Manufacturer and builder 11, 1885
Where it is requisite to remove painting entirely from its ground, it is usual to resort to mechanical scraping, etc., or to the very dangerous operation of setting fire to the painted surface immediately after washing it over with oil of turpentine, called turps, and operation that may be safely and more easily accomplished by laying on a thick wash or plaster of fresh-slaked quicklime, mixed with soda, which may be washed off with water the following day, carrying with it the paint, grease, and other foulness, so that when clear and dry, the painting may be renewed as on fresh work. Clear colling is sometimes resorted to over old painting, for the purpose of repainting, in which case the surface exposed to the sun's rays or alterations of temperature is liable to become blistered and scale off. Varnish may be removed by friction - if it be a soft varnish, such as that of mastic, the simple rubbing of the finger-ends, with or without water, may be found sufficient; a portion of the resin attaches itself to the fingers, and by continued rubbing removes the varnish. If it be a hard varnish, such as that of copal, which is to be removed, friction with sea or river sand, the particles of which have a roundness that prevents their scratching, will accomplish the purpose. The solvents commonly employed for this purpose are the several alkalies, alcohol, and essential oils, used simply or combined. Of the alkalies, the volatile in its mildest state, or carbonate of ammonia, is the only one which can be safely used in removing dirt, oil, and varnish from a picture, which it does powerfully; it must therefore, be much diluted with water, according to the power required, and employed with judgment and caution, stopping its action on the painting at the proper time by the use of pure water and a sponge. A thick coat of wet fuller's earth may be employed with safety, and, after remaining on the paint a sufficient tume to soften, the extraneous surface may be removed by washing, leaving the picture clean. An architect of the author's acquaintance has succeeded in a similar way in restoring both paintings and gilding to their original beauty by coating them with wet clay. Ox-gall is even more efficacious than soap.
In filling cracks and replacing portions of the ground, putty formed of white lead, whiting, varnish, and drying oil, tinted somewhat lighter than the local colors require, may be employed, and in some cases, also, plaster of Paris. In restoring colors accidentally removed, it should be done with a vehicle of simply varnish, because of the change of tint which takes place after drying in oil.
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