Adding kefir grains to milk or adding pre-made kefir to milk are two methods for making kefir. The second method is somewhat precarious, as the results depend on the quality of the pre-made kefir.
To make kefir using kefir grains, add 1 tablespoon of kefir grains and a quart of milk to a large glass jar. Cover the jar with cheesecloth, and secure the cheesecloth with a rubber band placed around the lip of the jar. Allow the kefir grains and the milk to rest at room temperature for 12 to 24 hours. The kefir is ready when the grains begin to coagulate at the top of the jar. Kefir's texture should be similar to loose yogurt.
For a smaller amount, add 1 teaspoon of kefir grains and 1 cup of milk to a pint-sized glass jar. Cover the jar with cheesecloth, and secure with a rubber band.
Strain the kefir through a plastic sieve or colander. For best results, avoid ultra-high pasteurized milk, which potentially prohibits the growth of cultures. Whole-fat animal milks tend to respond best to the culturing effects of kefir grains. Examples of these milks are cow's milk and goat's milk, including raw, pasteurized and reconstituted milk.
Two percent and reduced-fat milk are also viable choices for making kefir, but the kefir grains may require slightly longer to fully culture these low-fat fluids.
To make kefir using pre-made kefir, combine 1 tablespoon of kefir per 1 cup of milk. Mix the concoction well, cover it, and let it rest at room temperature for 12 to 24 hours.