By S. G. Lofft, of the Plate Division, Eastman Kodak Co.

With a view to eliminating many of the inconveniences of the ordinary tanks, the Eastman Plate Tank has been designed to meet the requirements of professional and amateur photographers, and is furnished in sizes which may be adapted to all sizes of plates commonly in use up to 8x10.

Some of the leading features in the Eastman tank are, viz: Perfection in construction, durability (being made of brass, nickel-plated, and practically non-corrosive), convenience in loading, complete exclusion of air during development, thus preventing oxidization of developer, maintaining an even temperature, providing for perfect agitation during development, thus securing even development, and, not the least of its advantages is that it enables the photographer to develop with pyro without staining the hands in the least degree.

Each tank is furnished with a carrier or cage, also made of brass, nickeled, holding twelve (12) plates, and a loading device, by means of which plates may be loaded into the cage in absolute darkness if desired. This is a great advantage where orthochromatic plates are in use, as it eliminates the danger of fog while loading and developing.

A hinged cover on the cage secures the plates after loading, and the bail or handle attached to this cover enables one to handle the rack full of plates with facility, and is used to lower cage into tank of developer.

It has been demonstrated that beyond a certain point of dilution, a developer of certain strength and certain temperature will develop a variety of exposures to a proper point in a certain length of time. After a long series of experimenting, it has been discovered that a developer so compounded as to develop in about 30 minutes will cover the widest range of exposures with the most satisfactory results.

The manufacturers of this tank do not claim for it that it will develop all kinds of exposures exactly alike, but while there will be a difference in density between extremes of over-exposure and under-exposure, this slow method of development will equalize such exposures to a remarkable degreee, and average exposures will be developed with such slight variation in printing quality as to be scarcely perceptible.

It will be noticed in using this tank, that the length of exposures may be reduced materially, as it is a well known fact that dilute developer will produce detail in the shadows without over-developing the higher tones where plates have received a minimum exposure, much better than the stronger developer usually employed in tray development. Successful tank development in a given length of time necessitates care in the selection of chemicals that are of a known uniform strength. As many brands of sulphite of soda on the market contain a great percentage of sulphate of soda, and as different makes of carbonate of soda vary greatly in their active alkaline properties, it is recommended that only reliable brands of sodas be used. The accompanying formulae is prepared with Eastman's sodas. Where other sodas are used, it is advised to test their strength by experimental development till it is determined just how much to use to secure the desired strength of development in the time specified.

It is equally important that the temperature be accurately adjusted, as a few degrees one way or another will make a marked difference in the time of development. For instance, a developer that would complete development in 30 minutes at a temperature of 65° would produce approximately the same density in 25 minutes at 70°. A temperature of 65° is. however, as a rule more satisfactory the year around,

Tank Developing for the Professional.

224o as plates do not soften at this point, and the resulting negatives are finer in grain and firmer in texture, as there is no tendency to swell the cells of gelatin beyond a normal degree, as in a higher temperature.

It is important in this connection, that plates be kept in a moderate temperature before and after exposure, as it is obvious that if they are extremely cold, or very warm, they will lower or raise the temperature of the developer, and thus develop slower or more rapidly as the case may be. This, by the way, is important even in tray development, as without doubt the character of negatives is largely influenced by the temperature of the plates themselves.

Within the experience of the writer, one lot of plates developed in the tank in 15 minutes in a normal 30 minute solution, owing to the fact that the plates were kept in a changing room that was exposed to the heat of the sun, and were really warm to the touch. The resulting negatives were rather flat and heavy, and lacking in brilliancy and the delicate gradation that is desirable.

It will thus be seen that temperature plays an important part in tank development, and success cannot be hoped for unless careful attention is given to this detail.

Where several tanks are in use for developing a large number of plates, enough water to fill all the tanks can be brought to the desired temperature; then after adding to the tanks the stock solutions, as given in formula, fill tanks with the tempered water to lower embossed line.

After preparing developer as directed, load plates into the cage, with the aid of the loading block, being careful to place the first plate glass side out, and all the others facing it, thus bringing both outside plates glass side out, to prevent scratching; remove loader, close hinged cover of cage, and with the bail or handle thereon, lower plates slowly and easily into the developer.

Care should be taken not to stop the plates while lowering into the developer.

To remove any chance air-bells, move the cage up and down half a dozen times after first submerging it without bringing it above the surface of the developer. Clamp the cover on the tank, then take the tank in both hands and reverse rapidly three or four times. This will prevent semi-transparent spots with blended outlines, which are sometimes caused by effervescence in developer or minute particles adhering to the surface of the plate before the film is thoroughly saturated. Then set indicator on dial to point when plates are to be done, thirty minutes ahead of the time the developing begins.

During development, tank should be reversed three or four times to agitate the developer and insure even development, and it will be found that this agitation produces greater brilliancy than if plates remain in one position during the period of development.

After development is completed, the developer should be poured off, and three or four changes of water run into the tank to thoroughly free the negatives from developer; then the cage may be lifted out and placed, with the plates still in it, in the hypo bath, or the plates taken out of the cage and fixed as usual, separately, or the fixing bath may be poured into the tank if desired. If the cage or tank be used for fixing, it should be washed thoroughly, and dried with a cloth; otherwise water remaining on the metal may contain some hypo, which will crystalize on evaporation of the water and give trouble.

In warm weather it will be found quite advantageous to fix the plates in the cage, as then they are thoroughly hardened before handling with the warm hands.

Should the tank leak on being reversed, it will probably be found that the rubber lining in the cover is not in place, or that the tank has been curved in at the top from handling, so it does not fit snugly against the rubber band. This can easily be remedied, and prevented with a little care.

A clean lens, always an important factor in securing clear, bright negatives, is particularly important when using tank method of development.

Tank Developing for the Professional.


As this slow development gives the value of every particle of light that reaches the plate, so it will emphasize the fog or halation caused by a diffusion of light from a hazy lens, and this will be more noticeable than when plates are developed in stronger solutions.

Probably more negative troubles come from hazy lenses than from any other one source, as there is nothing so neglected by the average photographer as these delicate and important instruments of his profession.

It is not sufficient that the outside surface be wiped off occasionally, but it should be done regularly and carefully, inside as well as outside, as it will be found on examination that there is an accumulated deposit on the inner surface of the lenses, which, acting in a modified way like a ground-glass surface, diffuses light all over the plate during exposure, and produces fog, halation, and flat, gray negatives.

To sum up successful tank development, even with a perfect tank, necessitates care in the selection and character of the chemicals used, regulation of the temperature of plates and developer, and keeping your lenses clean.