- Pour milk into stainless steel pot.
- Heat pot over low heat to 100 F, whisking occasionally.
- Now pay close attention and turn down the heat a bit, when the temperature gets close to 110
- Go ahead and whisk in the old yogurt (make sure to break apart any clumps). I use five tablespoons per half a gallon.
- When the temperature gets barely to 110 F take the pot off the heat and immediately pour into the glass jar and close tightly with lid.
- Wrap the jar in whatever combination of insulating materials is available. Coolers, clothing, blankets, and sleeping bags all work well.
- Wait a minimum of 8-12 hours. Take the jar out (hopefully still warm) and put it in the fridge to sit for several hours.
- We suggest placing jars of hot water inside a cooler, alongside the container of yogurt.