It is time to make your own yogurt. It is easy and about half the price.
Start with 1/2 Gallon of whole milk. Bring it to 180 degrees F (Hot, but not boiling). Let the milk cool back down to 110 to 115 degrees.(You know, the temperature you would feed the baby.) Scoop up a 1/2 to a cup of regular unflavoured yogurt and add it to the warm milk. (Make sure it is a live active culture. Most yogurt is, but some thicken the milk with stabilizers.)This is the live culture that will ultimately make the milk thicken into a solid. This mixes easier if you mix it with some of the milk first before pouring it back into the pot. Stir to combine.
The mill is now ready to put into clean jars to allow to thicken. The trick is to keep the milk warm for an extended period of time. I usually put them into a pot of warm water about 3/4 up the jars, cover with the lid and wrap a towel around the pot, but you might have to put fresh hot water in periodically as the process takes several hours to work.
In the old days the jars were placed on the wood stove where they could keep warm. You also can use an insulated cooler surrounded by warm water. Depending on your environment temperature, culture strength this can take 12 to 24 hours.
If you have a crock pot you can cut the time down to 4 to 6 hours. Place the jars in warm water and press the warm button. If you do it the old fashion way like I do expect that you might have to leave it over night.
If you have used live culture and it is still runny it will solidify by reheating the water. Be careful that you don’t get the water too hot as it will kill the culture. Just make sure it remains “baby bottle” warm.
If you want thicker yogurt place your yogurt in a strainer lined with several layers of cheesecloth and let the whey drain into a bowl until it reached a consistency for your taste. Be sure to save the whey as it is full of vitamins and minerals. You can use it in smoothies, added to soups or in bread or pancakes. I like to just drink it.