Back in February, I wrote about the Zeer pot refrigerator. I found a video to add to that post, and finally got around to making my own Zeer pot today. I used 8" and 12" brown unglazed clay pots, and got a ripped bag of "play sand" for only $1.50. The sand says it has been washed and screened, so it seemed safe to use for this purpose. The sand was very warm from sitting out in the sun at Lowe's, so the starting temp in the inner pot was 86F. I added 6 cups of tap water to the sand, and covered the pots with a thin wet towel. I also set a small fan blowing on it, since the pot is on a kitchen counter and a breeze is helpful with the evaporation process.
The humidity today is 86%; these are supposed to work much better in a dry climate. That said, after 4 hours, the inner pot temperature is 69F and the ambient temp in my kitchen is 80F. I'll turn the fan off before I go to bed tonight, and see how things look in the morning.
I also got a matching 8" saucer to use for a lid on the inner pot. I don't know if I need it yet, but it seemed like a good idea to help keep bugs and dogs out of it :) I'll post any updates in the comments here.