11-03-2016, 09:43 AM
The glass becomes very brittle with age & heat.
Here's a tip - score all the way round the valve, cleanly in one joined up line - do so as close to the biscuit (the bit with the wire/pin feedthroughs) as possible. Then wipe the scored groove with WD40 and with the valve wrapped up in something protective and wearing eye protection & gloves, tap gently around the score with the end of a decent screwdriver. The "hot wire" (W or NiCh) technique is also very good for tubular work - lots of videos about this online.
The WD40 (or paraffin) is a trick given me by a hot glass worker (no innuendo please!) - for some reason the breaks are always cleaner, but old glass is always more difficult to work with than new - I also do neon sign work, and old glass is not good stuff to handle - new is easy to snap cleanly.
I would certainly "gas" the valve by breaking the nipple before attempting to decapitate it.
See: http://www.teralab.co.uk/Glass_Blowing/H..._Page1.htm
Here's a tip - score all the way round the valve, cleanly in one joined up line - do so as close to the biscuit (the bit with the wire/pin feedthroughs) as possible. Then wipe the scored groove with WD40 and with the valve wrapped up in something protective and wearing eye protection & gloves, tap gently around the score with the end of a decent screwdriver. The "hot wire" (W or NiCh) technique is also very good for tubular work - lots of videos about this online.
The WD40 (or paraffin) is a trick given me by a hot glass worker (no innuendo please!) - for some reason the breaks are always cleaner, but old glass is always more difficult to work with than new - I also do neon sign work, and old glass is not good stuff to handle - new is easy to snap cleanly.
I would certainly "gas" the valve by breaking the nipple before attempting to decapitate it.
See: http://www.teralab.co.uk/Glass_Blowing/H..._Page1.htm
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