2 Of the vehicles for the Colours used either for Painting, or forming Grounds, for Paper Hangings.

THE VEHICLES for the colours, as before observed, are such as are either formed of water or varnish. When water is used, it must be inspissated with size and gum Arabic, or Senegal. The proportion of the size must be adequate to the occasion, for if the different parcels of the size differ greatly in strength, no positive rule can be laid down. When the mixture is made for grounds, the water shoud be made as strong of the size as will admit its being commixt with the whiting, and, to save expense, the gum Arabic is sparingly used, or almost wholly omitted in this case. But for the colours designed for painting, a larger proportion must be allowed; though, in this case, that of the size must be diminished; for the mixture must not be too thick and glutinous, as it would prevent the sharpness and clearness of the outline when the colours are laid on either with the print [wood block] or stencil.

In nicer cases, where pencil-work is required, the management of the colours, with respect to the vehicles, must be the same as with the miniature painting for which ample instructions will be found in the first volume of this work.

When varnish is used, it must be formed of oil of turpentine, and the resins and gums which will dissolve in that menstrum.

For common purposes, the following composition may be employed:

“Take of white resin half a pound, of sandarac and mastic each four ounces: Powder them, and then add two pounds of oil of turpentine, and place the bottle in which the mixture is put in a warm place, where it must remain till the resins, &c. be perfectly dissolved. The varnish may be rendered thinner, where necessary, by increasing the proportion of the oil of turpentine.”