Into a glass measure pour t oz. of A and i oz. of B (cautious workers commence with only a half-quantity of B, adding the remainder when the details of the image have appeared). Two oz. of liquid are sufficient for a quarter plate, in a flat-bottomed dish, and 4 oz. for a half-plate. Do not be niggardly in the use of developer. It is cheap enough if the worker makes up his own solutions.
Lay the plate, film upwards, in the developing dish and pour the solution in a flood over it, so as to ensure it being covered all over at once with as few bubbles as possible. Then rock vigorously backwards and forwards for a few seconds, to remove air-bells. Within about a minute, if the exposure has been correct, the image will begin to appear as a faint discoloration which will be recognisable as the sky in a landscape ; or in a portrait the white collar, face, and hands. These high lights go on darkening and become more defined as black patches, and then, still by degrees, the half-tones assume a grey colour, till at last we can recognise all the chief features of the scene, only with the lights reversed. If the plate were to be removed from the developer at this point the image would be so faint as to be of no value whatever ; it must remain for a further period, during which, by electrolytic action, the unchanged molecules of silver salts continue to be reduced till the image has penetrated well into the film towards the back.
Under-exposure.On the other hand, if the image fails to make its appearance, and the full amount of alkali has 7 been added, we must decide that the plate is under-exposed, and therefore not worth troubling about. But if the subject is irreplaceable, and we are content to have a very inferior result rather than none at all, the dish is covered over, say, with a lidless cardboard box of sufficient size to touch the table all round, and so form a thorough protection from light. We may examine at intervals of ten minutes ; but if after half an hour a satisfactory image is not well on its way to completion, hope must be abandoned. No means exist of reinforcing a developer to enable it to define detail on an under-exposed plate.
a plate is suspected of being over exposed m drops of bromide should be added to each ounce of the developer before it is poured over the plate ; and if the image flashes out quickly the solution must be returned to the measure, and a further quantity added. Some workers, on finding after commencing development that the image flashes out at once instead of gradually, and is therefore over-exposed, remove the plate at once into a weak solution of ammonium citrate (5 grs. to the ounce), and after about a minute wash and replace in the developer. Others wash
the plate under the tap, and replace in the developer to which three times the amount of bromide has been meanwhile added. Unless the over-exposure is very serious it need not occasion anxiety, as the resulting negative will print well enough after treatment in a reducing bath. The great mis take of beginners is to over-exposed negatives.
When Development is classes of plates may be allowed to continue in the developer until the lines of the image are plainly visible on the glass side ; but with some thickly coated plates the image never penetrates com pletely through the film. Another test is the commencement of " fog " on the white margin left by the rebate of the dark slide. When held up against the ruby lamp the sky and other portions which are to appear white in the resulting print should be approaching a solid black, and the details in the shadows well marked.
Factor for Timing Development.Mr. Alfred Watkins, the inventor of many valuable instruments for securing exacti tude in exposure and development, has prepared a table showing the factor necessary to calculate the time when development reaches a degree found by trial to give a sufficient amount of contrast. To use the table, multiply the time which elapses between the immersion of the plate and the first appearance of the image. Thus, if the image when we are using a pyro developer 5 grs. to the ounce appears in 45 secs., development should be complete in just under 5 minutes.
Factor.
Adurol . . . . . . . 5 Amidol (2 gr. per oz.) . . . . . 18 Diamidophenol . . . . . . . 60 . . . . . . . . . 12 Edinol . . . . . . . . 20 Eikonogen . . . . . . . . 9 Glycin (carb. soda) . . . . . . . 8 Hydroquinone . . . . . . . 4i to 5 Pyro Soda (1 gr. to oz.) . . . . . 9 to (4 gr. to oz.) . . . . . 4, 8 2 (5 gr. to oz.) . . . . . 3f, Imogen Sulphite . . . . . . . 6 Kachin . . . . . . . . . to Metol . . . . . . . 30 Metol Hydroquinone . . Ortol . to Pyrocatechin . . . . . . . . to Quinomet . . . . . . . . 30 Rodinal . . . . . . . 40 Controlling Development.We have seen that the restrainer increases contrast ; we can diminish contrast by diluting the developer. Dilution renders the action slower, and inci dentally gives the ehance for more detail to appear in the shadows before the high lights have become too dense, and so a softer negative can be obtained. With the normal solutions, if a plate is removed from the developer before the usual time, the contrasts will be very great, and the ' The latter figure with minimum amount of Bromide 2 The latter figure without Bromide.