Take 2 ozs. of tripoli, reduced to fine powder; put it into an earthen pot or basin, with water to cover it; then take a piece of fine flannel, four times doubled, lay it over a piece of cork or rubber, and proceed to polish your varnish, always wetting it with the tripoli and water. You will know when the process is completed, by wiping a part of the work with a sponge and observing whether there is a fair and even gloss. Take a bit of mutton-suet and fine flour, and clean off the work. Or, the powdered tripoli may be mixed up with a little pure oil, and used upon a ball of serge, or of chamois leather, which is better. The polishing may afterwards be completed with a bit of serge or cloth, without tripoli. Putty powder, and even common whiting and water, are sometimes used for polishing; but they produce a very inferior effect to tripoli, except in the case of ivory, for which putty and water, used upon a rubber made of a hat, forms the best and quickest polish. Putty and water may likewise be used, in the same manner as just mentioned for ivory, in finishing off the polish of pearl work, after it has first been polished very smooth with pumice-stone, finely powdered, and well washed to free it from impurities and dirt. 538. VARNISH FOR COLOURED DRAWINGS Mix together 1 oz. of Canada balsam and 2 ozs. of spirits of turpentine. Before applying the composition, size the drawing or print with a solution of isinglass in water; when this is dry, apply the varnish with a camel's-hair brush. The use of this varnish gives to coloured drawings and prints an appearance resembling that of oil paintings. 539. VARNISH FOR GLASS Reduce a quantity of gum tragacanth to powder, and let it dissolve for twenty-four hours in the white of eggs well beat up; then rub it gently on the glass with a brush. 540. TO CLEAN PICTURES Having taken the picture out of its frame, take a clean towel, and making it quite wet, lay it on the face of your picture, sprinkling it from time to time with clear soft water; let it remain wet for two or three days; take the cloth off, and renew it with a fresh one; after wiping your picture with a clean wet sponge, repeat the process till you find all the dirt soaked out of your picture; then wash it well with a soft sponge, and let it get quite dry; rub it with some clear nut or linseed oil, and it will look as well as when freshly done. 541. ANOTHER METHOD Put into two quarts of strong lye a quarter of a pound of Genoa soap rasped very fine, with about a pint of spirits of wine; let them simmer on the fire for half an hour, then strain them through a cloth; apply it with a brush to the picture, wipe it off with a sponge, and apply it a second time, which will effectually remove all dirt; then, with a little nut oil warmed, rub the picture, and let it dry; this will make it look as bright as when it came out of the artist's hands. 542. VARNISH FOR CLOCK FACES, &c.