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stains, ounce, solution, acid and water

SQUEEGEE.--A handy contrivance consisting of a strip of flat indiarubber set in a wooden back or handle. It is exceptionally useful for pressing the front in contact when mounting for carbon printing, for glazing gelatine prints, etc., where an even pressure is required. The india rubber should be neither too hard nor too soft, and it should have an even and nerfectly straight edge.

Another form is that known as the roller squeegee. It consists of one or two wooden rollers, covered over with indiarubber and set in a handle. Its purpose is the same. See Figs. 426, 427.

STAINS.—Stains are usually due to careless man ipulation. Pyro stains on negatives developed with that substance can usually be removed with- Chrome alum i ounce Citric acid ounce Water 20 ounces This solution also is useful for clearing negatives or bromide paper developed with ferrous oxalate.

Silver stains upon negatives which sometimes make their appearance if the paper or negative be damp when printing are very difficult to remove. Remove the varnish and apply- Ammonium sulphocyanide 1 drachm Water r ounce Nitric acid ..... ounce Water r ounce A freshly-mixed solution is used for each negative. Afterwards wash well, and immerse in a saturated solution of chrome alum.

Silver stains on the hands may be removed with— Sodium sulphate 1 ounce Lime chloride ounce Water r ounce Mix up well, and apply with an old hard toothbrush.

Pyro stains on the fingers are removable by well washing with a io per cent. solution of oxalic acid.

To remove nitric acid stains from the hands or clothes, touch them with a solution of po tassium permanganate, wash well in dilute hydrochloric acid, and again wash.

Black stains with ferrous oxalate development will sometimes occur if the plate be handled with fingers contaminated with sodium hyposulphite. There is no method of removing them. Yellow stains on prints, after fixing, are generally due to their having stuck together when in the hypo. Some of the silver hyposulphite has not been removed, and changes in the washing waters to silver sulphide, producing yellow stains. Use fresh hypo for each batch of prints.

Dr. Eder has made several experiments with thiocarbamid for removing yellow gyro stains and for preventing green fog, which sometimes makes its appearance on plates developed with amidol. The solution he employs is : Water. woo C. cm.

Hyposulphite of soda 200 grammes Thiocarbamid 15.20 grammes To this solution is added : Acid sulphite lye 3o C. cm.

Or Sodium bisulphite so grammes Negatives must be well washed before fixing.

STAMP PHOTOGRAPH.—Small photographs made with a design and gummed at the back to resemble postage stamps, (see Fig. 428), and are used for many purposes, such as trade marks, business cards, letter heads, etc.

By an arrangement similar to that shown in Fig. 429, a cabinet picture is placed behind the matt or border and a negative made. No focusing is re quired, and there are usually 12 or i6 lenses so that many images are formed. From the negative thus obtained silver prints are made. The pictures are then given per forated edges and gummed at the back to resemble postage stamps.