al olson
17-May-2011, 17:50
Years ago when I bought my DoMac processor there was a company that supplied chemicals that were specially designed for it, both for black and white and for color.
For those who are not acquainted with the DoMac I will explain briefly how it operates. The processor has two troughs to pass the paper through the developer and the fixer or the blix. There are three sets of powered rollers, one pair to push the paper into the developer, another pair to pull the paper from the developer and push it into the blix, and the last pair to pull the paper from the blix.
In each trough there are acrylic tubes (idlers if you may) to hold the paper down in the solution. The troughs are temperature controlled at 98 degrees and the speed is designed so that the paper is exposed to the solutions for the prescribed time, approximately 45 seconds. All of this was working very well while I was using their chemicals. Even the b&w developer was used at 98 degrees.
Now I can no longer get the special chemicals. It turns out that most RA-4 chemicals work with no problem. The problem is using b&w chemicals. For convenience I would like to use this processor for b&w again.
I have been using Dektol and am finding that after processing a few sheets there begins to develop a brown stain, more or less in a line across the width of the paper. The stain appears to be transfered from the idler rollers in the developer. It seems to form where the surface of the solution makes contact at the roller while it is still.
From readings of photo chemistry in the '50s I recall that when hydroquinone oxidized it formed a brown aniline dye which accounted for the stain that we would get on our fingers. I assume that is happening here, amplified by the higher temperature.
So the questions are:
1. Are there any additives that I can use to inhibit the oxidation of Dektol. I have tried as much as 3 teaspoons of sodium sulfite with no results.
2. Can you recommend an alternative print developer that doesn't stain. I have checked Steve Anchell's Darkroom Cookbook, but not found anything that looks feasible.
An alternative is to use the processor at room temperature (I have not tried that yet), but I am concerned that 45 seconds in the developer may be a little short. I currently use 90 seconds when I tray develop and that gives me the results that I prefer. I also make final 16x20 prints with the Jobo using the same development times. I would not like to be using longer exposure times to accommodate a shorter development time, but keep the processes consistent.
Your help is appreciated.
For those who are not acquainted with the DoMac I will explain briefly how it operates. The processor has two troughs to pass the paper through the developer and the fixer or the blix. There are three sets of powered rollers, one pair to push the paper into the developer, another pair to pull the paper from the developer and push it into the blix, and the last pair to pull the paper from the blix.
In each trough there are acrylic tubes (idlers if you may) to hold the paper down in the solution. The troughs are temperature controlled at 98 degrees and the speed is designed so that the paper is exposed to the solutions for the prescribed time, approximately 45 seconds. All of this was working very well while I was using their chemicals. Even the b&w developer was used at 98 degrees.
Now I can no longer get the special chemicals. It turns out that most RA-4 chemicals work with no problem. The problem is using b&w chemicals. For convenience I would like to use this processor for b&w again.
I have been using Dektol and am finding that after processing a few sheets there begins to develop a brown stain, more or less in a line across the width of the paper. The stain appears to be transfered from the idler rollers in the developer. It seems to form where the surface of the solution makes contact at the roller while it is still.
From readings of photo chemistry in the '50s I recall that when hydroquinone oxidized it formed a brown aniline dye which accounted for the stain that we would get on our fingers. I assume that is happening here, amplified by the higher temperature.
So the questions are:
1. Are there any additives that I can use to inhibit the oxidation of Dektol. I have tried as much as 3 teaspoons of sodium sulfite with no results.
2. Can you recommend an alternative print developer that doesn't stain. I have checked Steve Anchell's Darkroom Cookbook, but not found anything that looks feasible.
An alternative is to use the processor at room temperature (I have not tried that yet), but I am concerned that 45 seconds in the developer may be a little short. I currently use 90 seconds when I tray develop and that gives me the results that I prefer. I also make final 16x20 prints with the Jobo using the same development times. I would not like to be using longer exposure times to accommodate a shorter development time, but keep the processes consistent.
Your help is appreciated.