This is a super easy way to make yogurt at home. And I mean super easy. There is no specific ratios of ingredients, or any specific ingredients other than listed in the supplies section.
Get yourself a cheapie cooler like this (most grocery stores have them.
Get one gallon of milk (whichever milk you choose will work) and some starter yogurt. The yogurt must be plain yogurt or you will taste funky fruit flavors!!!
Here is the optional metal grate. It is used to keep the glass jars off the bottom. This prevents milk from cooking on the bottom and cooking makes hard bits in your yogurt (yuck).
Fill your jars with milk. You will probably not have to use the entire gallon of milk unless you want to.
Place your milk jars in a canning pot or equivalent if you are making a smaller batch. Fill with warm faucet water and begin to heat. You may have to experiment with gas/electric stoves.
Heat to 120 degrees Fahrenheit (~49C). Hold for at least 10 minutes, I generally go 15-20 minutes to sterilize the jars and milk.
After sterilizing, wait for your milk to cool to about 100/110 F (~38C). Quickly inoculate your warm milk and seal it back up to keep it warm. Stir the starter yogurt in well with the warm milk.
One spoonful of yogurt per container should be plenty, but if you want to be sure, put in two or three :-)
Put the lids back on quickly!
Pour the hot water from the canning pot into the cooler. Place the jars of yogurt and milk mix into your cooler. Close the cover quickly! Yogurt bacteria like it a steamy warm: 90-100F ~(38C)!
Seal in the goodness and put it out of the way.
I cover the whole thing with towels to keep it warm.
Let your yogurt sit undisturbed for 10-12 hours or longer. The longer it sits, the more thick (and sour) it will be. You can then put your new yogurt in the refrigerator or move on to optional steps.
The following are optional steps. I like Greek style thick yogurt, so I drain the whey from my new yogurt before I put it in the refrigerator. You can also add flavors in the next steps if you prefer.
Prepare your strainer, cheesecloth and a bowl to catch the whey.
Place the strainer in the glass bowl. Pour your yogurt in and let it sit for a number of minutes. The whey will be collected in the bottom bowl.
Pour your yogurt into a container after its done draining. Another pair of hands is helpful ;-)
I like to add a little honey. One or two tablespoons is sufficient for most large yogurt containers. Stir well, refrigerate and enjoy!!