At the beginning of the year I bought a yogurt maker at a thrift store; since then, I've made batches of yogurt on a regular basis. It's amazing what milk, powdered milk, starter yogurt and hours of waiting time can produce.
Each batch of yogurt takes a half gallon of milk, a cup of dry milk powder (which adds extra nutrients and a bit of firmness) and a half cup of live-culture yogurt. After filling the maker's five containers, there's about a half cup of liquid left over. Usually I end up drinking the leftovers, although I don't care for warm milk. Today, since the outside temperature is supposed to get to almost 100° (with a heat index of 107°), I decided to put the extra milk outside to see if it would culture, too.
I poured the leftovers into a pint-sized jar, wrapped the jar in a dishtowel and set in in the sun on the black wrought iron table on the deck. After a couple of hours the deck, which faces east, lost the sun, so I moved the wrapped jar to the west-facing front porch. On the walk through the house I opened the jar and tasted the milk. It was ALMOST cultured!
When it was time to start dinner I retrieved the jar from the front porch. I took the lid off the wannabe yogurt; it smelled good, but was curdled. (I guess it had gotten too hot in the sun.) It still tasted OK, though, so I added it to the can of cream of chicken soup that was the base for the turkey and vegetable casserole I was making. Served over brown rice, the whole thing was quite tasty.
My experimental container may not have turned out too well, but in the meantime the other containers are gradually fermenting. I'll be able to put them in the refrigerator when I go to bed tonight, and they'll be waiting for me for breakfast tomorrow.