Pyro stain problem

[The Stone]

Hello,

I have been using PMK Pyro to develop my sheet film for salt printing, most of the time it works well but sometimes there is too much general stain leading to a very flat print and long exposure times.

I've got one negative with this problem that I really like and I was wondering if anyone knows how to reduce the pyro stain, I am sure it will print better without.

Thanks for your advice

Ben

 

[gzinsel]

I do not know if this true. . . .. But I seem to remember or I thought I have read before that an acetic stop bath reduces stain. I use pyrocat HD. I seem to remember reading something about not to use the acidic stop bath for it reduces stain. But that just might be for that dev. only. Also I might suggest other possibilities. unbeknownst to you, did the film get fogged? leaving a general "over-exposure" that will lead to reduced contrast and higher fog levels. if your shadows are (more dense) higher than normal, I would suggest you either over exposed or if your B+f (at the edge of film) is higher than your film got fogged. If you have no "real" good shadows i.e. a high key image, i would suggest looking at other negs which would have a proportional time of exposure and review items together. But to answer your original question . . . I do not know for sure"

 

[MDR]

What light source are you using? Removing the stain after having developed the film is not really possible. Changing the lightsource to something that gives more contrast and might help. Amount of contrast: Light Shade > direct sunlight > artificical UV lightsource. Double coating instead of triple or single coating is another way to get more contrast. Of course you could also make a copy neg of the neg you like and develop it in a non-staining developer (will result in a slight loss of detail). A weaker salting solution is also a good way to increase contrast 1.5 instead of 2%. Another more toxic way to increase the contrast is the use of potassium dichromate.

From Christopher James Book of Alternative Processes:
"One of the easiest methods of affecting the contrast of your salted paper print is
to alter the initial wash-development bath. To increase the contrast, as well as to change
the color of the image to a reddish brown, simply add 3 – 5 drops of a 10% potassium
dichromate solution (100 g potassium dichromate to a liter of distilled water
) to 1000 ml of distilled water. Then heat this solution in a microwave oven in a plastic beaker or
use a double boiler like tray set-up. The warmer the solution, the stronger the change to
contrast and color and the less likely you will experience salted paper speckling.
You can also increase the contrast of your print by adding a drop or two of a 1% to
5% solution of potassium dichromate solution to every 28 ml of the sensitizer. This will
also result in a color change to reddish brown that is similar to the gold / borax toner
described later. (A 5% solution is made by dissolving 5 g of potassium dichromate in
100 ml of distilled water.) "

If this doesn't work you might use a Hybrid process (digital negative scan from your neg) and increase the contrast digitally but this should only be used as a last resort.

Good luck

 

[Doremus Scudder]

A couple of suggestions here from my own personal experience with PMK.

First, yes, you can remove the stain. I found that when trying to intensify a PMK-developed negative with Kodak Rapid Selenium Toner diluted 1+2 that the stain disappeared almost entirely. This reduces the contrast of the negative by about the same amount as the KRST adds, so the result is a wash, without the general stain, however. In your case, this may give you a bit more shadow detail, but no real extra contrast anywhere else. Give it a try if you think just getting more shadow contrast will solve your problems.

A strongish sodium sulfite solution is also supposed to remove the stain. I haven't tried it, but it is the reason stated for not using hypo-clearing agents with PMK. You might try that.

When I need more contrast in a neg, I usually use the bleach/redevelop method. Everything can and should be carried out in normal room light.
Step 1: bleach the negative in a rehalogenating bleach of potassium ferricyanide and potassium bromide (15g potassium ferricyanide, 15g potassium bromide,1 liter of water). Treat the negative till the silver image is completely gone. The bleach rehalogenates the silver image, making it invisible, but leaves the stain image untouched, which you will see as a faint yellow image.
Step 2: wash the negative in running water for five minutes.
Step 3: redevelop in a staining developer (e.g., PMK, which is what I use). Use your normal development time and agitation scheme. Don't worry about developing too long, your goal is to redevelop all the rehalogenated silver. This step restores the silver image and gives you another stain image on top of the one already there, thus increasing contrast. This works quite well and is easy to do.

Some say you can repeat this procedure once if more contrast is needed. I have never tried.

If you are getting too much general staining with PMK, you are using it wrongly, either too much agitation (are you rotary processing? If so, use Rollo Pyro), too much time with the negative "in the air" and not in the solution (aerial oxidation) or too much time elapsed after mixing and before developing. Also, the "after-bath" in the spent developer originally advocated by Gorden Hutchings is not necessary and only leads to more overall stain. Eliminating this step will reduce general stain. I tray develop and get very low levels of general fog. Refine your technique a bit and you can likely eliminate this problem.

Best,

Doremus