The size may also be effectually removed from the Print by the common Carbonate of Soda used in washing, although the former process is recommended as the most secure. Dissolve about a handful of the Soda in a pint of water, and when the milky deposit, if any occurs, has subsided, immerse the washed Positives for twenty minutes or half an hour. The Soda renders the paper quite porous, but produces no alteration of tint. If the process be properly performed, ink will _run_ in attempting to write upon the back of the finished picture. After removal from the Soda Bath a second washing will be required, but the time of the first washing may be proportionally shortened. Here a difficulty will occur with many kinds of water; the Carbonate of Soda precipitating _Carbonate of Lime_, in the form of a white powder which obscures the picture. To obviate this, use _rain water_ until the greater part of the alkaline salt has been removed, and do not allow a stationary layer of liquid to rest too long upon the Print. The New River water supplied to many parts of London, being comparatively soft, answers perfectly, and produces no white deposit, if the proofs are moved about occasionally. When the Prints have been thoroughly washed, blot them off between sheets of porous paper and hang up to dry. Some press them with a hot iron, which darkens the colour slightly, but does so in an injurious manner when Hyposulphite of Soda is left in the paper. Albumen proofs when dry are sufficiently bright without further treatment; but in the case of plain paper, salted simply, the effect is improved by laying the Print face downwards upon a square of plate-glass and rubbing the back with an agate burnisher, sold at the artists' colour-men's. This hardens the grain of the paper and brings out the details of the picture. Hot-pressing has a similar effect and is often employed. Mount the proofs with a solution of Gelatine in hot water, freshly made; the best Scotch glue answers well. Gum water, prepared from the finest commercial gum, and free from acidity, may also be used, but it should be made very thick, that it may not sink into the paper, nor produce an unpleasant "cockling up" of the cardboard, which is caused by the damp and expanded print contracting as it dries.