1. Heat milk to 180 degrees to make sure nothing interferes with the delicious replicating bacteria. This could be done in a double boiler, but I didn't have anything that was going to work so I just used a big pot. I attached a thermometer to the side and stirred frequently. I didn't scorch the milk.
2. Cool the milk to 110 degrees. I filled the sink with cold water and set the pot in the sink. If we had room in our freezer for an ice cube tray, I would have added ice. I continued stirring to release the heat.
3. Add the started. I dumped in an 8 oz container of plain organic yogurt. I only needed 3 tablespoons, but I didn't want to keep an opened container of yogurt in the fridge. I guess I could have eaten it, but that thought didn't occur to me until just now.
4. Let the milk sit in a warm place. Some people use crock pots, heating pads or hot plates. My crock pot is too small and I don't have a heating pad or hot plate. I put my pot in the oven and turned the oven on very briefly every two hours.
I let it sit for nine hours and it produced a semi-tangy, not-to-thin and not-to-thick kind of yogurt. I really like the taste, but prefer thicker Greek style yogurt so I used a tea towel and a colander and strained the yogurt. If I would have more time, I would have strained it a bit longer, but I got out quite a bit of whey to be used for later projects. I mixed in some pureed strawberries and a little sugar to some of the yogurt. I also mixed in pureed apples and cinnamon to another batch. I made strawberry smoothies with some of the yogurt (honey, strawberries, yogurt and milk) and they were delicious. Making my own yogurt is definitely cost effective and I will most definitely do it again.