Pictured above are the items you will need to make yogurt, Powdered Milk, Water, 1/4 cup of yogurt with live cultures, a thermometer, whisk, pan, and incubator. In a large pan add 1 and 1/3 cups of non-fat dry milk with 3 and 3/4 cups of water, whisk well, let sit, then whisk again. Heat the pan of milk on low until it reaches a temperature of 180, remove from heat and allow to cool to 115. When the milk has cooled to 115, add the 1/4 cup of yogurt and stir until blended.
Pour the milk/yogurt blend into the incubator (ours is a rubbermaid water cooler).
Put the lid on and let the yogurt sit overnight.
The following morning pour the thickened yogurt into a storage container and refrigerate. This recipe makes approximately 1 quart of plain yogurt.
This is an easy peasy way to make yogurt, I have always had success with this method, just make sure that you have plain yogurt with live cultures to start with, and that you do heat the milk to 180 and then make sure that it cools to 115. To make more, simply use a 1/4 cup of the yogurt you just made to get the next batch going!
Not only is this an easy recipe, it does not take any expensive equipment and it uses no energy while it incubates. I made a double batch in a larger water cooler, and I would assume that you could make large amounts in a regular cooler. The key is to have a container that is well insulated so the mixture stays warm long enough to thicken.