The directions are really detailed (especially if you click-thru to the more thorough version here), so I felt pretty confident. Worst-case scenario, I was out a few bucks for the milk and yogurt cup (starter), and would have a damaged ego; best-case scenario I could feel really cool (and save $$, be healthy, cut down on production of plastic yogurt cups, etc... but mostly just feel cool)!
I borrowed a candy thermometer from a friend/co-worker, since I wanted to be sure I was doing it right. The whole process took me about 8 hours, though most of that was just letting it "incubate" and didn't require much work. I did discover that my cooler probably isn't the most insulated one ever and when I went to take the yogurt out the temp had dropped, so I added some more boiling water and let it sit for another 1-2 hours instead. Here are some pics I took:
We had some of it for dessert tonight (yeah, I know... it's generally strange for Americans to eat non-frozen yogurt for dessert, but it's normal in Spain and now I'm used to it!) with a little sugar and honey - natural/plain yogurt all by itself is kinda icky if you ask me. It was pretty good, though if I do it again, I think I'll try to let it incubate longer (and add the extra boiling water sooner to keep the temp up) as it was a bit runnier than I'm used to, and I can only assume it's due to an incubation faux pas.
Overall, I'm just glad I have an edible result and didn't have to dump it out completely. I got some free Post Trail Mix Crunch a while back, and I'm thinking this yogurt will probably be a great substitute for milk with that, since the cereal has a granola-y texture.
Making yogurt, Soli Deo Gloria...