After the reversing solution has done its work, the plate should be washed for a minute or two, the easiest way being to fill the dish with water, rock gently, throw away the water and refill, and repeat this treatment. When dealing with the autochrome plate it must be remembered that the film is extremely tender and that a strong stream of water from a tap may damage it. The second developer may be the same as that used for the first time, or the following recommended by MM. Lumiere:

Sodium sulphite, dry 15 g.

Amidol 5 g.

Water to 1000 ccm.

The silver bromide must be exposed to white light, such as daylight, to bring it into a developable condition. The plate should be covered with the developer and exposed in the dish to daylight until the bromide is completely developed. If development has been put off until evening one has not, of course, daylight available, and any white light may be used, such as gas, electricity or a small piece of magnesium ribbon. Here there is no chance for overdevelopment, but there is decided chance of underdevelopment, so that one should not be in a hurry to stop this process, and the plate should be exposed to white light all the time. The disadvantage of underdevelopment is that, if the picture is subsequently fixed, any unreduced bromide will be dissolved and the stopping-out power of the silver lowered.

Intensification

If the exposure is correct, and the reversal and second development properly carried out, there is no need to intensify, and the picture may be considered to be finished. But if the picture appears weak it may be intensified. The original method was physical intensification with silver, for which three solutions are required:

A. Citric acid 3 g.

Salicylic acid 0.5 g.

Pyrogallol 3 g.

Distilled water 1000 ccm.

B. Silver nitrate 10 g.

Distilled water 100 ccm.

C. Potassium permanganate 1 g.

Distilled water 1000 ccm.

While many workers have experienced trouble with this process, it is very easily carried out, provided a few simple points are carefully observed.

In the first place the plate must be free from the slightest trace of the second developer. To ensure this it is best to mix one part of the reversing bath with 100 parts of water, then flood the plate and rock not longer than five seconds, and immediately pour off and wash with four or five changes of water. The actual intensifier is:

A solution 900 ccm.

B solution 100 ccm.

Naturally, only enough will be used to cover the plate; the mixed solution should be poured over the plate and the dish rocked to and fro for not longer than thirty seconds. Then pour the solution away and examine the plate by transmitted light; if it looks brilliant enough, the plate may be subjected to the clearing treatment described later; but if not fresh intensifier should be mixed and again applied. One of the most frequent causes of trouble is economy in this solution; this invariably leads to a muddy looking picture, as the silver is deposited everywhere, on the fingers, the dish and those parts of the picture where it should not be; it is far better to be a little lavish and secure good results. Exactly how far to carry intensification is entirely a matter of opinion. The greater the intensification, the more brilliant the colors; but it is easy to overdo it and then the colors become glaring, and there is at the same time a loss of the more delicate nuances.

After intensification the plate should be washed with repeated changes of water for not less than one minute, then flooded with the neutral permanganate solution C for not more than one minute, and again washed for five minutes; it can then be dried. Unless the plate is properly washed after intensification, the acid in the film will cause the permanganate to dissolve the image to some extent. Another cause of trouble is the precipitation of minute crystals of silver in the B solution, or on the lip of the bottle, which are washed off on pouring out the solution. Care should be taken not to disturb any deposit, and it is better to suck up the required quantity with a pipette from near the top of the stock.

As an alternative the following method of intensification may be used:

Cupric sulphate 20 g.

Potassium bromide 20 g.

Hydrochloric acid 5 ccm.

Water to 1000 ccm.

The picture is bleached in the above, which takes but a minute, then rapidly rinsed with three or four changes of water and flooded with a five per cent solution of silver nitrate to which a few drops of nitric acid have been added. In fact, any intensifier, except those like uranium, which give a colored deposit, may be used.

Fixation And Drying

If the picture has not been intensified, there is not the slightest need to fix it, but after intensification it must be fixed, and the following is a suitable formula:

Hypo 100 g.

Sodium bisulphite solution 50 ccm.

Water to 1000 ccm.

About three minutes immersion is ample, and then it can be washed and dried. Rapid drying of an auto-chrome is important, as otherwise green patches may make their appearance at the edges of the picture, and occasionally elsewhere. A good plan is to take hold of the plate firmly by the edges and then, with the arm at full length, jerk the plate rapidly up and down so as to sling off as much water as possible. Then dry the glass and, if you have a fan, place the plate at some little distance from this so as not to have too strong a draught impinging on the film. If this is not available, the plate should be placed film outwards against the wall or supported with the lower edge resting on a few thicknesses of blotting paper. If the plate is dried in a strong current of air, the film has a tendency to curl at the edges, and if dried by heat there is a very good chance of the film melting. In no case must alcohol be used for drying, as this will invariably lead to one or more of the dyes being extracted from the colored screen-elements, with local patches of incorrect color as the result. It may be taken as an axiom that alcohol must be avoided with all combined screen-plates.