Camera Obscura

Adox negative reduced with Eder’s harmonizing reducer. Please notice the apparition of three horizontal marked bands and a fine vertical weft. This last was present also before the reduction, while the bands where invisible while printing and only appeared after the treatment.

Compared to digital negatives, analogical negatives adapt more easily to the used techniques, allowing a larger margin of interpretation.

Digital negatives are precisely calibrated on an ensemble of constant variables. They practically function correctly for a certain type of paper, sensitizer, drying, etc… But they give bad results when changing those parameters, even for little changes. The consequence is that digital negatives are useful when a standard for a certain technical paper is established, but while searching and experimenting is easier to use an analogical negative, which better accomodate the variations of the printing technique.

It’s the reason why, even if in general I print using digital negatives or little contacts taken from 120mm negatives, I sometime prepare enlarged negatives. The procedure to obtain it is long and complex, lots of tests are required to learn how to obtain a negative perfectly adapt to a certain print technique.

During the first experiments I produced a series of enlarged unusable negatives, obtained contact printing a RC paper positive. Negatives always had completely transparent shadows and completely opaque lights, caused by the excessive contrast of positives on paper. As ideal negatives for antique techniques are usually thick and with not many transparent parts, those enlarged negatives were clearly unprintable: closed shadows and completely burned high lights, even using long exposition times while printing.

I would have found a way to reduce them and obtain printings from all those otherwise unused negatives.

One day, leafing through the book “The darkroom cookbook” I thought I could have tried some formulas to reduce negatives, to experiment and see if I could use those negatives.

I obviously needed a super-proportional reducer, but a particular formula suddenly stimulated my curiosity: the Eder’s harmonizing reducer. The book said:

This reducer works in a special manner, intensifying shadows and reducing high densities. It is used to correct exceptionally contrasted negatives.

That is, at least on paper, exactly the reducer I was searching for. This formula allows not washing away those little details of the shadows, or better intensifying them, and reducing high lights otherwise impossible to print.

Well, a dream.

Formula and instructions are the following:

Water 750ml

Hydrochloric acid (concentrate) 30ml

Dichromate potassium 10g

Alum 50 g

Water 1l

Completely whiten the negative in this solution and wash until the yellow color is entirely eliminated. Develop in a slow revelator, highly diluted (D-23 1:5 for example), therefore fix and wash.

And here’s a ton of questions that suddenly crowds my mind even before getting ready:

• What does “concentrate” mean?
• Does “Alum” stand for “Potassium alum”?
• Can the operations be carried out in a normal light or in actinic light?
• How can I foretell the right re-development time for each negative?

I couldn’t find any information on line about this reducer, but on www.apug.org forum I was said that I can actually use potassium alum and that muriatic acid has a concentration of 6N, while the hydrochloric arrives to 12N.

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