Important: Safety Warning
This page describes trade processes that use dangerously toxic materials such as cyanide solutions, mercury amalgams, or strong acids. These processes require training, equipment, and precautions far beyond what the text describes.
In addition, this page directs the use of hazardous substances — such as benzine, gasoline, lye, or strong acids — for household tasks. These materials are highly flammable, corrosive, or poisonous, and the practices described have caused fires, burns, and poisonings.
This information has been left in for historical purposes but should not be acted upon.
Engravings
In commencing to restore an engraving, some attention must be given to the kind of injury it has suffered. A general brown color more or less deep, resulting from atmospheric action only, is the least possible change. Spots and stains, caused by ink, colored fluids, oil or insects, must be first treated, and all pencil marks removed by Indiaby Indiarubber or bread-crumbs. A fluid acid, obtained by dissolving 1 oz. of crystals of oxalic acid in pt. of warm water, may be used for application to all stains, and the paper should be wet with it thoroughly where spots of any kind exist.
Excepting in a few cases, this acid will not cause the removal of stains immediately, but generally it combines with the bases of them, and they are removed by subsequent steps; the thorough wetting should be done a few hours before proceeding to clean the engraving. The engraving should be placed in a shallow tub or other vessel, and allowed to rest upon a piece of open cotton stuff, or millinet. This material of suitable dimensions, should have 2 rods or sticks sewn to opposite edges. These sticks will hang over the sides of the vessel, and permit the prints to be withdrawn or moved without any risk of injury, and they should remain in soak with warm or cold water for 12 or 24 hours. When the prints no longer discolor the water on being agitated, the fluid should be withdrawn, and enough clean water added to cover them. Half a pound of chloride of lime should be made into a paste with cold water, and stirred up with 2 qts. of water, and allowed to settle for 6 hours. Part of the clear solution should be added to the bath till the smell of chlorine is perceived, and the prints should be moved to facilitate the action. In very bad cases, 1 oz. of muriatic acid mixed with a pint of water