This section is from the book "The Epicurean", by Charles Ranhofer. Also available from Amazon: The Epicurean, a Complete Treatise of Analytical and Practical Studies on the Culinary Art.
Clarifying is not only for the purpose of rendering wines clear, but also to free them of any dissoluble matter which might precipitate later.
To clarify a cask of wine containing two hundred and twenty-five quarts, beat up partly five egg-whites with half a bottleful of wine; take out eight quarts of wine from the cask, pour in the clarifying matter and insert a stick split in four; move this about in every direction for two minutes so as to mix in the whites well, then refill the cask with the eight quarts previously extracted, and finish filling with wine or water; put back the bung. Five or six days after the wine should be clear, but in case it is not sufficiently so draw all the wine off into another very clean cask and reclarify once more the same as before, leaving it five or si>: days: it can then be drawn.
White wines are clarified with fish isinglass. Beat with a hammer a quarter of an ounce of the isinglass, tear it to pieces, cutting it apart with a pair of scissors, then soak it for eight hours in sufficient wine to cover; when swollen, and it has absorbed all the liquid, pour over as much as before and leave it for twenty-four hours; then add half a pint of hot water; stir this about to crush, then press forcibly through a towel. Beat it with a whip, pouring a little white wine slowly over until the entire solution makes one quart of liquid. Before pouring it into the cask beat it up with three pints of white wine and finish the same as the red. The egg-whites or isinglass can be replaced by prepared powders.
 
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