true at all. Much of the early pate de verre was made with one kind of glass and some oxides for coloration. This would be all compatible glass, as glass is compatible with itself and the oxides didn't change it enough to effect COE enough to make it crack. Once there is a significant layer of glass COE is going to make it break or crack if there are big enough differences in the wrong places. Forces of stress are forces of stress.

[Nikki ONeill]

The pate de verre formulas used at the turn of hte century were high in lead content, a mix less sensitive to stress. I thought that their glass also flowed and melted at lower temperatures, too, making it much easier on plaster molds. Does anyone know if a very low melting temperature leaded batch is available? Perhaps mixing that with kugler colors would make a nice pate de verre mix. Has anyone used the leaded frits from Ferro or Pemco in a pate de verre glass mix? Or aded them to BE? I stumbled across a ceramaics glaze book and the possibilities for glassy colors and glazes are boggling. Seems someone would have optimized a mix for pate de verre.
Nikki

[Brad Walker]

Bert is right. The early pate de verre artists didn't use the same kind of colored glass we use. They started with a base glass that was colorless and added oxides to get the color. Argy-Rousseau, for instance, mixed chalk, feldspar, kaolin, and boric acid, heated it to 1250C/2280F, then added oxides for the color (cobalt for blue, brass for light turquoise, chromium oxide for green and dark yellow, gold for purple-pink, etc.) He would also add lead to reduce the fusing temperature. Since all of these different mixtures started from the same base glass that was just broken up and mixed with the various oxides and other chemicals, compatibility wasn't really an issue.

Each of the early pate de verre artists had their own formulas for glass and for molds. Argy-Rousseau, for example, made his molds from plaster, kaolin, sand, and asbestos. The pdv artists also often packed their molds with asbestos to keep the glass from moving, another practice we'd probably not want to emulate.

[Brad Walker]

The pate de verre formulas used at the turn of hte century were high in lead content, a mix less sensitive to stress. I thought that their glass also flowed and melted at lower temperatures, too, making it much easier on plaster molds. Does anyone know if a very low melting temperature leaded batch is available?

Gaffer makes a good casting glass: http://www.gafferglass.com It does have some lead, and melts a bit lower than BE or System96.

You're right that the pdv artists just added lead to their regular glass mixture. Generally 24% or less lead was considered pate de verre, while 45% or so was considered pate de cristal.

[Lauri Levanto]

I have no historical sources, so I can't debate what they really did.

Lundstrom mentions a possibility to recirculate glass. He grinds it very small, mixes thruout and apparently melts for a longer time. The result is a "new" glass with a COE that is an average of sources.

In Pate de verre the same thing happens. If you use one
base glass, add colored fine powder in small proportion,
the stress is there but distributed so that local stress anywhere is minimal. Especially if your base glass conteins
some strong flux like lead that aids in homogenisation.
The same happens when glass blowers use their base glass,
marver color frit on it and blow the color so thin it does not
concentrate stress.

Strong local concentrations of non-compatible color will cause truble!

I HAVE NOT TRIED it yet. The risk is yours.

-lauri