Manufacturer and builder 10, 1869
Water-Colors are finely divided pigments that have been mixed with a suitable binding material, so as to form a stiff dough that may be pressed into tablets. The pigments employed are either simply ground, or ground and washed. The binding material generally employed is either glue-water, or a mixture of this with a solution of gum arable or gum tragacanth. The requisite properties of a suitable material of this kind are that it should allow the tablets to be well pressed and prevent their cracking after drying. The grinding of the pigment and the mixing with the binding material are often accomplished at one operation, various machines being, employed for this purpose. Pigments of a crystalline nature, such as Paris and English greens, require a longer time for grinding that others. For ordinary water-colors, cheap and earthy pigments are selected, and less attention is bestowed upon their thorough reduction. However, it would be well if the poisonous colors should be rejected as much as possible, especially in those articles that are intended for children, who are apt to apply them to their mouths and expose themselves to the danger of being poisoned. There are no exterior signs whereby the quality of water-colors may be determined. Neither the silver and gold-colored characters, nor the dull appearance, nor a certain lustre, which is frequently imparted by a coat of colophony in alcohol, are any indications of superiority. This depends upon the quality of the pigment itself, as well as its state of division and the character of the cohesfre body employed. The draughtsman for whom these colors are mostly manufactured seldom requires more titan six colors, though the boxes generally contain more. Indeed, some authors assert that the three primary colors - red, blue, and yellow - are amply sufficient. In general, however, it will be found impossible to produce the required variety of tints by the use of only three colors.