In an ordinary room, at about the distance from the window at which we recommend portraits to be taken, the exposure will be five to ten seconds. It is far better to work with such exposures which are under control than with the very brief ones which may be given with a brighter light.
For development the following solutions are mixed :— No. 1.
Oxalate of potash . 1 lb.
Bromide of ammonium . 320 grains.
Warm water, up to . 80 ounces.
No. 2.
Proto-sulphate of iron 4 oz. 250 grains.
Water, up to . 80 ounces.
When prints are exposed a dish is taken somewhat larger in size than the prints to be developed. Enough developer is made by taking equal proportions of Nos. 1 and 2 to fill the dish to a depth of at least half an inch. In mixing the solutions, No. 2 must be poured into No. 1, not vice versa. Doubtless the photographer will recognise the developer as a modification of that used for dry plates, and called the "ferrous oxalate" developer.
The prints are placed dry into the solution, not more than three or four at a time. They must then be kept in constant motion. The development goes on more rapidly than that of a dry plate, and it is necessary to watch intently as it gets near completion. The print must be taken out of the solution immediately that it has got as dark as it ought finally to be ;—if anything before rather than after it looks dark enough, because whereas no depth is lost in toning and fixing, develop ment is liable to continue for a second or two after the print is removed from the developing bath.
The print, as soon as development is over, is placed in a dish of clean water, and is rapidly transferred to a second and then to a third dish, each containing clean water. It then goes into a fourth, where it may remain for three or four minutes.
The developer must not be used within more than about a quarter of an hour of the time that the first print has been placed in it ; hut during that quarter of an hour as many prints as is possible may be passed through it.
It is immediately after development that it is first possible to tell whether or not the exposure has been correct. This is ascertained chiefly by the colour which the print assumes during development. The print will
show a colour tending towards red if the exposure has been correct. If it has been too short the prints will be black or of a greenish-black. If too long they will be very red, and will appear weak or lacking in contrast.
It is sometimes desirable to get prints of an engraving black tone. In this case an exposure of only perhaps a third or a quarter of what we have mentioned must he given.
After the prints have been washed they are placed in a bath composed as follows :— Ground alum6 ounces. • Water, up to. 80 ounces.
• The water is poured over the alum hot, but the solu tion must not be used till it has become quite cold.
The prints, after they have been for a quarter of an hour in the alum, are washed as before. They are then ready for toning. They may be toned by the aid of light of the same nature as that in which prints on albumenised paper are toned. Toning is performed in precisely the same manner as in the case of prints on albumenised paper, except that when we wish to judge of the change of colour we look through the prints, holding them in the hand, not down upon them. The surface of the print will have assumed a pm•le tint long before toning is complete.
The prints may be toned in any toning-bath, but as the baths generally used for albumenised paper are very slow in their action on Alpha paper the following bath is recommended : Water 1 pint.
Acetate of soda . . 60 grains.
Chloride of lime (fresh) 4 grains.
Chloride of gold . 2 grains.
The water is poured hot over the acetate of soda and the chloride of lime, and when the solution has become cold the gold chloride is added.
After toning the prints are washed once more. They are then placed for five minutes or longer in a fixing solution, composed as follows :— 113-po 1 lb.
Water . SO ounces.
The colour will change to a foxy red in the fixing bath if the prints have been properly exposed, developed, and toned ; but this red will give place to a colour vary ing from warm brown to rich purple when the prints are dry.