We do not propose to give the various recipes for the plaster dressing forming the preparation of the panel or canvas. They are different according to time and country and can be found in special works on painting. Under ordinary conditions it is very easy to substitute the missing preparation, just as it is easy to give it the proper surface either by pumice or skilled coating with the brush, but in the case of a painting on canvas it is very seldom that there are not big holes right through it. The first operation in such cases is to recanvas the work, to line it, namely, with another canvas which is pasted to the old one and flattened with an iron till perfectly dry. The missing part must then be filled in, imitating the weave of the canvas on which the work is painted. No easy matter this, as the different weaves of canvases are as characteristic as signatures: no two are ever alike. The new canvas showing through the hole is therefore either covered with a patch of canvas taken from some comer of the painting to be restored, or it is given the same appearance by pressing a piece of the old canvas upon the fresh preparation of the part missing, thus moulding the texture of the threads. This must be done skilfully in such a way that the parallel lines of the threads match. There are some clever fakers who imitate the old canvas by strokes of a hard brush upon the fresh preparation of the new pieces, reproducing the characteristics of the canvas by actually copying from the original part. When a painting is finished there are various methods by which an appearance of age may be given or restored to it. From asphalt to liquorice hundreds of things are used, either dissolved in turpentine or water, glue, albumen, etc. Veiling with varnish, coloured with the proper pigment, generally gives the finishing touch. The imitation of old and cracked varnish is simple enough. First one must give the canvas a coat of diluted glue, then varnish before the glue is quite dry. As the underlayer of glue dries quickly and has a shrinking capacity disproportionate to that of the varnish, it is easy to understand that the result will be a cracking of the varnish. A close or a coarse network of cracks is obtained by increasing or decreasing the inequality of shrinkage between the two layers, or by hastening or retarding the drying of the upper layer by artificial means. Although comparatively easy, these operations nevertheless demand no little experience to be crowned with due success.