[ [4]See foot-note to [page 30].
Mix equal parts of ortol solution and soda solution.
This developer behaves in much the same way as pyro-soda and gives very similar results. It has the advantage, however, that it does not stain the fingers, and has practically no tendency to produce either fog or stain on the plates. Moreover the same quantity of solution can be used for several plates; when the action becomes perceptibly slower or weaker, part of the old solution is poured away and an equal quantity of freshly mixed ortol and soda solutions is added.
The chief differences to be observed are (1) that the different parts of the image follow one another more rapidly than with pyro-soda, even though the plate may have been correctly exposed, and (2) the colour of the reduced silver is somewhat bluer than with pyro-soda, and therefore in order to obtain the same degree of printing opacity, as distinct from visual opacity, development must be carried a little further.
Apart from these differences, what has been said of pyro-soda holds good for ortol soda and need not be repeated.
| DEVELOPMENT WITH HYDROQUINONE (QUINOL). Quinol Solution. | ||||
| Hydroquinone | 90 | grains or | 2 | parts |
| Sodium sulphite | 1 | oz. or | 10 | parts |
| Water to make up to | 10 | oz. or | 100 | parts |
Alkali Solution. | ||||
| Potassium carbonate (dry) | 1 | oz. or | 10 | parts |
| Potassium bromide | 20 | grains or | 0.46 | parts |
| Water to make up to | 10 | oz. or | 100 | parts |
Mix two parts of hydroquinone solution with one part of alkali solution and one part of water, or, if a more energetic developer is wanted, mix equal volumes of the hydroquinone and alkali solutions. Hydroquinone is not an advantageous developer for general purposes, but it is useful when negatives are required showing strong contrast between the highest lights and the deepest shadows, and especially when it is important that there should be no deposit at all in the deepest shadows. This is the case, for example, when copying line engravings, pen and ink drawings and similar subjects.
DEVELOPMENT WITH FERROUS OXALATE.
This method of development also is not well adapted for general work, but it is invaluable for certain purposes. The reduced silver has a pure grey-black colour and there is exceedingly little tendency to produce fog of any kind. On the other hand, the developer admits of little modification in its composition and therefore the exposure must be fairly correct. It is also important to avoid contamination with even minute quantities of hypo, since this substance very readily causes stains.