Shadows may be deeped in a photographic negative, and opaque (or light) lines removed by scraping with a sharp knife as shown in the accompanying sketch. Its edge is turned over slightly so as to scrape away a thin layer of film. The negative must be thoroughly dry and should be warmed slightly, or the film may tear. A much better light is necessary for the use of the knite than for pencil work. Scrape only the least possible amount at each stroke, producing a slight grating sound; the effect should not be visible till after a few strokes. For this work remove the ground glass from the desk. Decided white lines are due to working too heavily or using too soft a lead. Avoid touching the eyes-that is, the iris and pupil. View the effect of the work from all angles by turning the negative round. For thin lines the point may be used, but for broader spaces use the side of the blade. The easiest plan is to stipple in the part with water colour. Mix crimson lake, ultramarine, and black to match the photograph. Soak some lumps of gum arabic in water and melt by warming. Mix well a few drops with the paint; the surface should then have on drying the same appearance as the surrounding parts. It is well to have a cup of thin gum water at hand to dip the brush in occasionally.

Keep the touches as even and close together as possible. Another good plan for deepening the shadows is to rub them down with a leather stump dipped in alcohol. For large patches resort to chemical reduction (hypo and ferricyanide of potash).

Tool for Retouching Negatives.