TRANSFERRED IMPRESSIONS. Frequently the characters of a book, bound before the ink is completely dry, offset, while in press, an impression in grayish tones upon the opposite pages or upon the faces of inserted prints. These transferred impressions may sometimes be removed by rubbing with an eraser made of bread crumbs or by soap-jelly, which should be left on for some time and then washed off.
I have no doubt neglected to describe more than one kind of spot which an amateur may find. By analogous reasoning, however, he may find for himself the proper remedies to use. If the spot seems to be of a vegetable or animal nature, he should use chlorine and sulfuric acid; if metallic, diluted hydrochloric acid; if oily or greasy, essence of turpentine, ether, alkaline solutions or benzine.
BLEACHING.[9] Soaking a print in cold water for about twenty-four hours often suffices to brighten and clear it; but if, after a long soaking, it still remains darkened to the point of detracting from the clarity of the engraving, one will need to use chemicals in order to obtain a suitable bleaching. Chloride of lime may be used for this purpose. This is a fine, dry powder which softens when allowed to absorb moisture from the atmosphere. About fifty grammes of this are placed in a bottle about two-thirds full of water, and thoroughly shaken. When the solution clears by the excess of matter depositing on the bottom of the bottle, the clear liquid is carefully poured off. Another solution, which will be weaker, may be made by pouring more water into the bottle. The clear solution is diluted with about twenty times its quantity of pure water, for use. It is better to dilute too much, and add more of the solution later, if necessary, than to dilute too little. The solution will not injure the black ink of an impression, but if too concentrated, it will make the paper brittle.
After using this solution, the print should be placed in a bath of weak acid, and then left to soak for several hours in clear water.
CHAPTER III
REBACKING
