nothacking
Homemade glow lamp: it's borosilicate glass melted with a oxy-propane torch. The outer diameter is 11mm.

The vacuum from my rotary vane pump isn't perfect, and there's a lot of residual air left over (that's what's glowing), but it should still be good enough for a triode or small CRT.

... although I haven't figured out a good way to do glass-to-metal seals yet. This one has copper plated steel wire (CTE=~10 um/[m*K]) passing through borosilicate glass (CTE=~3 um/[m*K]), which aren't close enough to stop thermal expansion from breaking the bond: The tube only worked for a few hours.

Might have to buy some tungsten wire (CTE=~4 um/[m*K]) or figure out a graded seal: soda lime glass bonds to the wire quite well, but it's is very annoying to work with.
Jun 6 at 9:56pmWeb
Show threadnothackingJun 7
Ok, so I was able to borrow some tungsten wire, but it's like 50 microns thick. It seals nicely, but it turns out that invisible wire = invisible shorts.

I'll either have to figure out a way to handle it or buy something thicker.
Show threadnothackingJun 7
A fun thing about tungsten is that even though the torch isn't anywhere near it's melting point, it will burn through in under a second.

Invisible and flammable wire -> Nothing left after making the tube

... and that's probobly enough exotic metal fumes for a day. I don't want to invent any new diseases.
Show threadnothacking6d ago
Ok, found a neat way to leak test a tube whith out sealing it: Pump it down, use high-voltage AC (like tesla coil) to ionize the residual gas and spray "canned air" on suspect areas.

Even a small amount of the fluorinated refrigerant will quench the glow discharge and change the color.

... just don't do it near the torch: burning the gas produces some rather nasty fumes.
Show threadnothacking6d ago
First successful (non-leaking) glow tube: The lead ins are 10 um tungsten wire through borosilicate glass. Tube is full of low pressure air.

Neon sign style with the electrodes on opposite sides... which pushed the operating voltage above what my DC power supply can do. The photo shows it running on AC (hence the glow in the evacuation stem)