Topic: Perthshire glass COE is what?

[alpha]

Any one know the COE on Perthshire Paperweights glass? Is it 104?

[w8happiness]

Hi Alpha,

the expansion coefficient (104) you mention is more often found for Murano glasses, the Effetre glass for instance; I have had some Effetre millefiori canes fused into borosilicate glass and the canes promptly blasted and split the boro dome while annealing...the glassmaker was surprised, but said that Murano glasses are made of "light" Soda lime glass and there are difficulties in embedding this type in other glasses. Perthshire glass has a SG of +-2,6 and therefore must have a little higher lead content as Murano glasses to prevent the enclosed colours from imcompatibility...

New boro artists (esp. marbles!) have overcome a lot of those difficulties- have a look at Brian Bowden's site GlassOrbits...
I also think that the exact Perthshire coefficient and formula will depend on much experience- and surely kept as maker's secret...    Kind regards  E.

[Sach]

Any effort to fuse 104 glass to borosilicate is doomed to dramatic failure.  The properties of the glasses are not similar in any way.  Thermal expansion is not the only factor in glass compatibility even though it is the best known and most often mentioned.