This section is from the book "The Flowing Bowl - When And What To Drink", by William Schmidt. Also available from Amazon: The Flowing Bowl: When And What To Drink.
This, for every Russian household, necessary national beverage, which is also used for different soups and other dishes, is manufactured for the family use in the following way:
Ten pounds of rye flour, one pound of malt, and one pound of buckwheat flour are stirred in a tub with three quarts of warm water; then pour over it three quarts of boiling water; after half an hour add again six quarts of boiling water, and repeat this in half-hourly intervals three times more; stir the flour in the water well; let it get cool, cover, and let it stand in a rather warm place; the following day you thin the kvass with cold water; put it in a cool place; let it thoroughly sour, and bottle. When the kvass is nearly used up, leave a couple of quarts of the beverage in the tub for the next souring; the thick sediment at the bottom is then thrown away, but it may be used on farms successfully as food for the beasts of burden.
Another recipe is the following:
Twenty pounds of rye flour, and as much malt flour are stirred with cold water, and kneaded well; then form loaves of bread from ten to twelve pounds each; press with the fingers some deep holes into them; pour cold water into these holes; place the loaves in a very hot baking-oven, and bake them brownish black; leave them over night in the oven; break forty pounds to moderate-sized pieces; put them in a tub; pour fifty to sixty quarts of boiling water over them; cover the pot with canton flannel and a wooden lid very well, and let soak for two hours. Pour the entire quantity into a cask, the bottom of which is covered with cross-laid slats, which again are covered by straw to prevent the falling through of the bread; through a side-faucet decant the kvass, and fill it again into the cask; repeat this a few times to clear it sufficiently; in a vessel already soured it need stay for only twenty-four hours, but in a new cask it must stand for a few days until it is sufficiently sour.
Besides this bread-kvass, this beverage may be made also from fruits: so you may make apple-kvass by rowing apple-slices and whole pears on strings, and drying them in the sun; in a cask of about fifteen gallons you put twenty-four quarts of dried apples, and as many dried pears, and fill the cask with boiled but cooled-off water; let it stand for three days on a rather warm place; then bring it into the cellar; cover the bung-hole with canvas, and let the kvass ferment. After fermentation bung the cask; bottle after four weeks; add to each bottle a handful of raisins; cork, and seal, and let them lie a few months in a cellar; cover them with a layer of sand.
 
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