The use of a yellow instead of a ruby light for those photographic operations which require what is called a dark room, has been spreading considerably. It is, however, sometimes assumed that although a yellow light may safely be used for developing, a red or ruby coloured illumination is necessary for the preparation of the plates.
If, however, as many experiments seem to show - notably those of J. R. Sawyer, described at the June meeting of the Photographic Society of Great Britain - yellow and orange light have less effect upon a sensitive plate in proportion to illuminating power than red light, it is difficult to see how the latter should be safer or better for any part of the work of plate making; and the practice of some of our most advanced workers is to use yellow light alone for all photographic operations. W. Cobb, whose views of London are amongst the most remarkable instantaneous photographs that have been seen, and who has succeeded in preparing plates of most extraordinary rapidity, recently stated that he used yellow light in his coating room, and fonnd that even a prolonged exposure to its rays had not affected plates which were exposed to it.
Of all the yellow mediums tried, none, when used alone, gives at the same time so strong and safe a light as that which is known as golden fabric. It is so very translucent that several thicknesses may be used, and still sufficient light transmitted for satisfactory working; 4 folds over a small window will be found to afford an ample light; whilst if the sun shine upon the window, extra thicknesses may be applied, and still far more light to work by, will be admitted than with the lauded ruby. For artificial light, 1, 2, or 3 thicknesses may be used, according to the power of the light and the sensitiveness of the plates to be dealt with.
It is obviously desirable with this, as with all textile fabrics, to have a sheet of glass in front, to protect it from splashings; and the outer fold should be examined occasionally, and, if at all faded from exposure to light, changed. (W. £. Debenham.)