You may have noticed in recent editions of booklets treating on the proper manipulation of films, plates and papers, that our formulas are being designated by letters and numbers in addition to the ordinary designation which had formerly been given them.

This change does not indicate that the formulas are in any way different, and is only intended as a means of more readily identifying a formula no matter where it is found or how large or small its volume may be. If it is the UI developer formula its chemical proportions will always be the same.

In the Seed, Standard and Stanley Plate Booklet, for example, there are five developers containing Elon and Hydrochinon: D28, D29, D31, D61 and D62 and each of these developers has its special uses with certain materials.

If you were using the D1 developer and did not find that it produced exactly the results you wished to obtain with certain materials, you might have occasion to ask for information as to what developer would best suit your purpose. You would only need to mention that you were using the D61 developer and we would not have any doubt as to what Elon Hydrochinon developer it might be. There is only one D61 developer. And for the special result you wished to secure we might suggest the D29 formula. And again there could be no mistake as we have but one D29 developer.

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PORTRAIT FILM NEGATIVE, VITAVA PRINT

By Lee Saylor-Harris Studio Chicago, III.

This designation of formulas is also valuable when, for any reason, it is necessary to make a change in a formula. If the D61 formula is changed in any way it is no longer a D61 formula. It must be given a new designation so the change will readily be apparent in any instructions that may be issued.

Fixing baths are indicated by the letter "F" and a number: rinse or short stop baths by the letters '"SB" and a number, and the same with intensifiers and reducers and toning solutions.

And while we are on the subject we might mention the importance of using only the formulas recommended by the manufacturer. If a developer is compounded from fresh pure chemicals of certain strength, it will very seldom be found that local conditions of water have any material bearing on the action of the developer. There are some few cases that are exceptional, but they are very few.

It is more often the case that the chemicals used are responsible for any variation in the action of the developer. If the photographer uses one of our formulas calling for E. K. Co. Sodium Carbonate, which is 98 1/2% pure Carbonate, and another soda is used which contains only 80% pure Carbonate, it can only be expected that the results will not be what we intended when the formula was adopted.

Under such conditions it would be natural for the photographer to jump at the conclusion that another developer, which called for a larger amount of Sodium Carbonate, was a better developer be* cause it produced a better result, when our developer, compounded with E. K. Co. Sodium Carbonate would have produced identical or even better results because the quantity of pure Carbonate would have been exactly right.

It is very seldom that anything is to be gained by "discovery" developers. Certain chemicals have certain actions on sensitive emulsions and the action of each chemical in various proportions to all the other chemicals is so thoroughly determined by practical, as well as scientific tests in our laboratories, that there is no question as to what a developer that we recommend will do if it is mixed properly with pure chemicals. As an illustration of this thoroughness, our laboratory has made over twelve hundred solutions, and tested each one, in determining the best proportions of chemicals for one formula. And with the carefully tabulated resuits of such a test it is only fair to assume that we know just what formula is best and hat may be expected from such a formula in the hands of those who use our sensitive materials.<

A New Method Of Designating Formulas StudioLightMagazine1923 165

PORTRAIT FILM NEGATIVE, VITAVA PRINT

By Lee Saylor-Harris Studio Chicago, III.

A New Method Of Designating Formulas StudioLightMagazine1923 166