Very interesting information.

As always from our Max

I love those super old spherical tubes, it is just crazy to me how much manual effort went into these! Is that an E12 base?

Manual labor was much cheaper back then, Drew. I don't know the exact cap size of this lamp... I would say it's closer to E14.

Ria & Sammi - Thank you ladies, glad you are enjoying this presentation. That museum is a very interesting place and more pictures will come (as you can guess from the counter in the title)

Been planning to have a go at making a triode for fun just need to get the vacuum pump and glass seals a little better first. Glad to see there's still a museum in Eindhoven, shame its not in the Evoluon.

The Evoluon was sold off to developers in 2018 and the only museum in Eindhoven which is still owned by Philips (i.e., the original company factory from 1891 located at the Emmasingel in the city center) is mostly about marketing stuff. The really interesting place to visit, the Philips Historische Producten museum, is actually run by volunteers (mostly former Philips employees). This shows the difference in management of the company's history between corporate suits and real enthusiasts.

Good idea about the homemade triode! That's something I should try as well, the De Forest's Audion design is quite simple (I need to get my hand on a spot welder though). As for the vacuum issue, one possibility is to seal the tube off with a significant fill pressure enabling a glow discharge between electrodes (preferably the grid and the plate). If the gas fill is of molecular nature (e.g. air), then plasma dissociation and gas clean up will result in a significant pressure reduction that will eventually result in the extinction of the discharge.

I have done a decent amount of research into homemade tubes, and I believe that a small titanium getter filament that can be powered on demand to clean up gas would be very effective for this purpose. Obviously it wouldn't look genuine because there's an extra filament that isn't normally in the envelope, but if I am thinking correctly the only gas the titanium can't fully "get" from the air is argon, which there isn't a whole lot of in air (even less if you purge with pure nitrogen/co2/whatever before vacuuming). I have some reason to believe that with just a two stage rotary vane pump getting you down to ~10^-3 torr, a titanium filament may get you all the way down to the ~10^-7 torr range (more than suitable vacuum)! Though this is unconfirmed and obviously depends on your cleanliness while assembling among other things i'm sure. Making it into a ring shape is of course another option if you have an induction heater, though I think evaporating it will be a problem (it probably will slump before evaporating). All things on my bucket list to try

The use of a metallic getter is also an option, but it will require a more complex lamp design. I don't think we need to go as low as the 10^-7 torr range to make this work, the original Audion tube did not operate under high vacuum.