BRUSH TONING A method of toning in which the solution is applied by means of a brush. This method is occasionally adopted for large prints. A con centrated solution is employed and the print, after washing, is laid on a sheet of glass and the solution rapidly brushed over its entire surface. It is desirable to cover the print with the toning solution as quickly as possible, and each stroke of the brush must slightly overlap the part wetted by the preceding stroke ; also, no part of the print must be left uncovered in the first application, or uneven toning will result. The brush strokes are first made along the print, then across, and then diagonally, continuing the work until the toning is completed.
Prints, particularly those on bromide paper, can be brush-toned to two or more colours. The method is widely used for the rapid toning of ordinary gelatine or collodion P.O.P., and almost every formula can be adapted, but the following is considered to be the most suitable. Four stock solutions are necessary : No. x. Ammonium sulphocyanide r oz., water to 9 oz.
No. 2. Sodium phosphate r oz., water to 9 oz.
No. 3. Saturated solution of borax.
No. 4. Gold chloride solution r gr. to r drm.
To make up a working mixture take 14 minims of No. I and make up to i drm. with water ; then add 12 drops of No. 4 very slowly, shaking the mixture after each drop is added. Then add 6 minims of No. 2, and finally 16 minims of No. 3. Each ounce of the working solution referred to above contains practically 7 grs. of sulpho cyanide, r gr. of gold chloride, 5 grs. of phosphate, and 7 grs. of borax, and the bath, if desired, may be made up by adding these quantities to each ounce of water used. By this method, the print exactly as it comes from the printing frame, is placed on a sheet of glass or pinned to a board, and the working solution brushed quickly and evenly over it with a camel-hair mop. Toning should be complete in about two minutes, after which it is washed and fixed as usual.
Great care should be taken not to expose the print to kl strong light during the process of toning as otherwise there will be a risk of discolouring the whites.