This is my first attempt at making yogurt without the aid of an electric incubator. In the past I have used an inverted Rubbermaid container, on top of a heating pad. That method produced a good tasting yogurt but was more labor intensive (filling lots of small containers) and required a space to set up the heating pad incubator. I read about using a cooler filled with hot water, instead, so decided to give it a try. First I assembled everything I'd need. 3 clean quart canning jars, with lids and a candy thermometer; the cooler (mine is a bit larger than needed); Milk, yogurt, a pot and a spoon. You'll also need a measuring cup and a measuring tablespoon.
Now we're ready to begin. You can make as a big a batch as you'd like. For every pint of milk you'll need 1 Tbs. of plain yogurt to use as a starter. Measure out your starter and place in a bowl, on your counter, so it can warm up while you're preparing your milk.
Next put your milk into a pan and heat it over high heat, stirring constantly. You want to heat it to between 180 and 185 degrees in order to sterilize your milk. A candy thermometer comes in very handy.
Once you reach the correct temperature, remove the pan from the heat and stir and cool until the milk is below 120 degrees (but don't let it get below 90 degrees). To speed the cooling I like to place the pan in a sink holding cold water.
The above is the standard way to make yogurt. Usually at this point you would place your yogurt into an electric yogurt incubator of some kind. But what if you don't have electricity? Can you still make yogurt? Yes. All you need is an insulated container large enough to hold your jars and some hot water. Here I have divided my yogurt between the 3 clean mason jars.
And now into the cooler they go, along with enough hot water (I used hot tap water) to fill the cooler to just below the lids of the jars.
I then placed the top on the cooler and waited. I did drain and refill the water a couple of times during the 24 hours. And this morning I was rewarded with some finished yogurt.