Still poking away, but I'll be out of town a lot soon for work, so we'll see how this goes. Used some silicone caulk to make a seal a couple weeks ago, and stuck an empty jam jar over it just to see what would happen. Also made a crude crookes radiometer to get a rough idea how close I was getting to the needed roughing vacuum.

I never got my radiometer to spin, even in direct sunlight, though I couldn't tell for sure whether the issue was with the vacuum or the radiometer itself. That's the problem with trying to get two experiments working at the same time.

Anyway, I left out alone for a while to think, and came back to it about a week later. To my dismay, the vacuum had managed to pull a bunch of oil out of the vacuum pump and collected out in the jar. This was going to be a royal pain to clean up now. Oops...

Then I noticed the bubbles, streaming in from all around the edges. The issue is at least with my silicone seal! Ah, interesting. The good news is this means there's still a chance my cheap pump might work. Here's a link to video of you really want to see the bubbles.

https://goo.gl/photos/xtBzxkbGbeoLadc76

Back to the drawing board...