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How to make kvass
Put 1.5 liters of water into a pot and bring it to a boil.
For this recipe you will need 1.5 liters (0.4 us gal) of water. You can make more or less at a time, but make sure to scale ingredients properly.
Take 2 slices of rye or pumpernickel bread. Toast them in a toaster on maximum settings.