From the difficulty of judging when the development has reached the right point, in consequence of the opacity of the gelatine film, many negatives are finished before they have acquired sufficient density in development. As a result of this, much attention has been given to the discovery and preparation of redeveloping or intensifying solutions, many formulae for which have been published; among the best are the following:

Intensifying Solution. A

Bichloride of Mercury.............. 120 grains.

Dissolved in hot water . ,.......... 16 oz.

Add to this a strong solution of Iodide of Potassium drop by drop, until the red precipitate begins to re-dissolve, then add a few grains of hyposulphite of Soda, or enough to clear the liquid.

When required for use pour part of this solution into a tray of a suitable size for the plate, add an equal amount of water, then immerse the plate and keep the solution in motion. You will immediately notice a change in the color of the film; take the plate out, and if it has gained enough strength, wash it and set it up to dry; if not, give it more.

It is proper to state that this process is more effective if the plate has been dried after development.

When the plate has been thoroughly fixed and fully washed, it will intensify by this method, without change of color by transmitted light, and it will have secured a lovely printing quality rarely seen even in the most perfect negatives.

This solution may be used until it is exhausted.

roche's intensifier. b.

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

Sulphate of Copper................100 grains.

Bromide of Potassium..............100 "

When dissolved, this solution is ready for application and can be used repeatedly.

The negative, after fixing and washing, is immersed in the solution until it turns white.

Now remove it and wash slightly, then immerse it in old ferrous oxalate developer and allow it to remain until it becomes black entirely through the film. This method gives fine results and good printing color.

Practicalities

Form the habit of noticing carefully the intensity of the illumination of the subject on the ground glass of the camera, so as to judge correctly the time of exposure, as much of the successful working of dry plates depends on the exposure; for although slightly underexposed or much over-exposed plates may by suitable modification of the developer be saved and print good pictures, yet they will lack the glow and balance that are characteristic of the most perfect work.

Use a flat camel's-hair brush to remove any dust from the plate, before putting it in the shield for exposure.

Always keep your developing solution in motion on the plate.

Fix your negative very thoroughly; leave it in the hypo 5 or 6 minutes longer than it is apparently necessary.

Never use hypo after it becomes discolored or turbid and deposits a sediment.

Develop longer than you think necessary; a slow printing negative is preferable to a weak one.

Keep your dark room and its contents very clean and free from dust, and well ventilated.