Pour the entire carton of milk into a large pot. Heat to 180 degrees (F) over medium-high heat stirring occasionally. Once you’ve achieved that temperature, remove the milk from the heat and allow to cool for about half an hour, depending on your household temperature. (I set my kitchen timer in ten minute increments otherwise I will forget about it)
*Once you have created your first batch of yogurt, you can use it instead of the store bought yogurt to make your next batch.
Once the ingredients are combined, you'll need to keep the jars warm overnight. For this, I use a great quality cooler. This is where you could also use a dehydrator or a slow cooker. Once thickened, store this yogurt in the refrigerator for up to a week.
A note about raw yogurt:
The reason we heat the liquid to 180 degrees and then allow it to cool is to kill off any bad bacteria (before adding the good bacteria). Proponents of raw dairy products skip this step, heating the milk to only 110 degrees which gives it the warmth it needs to ferment properly.