How to glue valve glass to base

Hello,
First time on the new board. Thanks to the new hosts for providing this forum.

I bone-headedly pulled an old (early 60's) 5Z3 rectifier by the glass and the glass is loose from the base now. The tube still functions fine, but I'm wondering if it wouldn't be better to re-glue it, and if so using what? Epoxy? In the states here we use polyurethane expanding glue a great deal (Gorilla Glue), but I'm not sure if it's heat proof. Any thoughts?

Mark

[Richard]

Hi Mark

If it's a valued valve I'd glue it as it will only be held by the wires at the moment.

Only retail stuff I've found is available over there I believe; JB Weld from auto stores. This is rated to constant 300°C (yes 572°F = x3 boiling water) which is higher than the glass envelope is rated. Epoxy, easy to use.

Rich

[Paul Barker]

There is a trick to geting it right, if you just use a glue which doesn't allow for expansion and contracxtion of the envelope the glass cracks.

I don't know what the trick is, but I do know there is one.

[Basil]

You will need to be very careful if using epoxy glues, the problem is not during use but during the curing stage. The heat generated can fracture the glass at the base line, I've seen old PM24 output valves destroyed this way.

For vintage radio valves I just put a thin line of superglue round the edge of the base where it meets the glass and have had no failures albeit to mainly 1930s valves. Another method I have used is to wind vulcanising tape round the area between the base and glass, similar to a method employed by the War Department in the 50s, take a look at any MoD Boxes marked
"Servicable" on CV Type octal base triodes.

Basil

[steve s]

I was once told to fill the space with her best clear nail varnish...
and leave overnight to set

never tried it but i know a man who has...

cheers steve

[Greg.]

Hi Mark,

I've also used Super (Cyanoacrylate) Glue as Basil describes to very good effect. Doesn't seem to be effected by heat and doesn't fracture the glass. It's also very easy to drizzle in to make the joint secure without leaving a visible glue line.

Best wishes,

Greg

Thanks to all. I'll let you know how it turns out.
Mark

[Richard]

From,

http://antiquerestorers.com/Articles/jeff/shellac.htm

Electrical – shellac mixed with marble dust is used by lamp manufacturers to glue the metal base to glass incandescent bulbs.

Rich

[Cyprus Martin]

I've used the shellac/marble dust for a long time, not that I've had many valve bases come adrift but over the years there have been a few. It was a guy at an army surplus store told me about it when I bought an old R1156 set to convert to short wave.
Martin