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.
Sugar coloring on a small scale is made in an iron kettle on an ordinary furnace. On a large scale an arrangement (oven) as represented by the annexed engraving is a practical device. The dimensions of the arrangement, size of kettles, depend on the actual requirements. A cast-iron kettle with convex bottom is set in bricks, so that only the bottom and not also the sides of the kettle are touched by the fire. The flue leads not along the sides, but directly outwards from the fire-place. The thickness of the kettle is from about one-quarter to three-quarters of an inch according to size. Too large kettles should not be used, rather a set of smaller ones where required, as the sugar melts and converts quicker in a small than in a large kettle. Above the kettle should be adjusted a conical roof, made of boards, somewhat larger in diameter than the kettle, and not too high above the latter, which should end in a sufficiently large pipe, leading into the flue to give way to the suffocating vapors arising from the converting sugar. The flue must have sufficient draught to pass the vapors immediately outside, else the eyes and throat of the operator will become inflamed, and working in the room made unbearable.
Fig. 427, - Sugar Color Kettle and Oven.
Fig. 428. - Sugar Color Spatula.
In the immediate neighborhood of this oven, but at least one foot higher, is another oven, frequently with an iron kettle on a cast-iron plate, for heating the required quantity of water. This oven or kettle is adjusted with an outlet and cock near the bottom, and by means of rubber tubing or an adjustable canal the required quantity of hot water is directed into coloring kettle the moment it is required. In establishments where a water heater or steam boiler is available this second oven may be superseded by a more practical steam-heating arrangement, etc. A necessary tool for making sugar-coloring is an iron stirrer or spatula with wooden handle, as represented by the preceding illustration.
In very large establishments, where steam-power is employed, the stirring is done by mechanical arrangement. An iron dipper is necessary to remove the coloring from the kettle to the sheet-iron funnel of the storage barrel or wherever desired; a discharge cock at the bottom of the kettle is not practicable, becoming too frequently clogged up by the sugar-mass; however, if the coloring is far diluted, a cock will be of great service, leading the coloring into a filter or clarifying apparatus, from where the liquid might be removed to the vacuum apparatus or evaporating pan.