The war had not been going very long before the photographer discovered that the chemicals most necessary in his business were imported from foreign countries, notably Germany, and that those of domestic origin were few and of the least importance at that.

Developing agents, most vital in photography, rapidly became scarce and prices almost prohibitive. Where standards had to be maintained there was no limit to the price a photographer would pay for certain developers if he were fortunate enough to find any for sale.

With such a scarcity of chemicals and such an opportunity for high prices it is not suprising that many substitutes were offered, some with extravagant claims for equality at least, and often for superiority over the pre war favorites. Prices, of course, were charged accordingly and good money was paid for some low priced substitutes.

It is undesirable that the essential chemicals in photography should be exploited in this manner and it will be interesting perhaps to know how the Eastman Kodak Company - who have many developers offered them, decides upon the merits of a substance for which developing qualities are claimed.

Artura Print, From An Eastman Portrait Film Negative By Dudley Hoyt New York.

Artura Print, From An Eastman Portrait Film Negative By Dudley Hoyt New York.

To be passed by the Kodak Research Laboratory, a developer has to undergo a very searching examination and must measure up to a very exact standard. From the following it will be readily seen that a developer is not a guess work mixture.

A chemical which is claimed to be a developing agent is handed to a chemist, and chemists by training are naturally suspicious, always in a "show me" state of mind. The first thing he does with the would be developer is to compare its physical properties with the required standard. It must be without an appreciable odor - a strong smelling developer is not desirable. It must be light colored and it must dissolve readily in hot and cold water and in solutions of carbonate and sulphite of sodas. Its solubility in the last two should be at least 150 grains in 35 ounces of water, preferably 300 grains.

Experiments are then made, using the substance as a developer with and without an alkali (carbonate or caustic) the results being carefully noted.

For exact tests all developers are made up so that they will contain the same relative amount of the developing agent. Standard amounts of sulphite and alkali are also used. The developer is first tried without any bromide and then with different concentrations of bromide. One of the most important characteristics of a developer is its susceptibility to bromide. Along with the rapidity with which it oxidizes, it is the principal factor in determining the efficiency of a developing solution. Different developing agents are affected to different degrees and in different ways by bromide. There is a very complete method of investigating this. Thus of the well known developers - Hydrochinon, Elon, Pyro, Tozol, Amidol, Paramido-phenol, Kodelon, many are of a like nature. But, as is well known, hydrochinon is most affected by bromide, if all are used at relative strengths and with like amounts of alkali. In many cases the behavior of a developer toward bromide is sufficient to isolate the substance from others of a rather similar photographic quality.

All the tests are made on a standard emulsion with which all the best developers have been used. This emulsion is coated very evenly on strips of special plate glass.

Development is carried out in a water jacketed tube maintained at a temperature of 68° F. by a thermostat and centrifugal pump. In most cases the strips are developed in total darkness.

The exposures are on a known and accurately checked scale, increasing by powers of two, that is, each exposure is twice the preceding one. The development is carried on for different times, ranging from the first appearance of the image to practically complete development which, with some developers, may take hours.

Artura Print, From An Eastman Portrait Film Negative By Dudley Hoyt New York.

Artura Print, From An Eastman Portrait Film Negative By Dudley Hoyt New York.

The above set of experiments provides a great deal of information about the substance, which, when fully interpreted, permits a determination of its usefulness for certain kinds of work. The strips when dry are measured for the density corresponding to the different exposures. This is carried out in a modified photometer and the values obtained are used for determining the efficiency of the developer under different conditions.

Contrast is plotted against time of development and the speed of the reactions determined. The greatest amount of contrast and density obtainable are noted and compared with certain standards. The speed and latitude of the plate with the given developer are important factors. The growth and distribution of fog can be seen from the above series of plates. The relation between dilution and time of development for a standard contrast is found by further experiments.

The behavior of a developer with change of temperature is important and varies greatly with different substances. To determine this, development is also carried out at a lower and a higher temperature than the standard temperature of 68° F.

The penetration of the developer and the depth at which most of the silver grains lie in the gelatine is seen from microscopic sections cut through the film.

An important point in a developer is its keeping quality both before and after use, and this is carefully measured in a standard way. This is especially important in motion picture work where the film is developed on a reel and exposed to the air much of the time.

The color of the image and any staining properties are carefully noted.

If a developer is thought to be suitable for paper, similar, but more limited experiments are carried out and its performances are watched as closely as when developing plates.

From the nature of the tests outlined it is seen that a developing agent must fulfill rather strenuous requirements.

With the present unsettled conditions and with prices much above normal, photographers should not be led away by extravagant and unfounded claims. If they are not in a position to determine the quality and quantity of work produced by a certain developer they should rely on the product of a manufacturer who has safeguarded their interests by offering only those developers which have passed the most exacting requirements of laboratory and practical tests.

Modern Portraiture

Most things can be anybody's gift - your portrait is distinctively, exclusively yours.

Modern Portraiture StudioLightMagazine1917 44Modern Portraiture StudioLightMagazine1917 45From An Artura Iris Print By Campbell Studio New York.

From An Artura Iris Print By Campbell Studio New York.