No. I

Neutral oxalate of potash. ............ 1 lb.

Water............................... 5 pints.

Acidify with oxalic acid and filter.

No. 2.

Protosulphate of iron................ 1 lb.

Water............................. 2 quarts.

Filter and add 60 drops suphuric acid.

No. 3.

Bromide of Ammonium................ 1 oz.

Water................................10 oz.

The developer is prepared by mixing together in a graduate the quantity necessaiy to cover the plate in the following proportions:

Oxalate solution..................... 3 parts.

Iron solution...................... 1 part.

Bromide solution.................... 1/8 part.

For instance, it will take about 8 ounces to cover an 8x10 plate in a flat dish; to make this quantity take of the

Oxalate........................... 6 oz.

Iron............................ 2 oz.

Bromide............................ 2 drs.

Always pour the iron into the oxalate solution, then add the bromide, and having placed the exposed plate in the dish pour the developer upon it, covering the surface of the plate as quickly as possible and removing any air bells that may stick to the surface.

Keep the solution in motion on the surface of the plate and in a short time the image will begin to appear, the high lights first, then the intermediate shades, last of all detail will be seen in the shadows. Now pour the developer off, take the plate out of the tray and look at the back of it. If the subject or image can be distinctly seen it may be considered finished and only needs to be washed and fixed.

If the plate has been over-exposed, which will be indicated by the image appearing quickly, wash off the developer with water, add more bromide to the solution and immerse the plate again.

If, on the contrary, the plate has not had enough time, it will be indicated by developing very slowly and with a very thin and weak image; when such is the case add more of the iron solution, however, not more than to make the proportion of the iron nearly one-fourth of the whole solution. More than this proportion will cause a yellow precipitate, which will settle on the surface of the film and destroy it. If by this course you succeed in securing sufficient detail in the shadows, the negative may afterwards be strengthened.

It is as well, however, when a plate is found to be undertimed (and it is possible to make another from the same subject) to throw it away; it will scarcely repay further attention.

It will be seen that a considerable margin in time of exposure can be allowed and provided for. Yet none the less it is of the utmost importance to learn to give the correct and proper exposure to secure the finest results.

This, it is true, is not always possible, and as an under-exposed plate is lost, any error in exposure would better be in too much rather than in too little time.

It is said by some that by the use of citrate of soda almost any degree of over-exposure may be remedied, but there remains the fact that for a restraining agent to be of any value its application to a negative in development must be almost instantaneous upon the earliest discovery of the over-exposure.

When a large number of plates have been exposed and the first developed indicates that all have been overtimed, then a 50 per cent, solution of citrate of soda, used with judgment, might result in saving the lot.

When over-timing makes itself visible unexpectedly and it is feared that the development will have proceeded too far before the retarder can act, a good plan is to take the plate out of the dish and flow over it a solution of citric acid, containing a little chrome alum, which will immediately stop the action of the developer and give time to make other arrangements.

Ammonia Pyro Developer

No. 1

Pyrogallic acid....................... 1 oz.

Alcohol............................. 4 oz.

No. 2

Water...............................60 oz.

Bromide of ammonium................60 grs.

Strong liquor ammonia............... 2 drs.

To use, take of

No. 1 or pyro solution................ 1 dr.

No. 2 or ammonia solution..............10 oz.

This will be enough to develop three or four 8x10 plates, if they are properly timed.

The above is one of the best forms of ammonia pyro developer; it gives negatives of very fine quality.

Many dry plates, on development with ammonia and pyro, show a green fog by reflected light, and a pink or red fog by transmitted light; this fog does not materially injure the printing quality of the plate, but spoils its appearance to the eye, and for that reason many establishments have given up the use of ammonia and in its place use soda or potash.