The colours used in transparent painting are mixed with megilp as a vehicle, except in the case of very light colours, when turpentine and copal varnish must be used. The material upon which transparencies are executed is fine muslin; and this, before being worked upon, should be strained in a straining frame, and sized with either gilders' size, isinglass size, or fine colourless gelatine dissolved and properly diluted. After the first coat of size is dry, the muslin will slacken and hang loosely on the frame. It should be stretched; another coat of size applied; and, when dry, the muslin again extended. A small piece of muslin should at the same time be prepared as a trial-piece, strained in the same way as the larger piece, and when dry it can be used to determine whether the muslin is sufficiently sized, or whether the colours are in working condition. The design having been prepared, it may be traced, copied, pounced or stencilled upon the prepared muslin, care being taken that the outline from which the tracing is made consists of strong and decided lines, that stencil plates are made of oiled paper, and that powdered charcoal is used in preference to any other powder for pouncing.
The instructions for oil painting will apply equally to painting transparencies, except that for very fine tints sponge can be used with great advantage to rub in broad flat tints, however delicate. Fine effects may be produced by the use of two transparencies, arranged one behind the other. On the front surface is painted all that is required to be seen in the clearest relief, the painting on the surface behind, being modified in its effect by being seen through the front surface.