Developer A. Make up the following solutions: -

(a) Ammonia, '880 .. .. 1 dr. Water........ 9 dr.

This is a 10 per cent. solution.

(6) Potash bromide .. .. 24 gr. Water........ 1 oz.

This is a 5 per cent. solution.

A good commercial gelatine plate properly exposed should develop perfectly with -

Pyro.......... 2gr.

Sulphite ........ 8 gr.

Ammonia, '880 .. .. .. 2 m.

Potash bromide...... 1 gr.

Water to make ..... 1 oz.

or taking the 3 stock solutions -

Pyrogallic........ 20 m.

Solution (a) ...... 20 m.

Solution (6) ...... 20 m.

Water to make...... 1 oz.

Developer B. This is an excellent developer, and gives splendid tones; it is suitable for landscape work or transparencies for the lantern, but is too slow in action for professional studio work. A negative or transparency is not fully developed much under 15 minutes; patience is needed, for any attempt to hasten development will be sure to result in failure.

(a) Common washing soda 480 gr. Potash carbonate .. 480 gr. Potash bromide.. .. 20 gr. Water to make .. .. 20 oz.

A good commercial gelatine bromide plate, properly exposed, either as a negative or a positive, should develop perfectly with -

Pyro.......... 3 gr.

Sulphite ........ 12 gr.

Common washing soda .. 3 gr. Potash carbonate .. .. 3 gr.

Potash bromide...... 1/10th gr.

Water to make...... 1 oz.

Or.

Pyro solution ...... 30 m.

Solution (a) ...... 60 m.

Water to make...... 1 oz.

The proportions given are for 1 oz. of developer; any number of ounces of either formula can be made with the same proportions. With both developers, Col. Dawson recommends half only of the A (a), or half of B (6) being mixed with pyro and water at first, the half in reserve being added as development progresses.

With developer B certain precautions are needed. Plates thickly coated, or rich in gelatine, are apt to blister or frill. Plates prepared without being hardened by alum are apt to frill.

Forcing development is apt to produce blistering.

After } hour or more, the colour of the developer should not be darker than sherry.

Allow time to force an under-exposed plate; you will not find any advantage (but the contrary) in forcing with excess of B.

If a plate developed with A proves under-exposed, wash it well and apply B; this may save it.

If a plate is over-exposed when developed with A, wash it well and continue the development with Pyro solution .. .. 60 m. Solution B .. .. 30 m. Water to make.. .. 1 oz.

With B developer it is absolutely necessary that the plate should be well washed after development, and immersed for 2-3 minutes in Chrome alum .. .. 1 oz. Hydrochloric acid .. 1 dr. Water........ 20 oz. then be again well washed and fixed.

The colour of image is warm black, the shadows as clear as glass, with no stain or discoloration of any kind.

(17) With the pyro ammonia developer, made by the Platinotype Company, use ammonia solution, viz.: -

Ammonia...... 1 oz.

Water........ 2 oz.

Bromide ...... 70 gr.

To develop a half-plate, take 2 oz. water and add 80 drops of sulpho. pyro (every 10 drops of sulpho. pyro contain 1 gr. pyro) and 6-8 drops of ammonia solution. Flood over the plate, and watch till the picture appears. This developer is slow, and takes a minute or so to appear; when the image is well out, add 10 drops more ammonia solution, and keep on till dense enough, which is soon learnt. (18) Usual Pyro Developer.

(a) Strong liquid ammonia 1 3/4 oz.

Potassium bromide .. 240 gr.

Water ...... 80 oz.

(b) Pyrogallic acid .. .. 30 gr.

Water ..... 10 oz.

In case of an ordinary exposure, mix equal volumes. (19) Beach's Developer.

Pyro Solution.

Warm distilled water .. 2 oz. Soda sulphite ...... 2 "

Dissolve; and when cold, add

Sulphurous acid...... 2 "

Pyrogallic acid .. .. .. 1/2 "

Potash Solution.

(a) Water........ 4 "

Potash carbonate .. 3 "

(6) Water........ 3 "

Soda sulphite .. .. 2 "

(a) and (6) are now combined into one solution, which will measure 8-9 fl. oz. To develop an 8 1/2 x 6 1/2 plate which has had a drop-shutter exposure, take 3 oz. water, and add thereto 1/2 oz. of (a) and 3 dr. of (6) of the potash solution, increasing the latter to 5 dr. in case the image hangs back. For a plate which has had the proper exposure, or which has been somewhat over-exposed, add to the 3 oz. of water 3 dr. of (a) and 1 dr. of (6). After a minute's time, if the image fails to appear, add a second dram of the potash, repeating the additions at intervals of a minute until developing commences.

(20) Oxalate Developer.

(a) Saturated solution of neutral potash oxalate. To 1000 parts of this add 3 of saturated solution of ammonium bromide.

(b) Saturated solution of iron sulphate. To 1000 parts of this add 2 parts saturated solution of tartaric acid.

For use, take 4 parts of (a) to 1 part of (6). If picture is under-exposed, add a little more of (b).

(21) Sulphite Developer.

A. Soda sulphite .. .. 4 oz. Water ...... 40 oz.

Dissolve; add sufficient of a saturated solution of citric acid to produce a slight acid reaction upon litmus paper; now add 1 oz. pyrogallic acid, and make up bulk to 54 oz. with water. This gives a solution, each oz. of which will contain about 8 gr. of pyrogallic acid.

B. Ammonia, 880 .. 1 oz. Potash bromide .. 180 gr. Water ...... 40 oz.

Equal parts of this will give a 4-gr. pyrogallic solution, a strength which is a good average. (22) Warnerke's Sulphite Developer.

(a) Potash carbonate.. 45 gr.

Sodium sulphite .. 12 "

Water...... 1000 "

(b) Pyrogallic acid .. 12 "

Sodium sulphite .. 24 "

Citric acid .. .. 2 "

Water...... 1000 "

For a normal development, equal proportions of (a) and (6) are used. (23) Pyrogallic Solution.

Pyrogallic acid.. .. 1 oz. Citric acid .. .. 60 gr. Water ......109 oz.

Dissolve the citric acid in water, and add the pyrogallic. The solution will contain 4 gr. pyrogallic to the oz. of water, and will keep good for months. For convenience, half the quantity of water may be used, when the strength will be 8 gr. per oz. In using it, dilute according to formula employed.