Pour the raw milk into a clean glass mason jar leaving about 1 inch at the top. You can use cold milk right out of the refrigerator if this is more convenient. Gently stir in live kefir grains. Roughly one-quarter cup of grains is sufficient to ferment the entire quart.

Screw on the lid and leave on the counter at room temperature for 24 hours. Over this time, you will see the milk slightly separate and thicken.

The kefir should be ready after 24 hours of fermentation time. If powder culture was used, you can use the kefir as is. If live kefir grains were used, gently strain them out to use again with the next batch of raw kefir.