It actually worked! This video was taken at the end when we finally got it working, which means I had spent the last three hours inhaling IPA and CO2 fumes, so pretty much ignore everything I say about which particles you're seeing; I'm wrong. Just read the Wikipedia article for it.
Starting at the beginning, Jeff and I had no idea what we were doing. I read a few vague articles on the principle of operation, but we had no real solid plans or expectation for it to work.
Erlenmeyer flask from his chemistry days at Berkeley, which was perfect for this project. Different articles said different things about which alcohols you can or can't use, but we found a 16oz bottle of 99% Isopropyl alcohol at Safeway, and that worked for us. We also bought 6lbs of dry ice at Safeway at $1.49/lb, which was pretty easy (just ask for a brick of ice at a register and show ID).
We decided to try and have a heated alcohol reservoir like they had in the Exploratorium instead of just soaked rags or paper, so we went to Halted and picked up some power resistors and a sample vial. We didn't see much difference between this and just a hand-warmed rag, so I wouldn't recommend bothering with this unless you want to run it for a long time like for a science fair.
baling wire (family go-to tool, even two generations after moving from Montana).
Once the alcohol source was taken care of, the next step is to cool the bottom of the flask to cause it to condense again. Our first attempt was by adding crushed dry ice into the flask, but this didn't work, causing a ton of turbulence by the subliming ice.
This is wrong; don't put the dry ice in the container.
This also didn't allow us to use the black paper on the bottom of the flask, so we tried again instead placing the dry ice in a pie pan around the flask. This removed the turbulence problem, and we started seeing falling droplets in the flask.
So the tricks here are:
- Keep the dry ice out of the container and finely powdered to better cool the container (unless you manage to get a flat piece, you lucky dog you)
- You can use drug store IPA, and don't need anything more than your hand to warm it.
- Lay a piece of black paper on the bottom of the flask to see the white droplets against
- Have a pool of alcohol on the bottom to help form the saturated region
Of course, once we had had enough electron spotting, we had to do something with the rest of the dry ice.
This may or may not have ended up with me managing to freeze a pie pan to the garage floor for several hours before the rest of the dry ice sublimed away...