This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
The principal secret of the sugar-coloring manufacturers is that they use neither refined nor other cane or beet-sugar at all, although their coloring is said to be made of such, and bears a term that should signify such a descendence; they use simply glucose, grape or starch-sugar, which is considerably cheaper than cane or beet-sugar. Sugar coloring or caramel may just as well be prepared from inferior qualities of sugar, from molasses, or glucose, and an equal product obtained as that prepared from "refined sugar". When sugar or its substitutes are heated to between 180° and 200° C. (356° and 392° F.), sugar turns brown, evolves a peculiar, suffocating vapor consisting of carbonic acid, carbon oxyde, aceton, acetic acid, etc., and is converted into caramel, C13 H18 09, parting at the same time with two equivalents of water. A former secret of the manufacturers also was to add small quantities of alkalies (soda or potash) to hasten the conversion, and to leave out any admixture when the coloring is used for coloring vinegar, as in the latter case the coloring with the alkalies would cause turbidity.
An addition of some carbonate of ammonium is now generally made to all kinds of colorings (whether intended for carbonated beverages, wine, beer, rum or vinegar), which is again volatilized by the heat, and is of service for hastening the conversion, increasing the intensity of the color, and neutralizing small quantities of huminic acid, that are invariably formed at the end of the operations, thus preventing cloudiness of the sugar color; however, for other than vinegar colors, carbonate of soda or potash may be used if desired to the same effect. The proportions are as follows: One pound of soda or potash, or one and one-half pounds of carbonate of ammonium, to every thirty pounds of sugar or glucose.
Sugar coloring is a harmless preparation, and, as far as carbonated beverages are concerned, a preparation innocent of any deleterious or deceptive attributes. Where much sugar coloring is used, as in sarsapa-rilla, root, etc., beers, no gum foam is necessary, as the sugar coloring itself has a great deal to do with the foaming of a beverage, and produces a very persistent head.