_Print cleaning_ (Vol. iv., p. 175.).--The following method is given as
infallible by Mr. Stannard in the _Art-Union_ for 1847, pp. 179. 261.:
"Immerse the print for an hour or so in a lye made by adding to
the strongest muriatic acid its own weight in water, and to three
parts of this mixture adding one of red oxide of lead, or black
oxide of manganese. A print, if not quickly cleaned, may remain in
the liquid twenty-four hours without harm. Indian ink stains
should in the first instance be assisted out with hot water.
Pencil marks, if carefully done, should be partially rubbed out
with India rubber or day-old bread; that is, if it can be safely
done, as rubbing an engraving is always hazardous. If the print
had been mounted, the paste on the back should be thoroughly
removed with warm water. The saline crystals left by the solution
may be removed by repeated rinsings with warm water."