How to make yoghurt: First, all dishes must be clean--we don't want to grow anything unwanted. Even if you are using pasturized milk, first heat it up to 85 degrees celcius--almost boiling--just to make sure everything is dead. Next, let it cool to 50 degrees celcius--this it the temperature to culture the yoghurt. Add 1 tablespoon of plain yoghurt for every 4 cups of milk. It has to sit, preferable at 50 degrees, for 4 to 10 hours, depending on how strong you like the taste. I put it in a small cooler--the kind that fits a 6 pack--and leave it over night. In the cooler I can make 12 cups easily at one time. Just remember to save some starter for your next batch. After a month or so, you will need to start with a new starter. I would avoid using plastic wrap on anything hot--once read an awful article about how the chemicals start to come out of the plastic in heat.