This section is from the book "Three Meals A Day", by Maud C. Cooke. Also available from Amazon: Three Meals a Day.
A tablespoonful of burnt sugar dissolved in a little water will make a clear soup the color of brandy or very strong tea. To make this caramel for coloring, burn in a dry saucepan over the fire, stirring constantly until scorched.
This may be obtained by enriching the soup-stock with a piece of veal or veal bones roasted brown, and using browned flour for thickening. This will give a rich color. The flour may be browned in a dry saucepan over the fire, stirring quickly until a deep shade is obtained.
Bruised spinach, the green leaves of celery, or pounded green peas will give a green color to soup.
Ripe tomatoes; or, lobster coral, will color soup red.
Cream may be added, use white vegetables with rice or pearl barley. A teaspoonful of corn starch for thickening does not injure the clearness.
Soup may be still farther clarified by removing fat from stock and boiling slowly with the whites of one or two eggs, according to the quantity of broth. The egg and the sediment will rise and may be carefully skimmed from the top.
 
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