This section is from the book "The Modern Cook: A Practical Guide to the Culinary Art in All Its Branches", by Charles Elme Francatelli. Also available from Amazon: The Modern Cook: A Practical Guide to the Culinary Art in All Its Branches.
To the stock produced from four calf's feet, add two pounds of loaf-sugar, the juice of six lemons and a dozen oranges, and the rind of eight oranges; put the stewpan on the fire to melt the stock, and then pour in the whipped whites of eggs, and continue whisking the jelly on the stove-fire until it begins to simmer; it must then be set down by the side of the stove-fire, covered with the stewpan lid, and allowed to continue simmering until the egg is set; the jelly must then be passed through the bag in the usual way, and just before putting it into the mould, a few drops of prepared cochineal should be added to give it an orange-pink tinge.
Note. - Lemon jelly is prepared in the same way as the above, substituting lemons for oranges.
To every pound of the finest loaf sugar, whatever quantity may be required, add rather more than a pint of spring-water; and when the sugar is dissolved, add half the white of an egg whipped up with a little water; whisk the whole well together, set the stewpan on the stove-fire, and as soon as the syrup begins to boil, set it down by the side of the fire to continue gently boiling, until it has thrown up all the scum; remove this as it rises to the surface, and then strain the syrup through a napkin into a basin, and keep it in a cool place for use.
First wash the isinglass in cold water, to free it from the dust that is apt to gather about it; then put it into a stewpan, and to every two ounces add half a pint of spring-water, and about one ounce of sugar; stir this on the stove-fire till it boils, then throw in the juice of half a lemon, and set the stewpan by the side of the stove, to continue gently boiling for about ten minutes, in order to dissolve the shreds of isinglass, and that it may thereby throw up all the scum, which should be removed as it rises to the surface ; the isinglass may then he strained through a napkin into a basin, and used for the required purpose.
Isinglass may also be clarified by adding a very small quantity of whipped white of egg, after it has been dissolved in water as directed above, and then allowed to cool previously to mixing in the white of egg; it must then be allowed to boil gently by the side of the stove-fire, and when perfectly cleared of all the scum, should be strained through a napkin.
Note. -There are several kinds of gelatine in use, which serve the same purpose as isinglass, with more or less success; all these may be clarified in the same way as the above.
Wash several sheets of white blotting-paper (of the best quality) in cold water; then boil them in two quarts, of water for about twenty minutes, strain the water from the paper, and pound it in a mortar until reduced to a fine pulp; mix this with a spoonful of washed white sand, then add both to the juice intended to be filtered, and throw the whole into a clean beaver jelly-bag. Pass the juice through the filtering bag until it drops as bright as spring-water.
 
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