Topic: cracked Ysart

[Fuhrman Glass]

tunnel lehrs for paperweights and thicker pieces of blown ware are a real problem. It's hard to get them to run slow enough and also those pieces normally require a hold time at the annealing temp before they are started to come down to room temp.
The fact that borosilicate glass and soda lime glass were being used and made in the same facility also makes for a lot of problems as boro has a very low COE compared to soda lime glass and also is normally annealed at a much higher temp. The boro also requires higher temps for working the glass. Not sure what their boro was like but pyrex is worked closer to 3000 degrees F, while soda lime is worked closer to 2100-2250 F.
Switching from one glass to the other for the gaffer can be a little tricky at times.
Enjoyed looking at all the work you and others have done on the Ysart's and related Scottish glaasworks, definitely had to be a labor of love.

[Frank]

There was no boro used in the art glass and the actual formula they used is unknown. The annealing cracks in the glassware are invariably very short, outer casing only, and concentrated on flatter surfaces and tight curves also on the inside under knobs on lids. Generally not visible to the naked eye.

As far as I am aware that corner of the works was exclusive to the Ysart men too. No one was allowed to even come close when they were working in their corner.