The character on the mug below is Tooticky, a Moomin character who can make anything. Tove Jansson modelled her on her own lover, Tuulikki Pietilä. (She reminds me of bink.)
The grocery store's yogurt section is 4 feet long and 4 shelves high, but the other day I had to search hard to find a *plain* unsweetened yogurt---the rest were all mango fluff flambé, chemically sweetened and carrageenen thickened. All natural flavors removed!
So I decided to make my own, something I haven't done in years. I didn't bother to look up the recipe--I just
1. heated 2 percent milk [see boldfaced note below]
2. put it in a ceramic bowl
3. stirred in a couple big spoonfuls of live-culture, plain yogurt
4. covered it, and stuck it in the oven overnight, where the pilot light kept it warm *
It turned into a wonderful thick liquid, the consistency of kefir.
According to this online recipe, homemade yogurt is often runnier than commercial--you can add powdered milk at the start to help it set up.
Also, I should have heated the milk to the boiling point, then let it cool until warm to the touch (about 118°F- 110°F).
Otherwise, it's that simple.
You don't need thermometers and special tools. Like bread and babies, yogurt's one of those basics people have been making forever. The living beasties that get the party started (yeast, sperm, Lactobacillus bulgaricus) are pretty tough.
* My favorite yogurt-making tip was to put the fermenting batch in your car on a warm day, to stay warm. Just don't knock it over!