RA4 STOP BATH QUESTION
Can a regular acetic stop bath ever be sufficient, given that it is changed frequently?
Why is sodium sulfite recommended to be added to the acetic bath? Doesn't the acid and water, alone, remove the developer efficiently.
I do something rather unorthodox: after the stop bath I fix and turn lights on to view the print. Sometimes I let it go at that. Sometimes I do want the slight increase in warmth so I will then, in full light, bleach (potassium ferricyanide) for a minute, and then for a few seconds, I fix again in the same fixer. I think that that is a much more rational way to go about this process. I do the same fix/bleach reversal with film. Why does everybody else bleach before fixation?
Another question (will reflect my chemical naivity) : if one bleaches (color paper or film) in full roomlight is there a danger of (is it called) halogenation with the silver salts being made sensitive to light? Thanks for all the information you are able to impart. - David Lyga.
I use 1% to 2% Acetic Acid as the stop bath for RA4. I have also used Kodak Indicator Stop. Both work just fine.
If you leave out the Sulfite from the Acetic Acid, then the Stop becomes an indicator bath turning cherry red when it becomes exhausted. Adding Sulfite will NOT regenerate it but will decolorize it thereby giving you no notice of exhaustion.
If you bleach in most Ferri bleaches, you rehalogenize the Silver as it oxidizes and this Silver salt is light sensitive. As for using a fix, it depends on the fix. The fix baths used for color processes are selected to prevent shifts in dye hue due to pH. Also, just fixing makes a print darker and less saturated and therefore harder to evaluate.
Thank you PE. Letting it go at simply fixation does give a rather subdued color (even Hollywood did this a few times with their films). Some scenes might benefit. It is a bit darker but you can always expose a bit less. You do scare me when you confirm that the silver, once again, begins to be light sensitive. Does that mean potential light fog? Is it best to bleach in darkness and fix again before turning on the lights? As you can see my chemisty knowedge is competition for MIT. - David Lyga
So that's why my stop bath turned cherry red, thanks! I knew to chuck it out anyways but did wonder!!!
I do my RA-4 in full darkness until it is fully fixed. Haven't dared to try my amber safelight yet.
If you fix and do not bleach, there is nothing light sensitive present, but if you bleach with no following fix, there are light sensitive materials that can darken. If you fix, bleach and then wash and dry, you still have light sensitive materials present. This is only if you use a Ferri bleach.
I use 2 safelights all the time. One pointed at the ceiling and one pointed away from the enlarger and both at about 5 feet. No fog ever!
OK, I'll have to try it. What is there to lose but a sheet of paper I guess though the fact sheets all seem to say complete darkness is best or it will fog.
I use a color safe light occasionally.
I cant notice fog.
Kodak paper is built to allow a WR-13 series safelight.
here's the quote from the Portra/Supra tech pub:
Using a safelight will affect your results. If absolutely
necessary, you can use a safelight equipped with a KODAK
13 Safelight Filter (amber) with a 7 1/2-watt bulb. Keep the
safelight at least 1.2 metres (4 feet) from the paper. Keep
safelight exposure as short as possible. Run tests to
determine that safelight use gives acceptable results for
That's what sent me scurrying into the dark... and actually I found it wasn't that hard to do really. I only messed up one page before learning how to ensure the paper is fully in the tray and covered by liquid.