Hi all I was wondering if any of the Vapalux experts / obsessives in the house could help me with a lamp debate. On the older vapalux glasses with the hole, was this hole drilled or formed with the glass in some way? I have a 12.2ish cm tall pyrex marked holed glass which seems genuine based on the reference gallery and to me the hole is clearly drilled, it has tiny chips etc all round the edge. On the other hand I have just spoken with a chap who has a 12+cm tall glass with a hole where the hole looks to have been formed with the glass, the hole is smooth and formed looking as though it was cast in place or maybe melted through. If its a taller glass which suggests to me its not a modern glass drilled with a diamond core drill or similar, so did they swap methods halfway through? Any thoughts would be appreciated...
I can’t speak specifically about Vapalux, but others might. A hole drilled in glass can be left as is, or the drilled hole can then heated directly to produce a smooth edge. I’ve done both. I don’t know if there is another method for making holes in glass (direct flame? hot poker? mould?). Tony
Speaking to a trader in these items, I’ve been informed that holes in globes and chimneys can be (are usually?) formed with heat and a hot spacing rod. The problem of making holes in glass is that longevity (glass does not crack in use) is best achieved by ensuring the glass is annealed properly with or after the formation of the hole. Cheers Tony
Thanks Tony, good to know, i have definitely seen some petromax type glasses which look like a hot rod was used to poke a hole, never knew W&B did it too. Interesting, so it looks like they may have done both at different times. Its that or W&B also made tall glasses with no hole that people then drilled or rodded themselves, which makes no sense since a tall glass without a hole is a pain to fill, you'd have to take the whole hood off every time. I suppose the other possibility is that someone flame polished a drilled hole to make it look neater, which I get since the drilled ones look a bit DIY at the best of times, 1940s drilling tech being what it was.
@Nevermindthedarkness The 'typical' Petromax type glass is a plain and straight cylinder without any hole. You might have the holed glass for the austrian Ditmar and Phoebus lamps in mind. These holes are hot formed with a relatively thick (molten) bead of glass on the circumference. Any such thickness is absent with any drilled hole, as on W&B glass. Afaik W&B never had glass with holes that were hot-formed, and I think you misinterpreted Tony who does not say so.
My guess is that the hole was ground-out or maybe scored and broken-out. Might result in less breakages than drilling. What type of drill would be suited to a curved glass?
Ian You can drill curved glass (with a reasonable chance of breakage) using a circular diamond encrusted drill piece:
I have no idea which method was used to hole glass globes by the german Schott company, but they are not drilled, ground or cut as far as I know. Mechanical holing simply induces strain on the glass that might not like it on too many occasions. I think there is consensus on why W&B changed from a drilled holed glass to a shorter glass without a hole: too expensive due to too many failures to produce.
Interesting, if W&B never hot rod bored their glasses then I guess this is either a glass from another lamp entirely or someone decided to tidy things up a bit. Many thanks for the thoughts all, if anything else develops or i can get a photo I will let you know...
