Topic: PY bubbles

[Roger H]

Hello, a question I have been asking myself for a little while is, in Paul Ysart weights of the 1930s how long did it take before the multitudes of tiny bubbles present in the early weights to be reduced to very acceptable levels?     I dont even know what really causes them.
          Regards Roger.

[Roger H]

OK, what causes the bubbles, surely somebody knows who worked in the glass making industry earlier in their life.
      RHW

[mildawg]

Air causes the bubbles or maybe its error that causes them.

[Roger H]

Yes I guess air would be involved in air bubbles and the early technique of picking up from the hotplate another.  I can understand air getting trapped between the two converging glass parts, but why so many?
     RHW

[mildawg]

Honestly I think the great majority in a piece like this is possibly the haste with which the piece was made. A sloppy gather of glass and then forming would trap the air. The small bubbles at the point where the two surfaces meet could be due to dirt or slight condensation I suppose from temperature difference in the glass, I don't know if it would be the result of some reaction or not. I wouldn't think so.

[Sach]

The most likely answer is dirt and oils on the set-up.  I'll wager the folks doing the set-ups were using their hands rather than tweezers.  You need to clean the cane before you cut it, catch it in a very clean surface and never touch it again.  A cold cover gather can result in poor penetration of the glass into the spaces between the canes.  This tends to cause larger bubbles than what we see here.  Modern glass workers frequently use vacuum to help reduce this problem.

[Roger H]

Thank you, interesting probabilities, impurities makes sense either dirt,oil, hand grease or water for the tiny bubbles.
       Roger.

[KevinH]

I'll wager the folks doing the set-ups were using their hands rather than tweezers.

As far as I know, 1930s Paul Ysart weights were set up by Paul (although I suppose he may have allowed an assistant to gather some fresh clear for the dome).

However, I agree that the mass of tiny bubbles that do sometimes appear in earlier PY weights is a result of such as contaminants of some form or just different temperatures of the parts resulting in not all of the minute spaces between, around, and upon canes being filled completely with glass.