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.
We have already mentioned under the foregoing heading that, in the course of converting the sugar or glucose into caramel, most invariably small quantities of sugar and chemical admixtures are charred which are not removed by the usual subsequent filtration through coarse flannel, but being so minutely divided, remain in the concentrated coloring, and if left therein would separate and cause sediment when the color becomes diluted, as in the beverage. To guard against this dilution of the coloring, filtration through a more effective felt bag and evaporation to proper consistency in a vacuum ap-' paratus or over a water bath is already recommended. However, clarification is considerably aided by a fair dilution of the color, mixing it with powdered pumice, glass sand, asbestos, etc., and running it through a good filtering bag or one of the many clarifying apparatus we have described and illustrated for the clarification of syrups and other liquids in former chapters, to which we refer. Commercial sugar color frequently needs this treatment.