This section is from the book "The Manufacture Of Liquors, Wines, And Cordials, Without The Aid Of Distillation", by Pierre Lacour. Also available from Amazon: Manufacture of Liquors, Wines, and Cordials, Without the Aid of Distillation.
No fluid can be successfully colored that is not perfectly clear and colorless of itself; and when it is charged with coloring matter, the fluid will always retain its transparency. The first step then towards coloring these beverages, will be to clarify the water while it is boiling, with the articles that are usually added ; to every three gallons of water add one egg, whisked to a froth.
The coloring substances, which are most commonly used, are red, yellow, and brown. The red is obtained by infusing bruised cochineal, sanders wood, or logwood; the yellow from gamboge, or saffron, and the brown from burned sugar, and a purple from turnsole. The necessary coloring substance should be added to the water while it is boiling, and should remain in the liquor until it has yielded the necessary quantity of coloring, or the coloring substances can be digested in proof spirit, and added to the liquor until the re quired shade has been produced.
Molasses and brown sugar should not be used in the formation of liquors that are to be colored. Effervescing liquors that have a dull, heavy appearance, after being colored, will be rendered quite transparent by passing them through a filter, composed of alternate layers of charcoal and sand.