dupont 4-r, eder's harmonizing reducer

Hello,
during the last days I prepared some enlarged negatives (adox film and hc 110 developper) for van dyke brown prints using rc paper positives. It takes me some times to find the right amount of exposure, developping time and paper positive caracteristics. Negative higlights were too transparent and -thinking I was underexposing the enlarged negative- I tried several long exposures, just to discover that the problem was a too hard paper positive.
Now I have several film sheets that are too contrasty, even for vdb prints. They have transparent highlights with minimum detail and dense shadows. I know that the best is to produce correct enlarged negatives, but I want to play a little bit with these odd negatives. I was thinking to use some super proportional reducer, but I'm afraid to loose the small amount of detail I have in the negative highlights. In the darkroom cookbook there is a formula of the "dupont 4-r, eder's harmonizing reducer" that intensifies lighter densities and reduces heavier densites, exactly what I am looking for.
I searched the web and this forum but I can not find a lot of informations. Does anyone here have ever used it?
Do you have any suggestion? Especially about redevelopping time?
Do you have an idea of the correct concentration of hydrochloric acid (the book just says "concentrate")?
"Alum" means the well known "potassium alum"?
Thank you very much for your help
Fabiano

Dupont 4-R, Eder's Harmonizing Reducer
This reducer intensifies lighter densities while reducing heavier densities. Used to correct excessive contrast.

Water 750 ml
Hydrochloric acid (conc) 30 ml
Potassium dichromate 10 g
Alum 50 g
WTM 1 l

Bleach negative to completion in the above solution. Wash until all the yellow stain is removed. (This process can be shortened by rinsing for 2 to 3 minutes and then treating with a 2% solution of sodium bisulfite for a few minutes, and then washing.) Redevelop in a slow-acting, dilute developer (such as D-23 1:5), then fix and wash.

nworth,
thank you for your replay. I own the darkroom cookbook but I would like to know if anyone tried this formula and has some suggestion.
Concerning redevelopping I think I will cut one film sheet and try different time to find which one gives me the correct density.
I'm still not sure if "alum" means "potassium alum" that I have or some other thing (I'm sorry for my english...). I'm also not sure what is the exact meaning of "concentrate" hydrochloric acid.
Thank you very much
Fabiano

The alum is almost certainly potassium alum, and I doubt if the concentration is particularly critical. It looks like it is a hardener here. Concentrated hydrochloric acid is about a 12N solution. Muriatic acid, which is readily available as a concrete cleaner, is usually about 6N, half the strength of the concentrated acid. I haven't tried this formula, and I suspect it may not work well with modern emulsions. In any case, it will probably work differently with different emulsions. You should definitely try it on some test negatives that don't count before you commit your good ones. Choose test negatives on the same film and with the same processing as the targets. You have some extra controls here with the degree of bleaching and the choice of redeveloper. A developer with a lower sulfite content, like Rodinal, may be a better choice than D-23. You might also investigate one of the more common subproportional reducers. In general, I have found that desperate measures, such as marked reduction or intensification, can not save a negative to give a really good print, although they may make an unprintable negative just about printable.

I would make a contrast-reducing mask rather than messing with reducer.

hello,
I finally played a little bit with the reducer. here you have some note, I hope it can be usefull for someone who want to test the eder's harmonizer reducer:

* I founded some hidrocloridric acid at 1N. I did not had with the suggestion of nworth about concentration and I used it directly. When I used only 30ml the solution did not bleached the film. After that I added 300ml of acid and the bleach took place after 1 to 4 minutes.
Now reading that concentrated acid means 12N it makes sense that the solution worked well with 300ml of acid instead 30ml. The final concentration is almost the same you obtain mixing 30ml at 12N.

* I could not notice the yellow dicromate stain described in the book. The bleached negatives are light green-gray, and they do not change their color even after 1h in running water.

* I redeveloped using perceptol 1+4. I tried to guess the time with visual inspection, and I founded something between 2 and 5 minutes.

* The contrast is heavly reduced and lighter densities are intensified as it is said in the darkroom cookbook. I did not really belived that it works but now I have seen it with my eyes.

* The negatives printed fine on cyanotype. It is not easy to guess the redevelopping time and each negative is different from the others. You have to adjust the cyanotype printing time, but negatives that printed with washed highlights after 40 minutes of exposure now print correctly in only 12 minutes. There is some shouldering in the highlights, but it works well with certain images. I'm printing a series of what remains of the Berlin wall, and the cyanotype prints really fit my taste. I'm really happy with it. I reduced also a portrait and I'm not happy with the result. It really depends of the image, the negative, etc.

The only problem is that I have a lot of uneven stain, strange straight lines that appears in the negative, etc. It is difficult to describe, Sorry for my english. I'm not sure what is the problem here. I bleached and redeveloped with constant agitation but it does not change. When you have negatives with a lot of details you can not notice it, but when you have flat surfaces it is really disturbing. This is the only problem for me.

You end with a lot of gray staining in the redevelopping tray, but it is not too difficult to clean it.

**************

Ok, to conclude I'm quite happy with the results. It is sure that is better to obtain perfect negatives, but now I can perfectly print some impossible negative.
And I had a lot of fun today.
In any case I'll search something about contrast-reducing mask, as suggested by psvensson, but I have no idea where I have to start.
Thank you very much for you suggestions
Fabiano