1/2 Gallon Milk                                                              1 single serving plain yogurt from the store.   Warm up the milk to about 96.8 F - hand warm.Take either 1 big Tupperware container or several smaller jars, with a lid. Fill the container 1/2 way with the warm milk. For the big container, add 1single serving plain yogurt and stir until the yogurt has dissolved. For the smaller jars ( like a marmalade glass or pickling glass) add 2 teaspoon of plain yogurt and stir. Fill up the container to the top with warm milk and close the lid. Keep it warm for at least 8 hours. To keep it warm I use an old cooler. I wrap the container with the milk in a large blanket. In order to keep the temperature steady, I fill up a hot water bottle with very hotwater and place it under the container. I close the cooler and let it sit for 8 hours.