Doublet Drachm or Dram
» it should be thoroughly well washed free from hypo, or, if dried,
soaked in water for an hour, then intensified by the use of the uranium intensifier (see Intensification), then rinsed once or twice, and an alkaline solution such as I : 20 solution of carbonate of soda may be applied with a camel's hair brush to the dense parts of the negative; and this has the effect of dissolving the uranium intensification and leaving the dense parts, therefore, in their original condition, so that the result will be a negative intensified in the shadows but not touched in the high lights. If necessary the negative may now be dried, and the high lights still further reduced by the local application of Farmer's ferridcyanide and hypo reducer. Vidal has suggested for local intensification or as we call it dodging, painting over the dense parts of a negative with asphalt dissolved in benzine, allowing this to dry, and then dipping the plate into a solution of some aniline dye, like aurantia, chrysoidine extra, Bordeaux red, etc., the strength of the solution and the stay of the negative in the same, being of course adapted to the degree of intensification required ; the gelatine absorbs the colouring matter, and thus the thin parts are locally intensified. If afraid to treat the film in any way for fear of losing it, one may paste the back of the negative with starch paste, and lay it down on a flat sheet of tissue paper with slight pressure, allow to dry and trim the paper down. We have now a surface on which we may work with a crayon and stump, with retouching pencils or water colour. Another method is to coat the back of the negative with matt varnish which has been stained deep red by the addition of some aniline dye, or yellow by dissolving gamboge in it. When the varnish is quite dry, we may scrape it off with a sharp penknife over those parts we wish to print through more and thus get better results. Local reduction may of course be carried out by exactly revers-ing the directions for some of the above processes, but enough has been said to point out the method of procedure to any intelligent operator.
Doublet. This term is applied to lenses which have a glass or combination at each end of the lens tube. Various names have been given to these, or to slight modifications. (See Lens )
Drachm or Dram. See Weights and Measures.