I've not used Exol in a very long time, but in another thread a new user is going to use a standard acid stop bath. Got me to thinking (a habit I should put a stop to) about why an acid developer needs an acid stop bath. In darkroom 101 1966 we were thought that an acid stop bath stops all the development action of an alkaline developer. What is the Ph of Extol and not just a water stop?
Xtol and stop bath
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- Thread starter Paul Howell
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Xtol pH is 8,2, definitely not acidic.
Xtol uses sodium ascorbate, not even ascorbic acid, and it's got a bunch of sodium sulfite (alkaline) and borax (more alkaline) as well. It's clearly alkaline.
The only (organic) developing agent I know of that works in an acidic solution is amidol. Xtol uses phenidone and ascorbate.
The only (organic) developing agent I know of that works in an acidic solution is amidol. Xtol uses phenidone and ascorbate.
OK, makes sense.
An all-alkaline/neutral processing regimen can make a lot of sense (i.e. running water stop, alkaline fixer) but mostly for water savings during washing (and a hypo-clearing agent isn't required).
Water stop, however, can cause inconsistent development (even unevenness, if you're running a very short process). Every film made in the past century was made with the assumption that an acid step (stop bath or bleach) would follow the development. It does no harm.
There can be advantages to a neutral or slightly alkaline fixer, but there are few if any to eliminating the short acid stop bath. If you don't like the vinegar smell, use citric acid.
There can be advantages to a neutral or slightly alkaline fixer, but there are few if any to eliminating the short acid stop bath. If you don't like the vinegar smell, use citric acid.
I use T4 fix with a water bath stop, no issues with unevenness. I've thought about using old T4 as a stop.
It does no harm, but it complicates the washing step.
I settled to an all-alkaline process about 20 years ago and to date, I haven't noticed any unevenness - but I tend to use developers and dilutions with development times of at least seven minutes, and I develop at 20 degrees pretty religiously.
Whereas I adjust my time for whatever temperature I find the developer at. The A/C is a little overenthusiastic in my darkroom (might need to install a shutter over the exhaust fan to stop it collecting the lion's share of heat as well), so my temperature has been running below 20C, recently as low as 17C. All it costs me is any extra couple minutes tending the tank.
As usual, if you're happy with your results, then carry on.
I presume your concern about the wash step has to do with acid stop and/or fixer contracting the gelatin, making it harder to get the fixer out of it? Worth noting that all the washing instructions we have are also designed around acid stop and acid fix. Including the Ilford wash that lets me wash negatives archivally with just three tanks full of water. Ilford tested those instructions with their own products (films, developers, stop bath, and fixers), and they don't see an alkaline or neutral fixer.
Now, for prints, there could be a significant difference, but there the real problem is getting the fixer residue out of the paper itself -- the emulsion will wash clean in a few minutes, just like RC paper does after minimum fixing in rapid fixer. The rest of the time and effort in washing fiber based prints to archival standards is getting the thiosulfate out of the actual cellulose fibers.
As usual, if you're happy with your results, then carry on.
I presume your concern about the wash step has to do with acid stop and/or fixer contracting the gelatin, making it harder to get the fixer out of it? Worth noting that all the washing instructions we have are also designed around acid stop and acid fix. Including the Ilford wash that lets me wash negatives archivally with just three tanks full of water. Ilford tested those instructions with their own products (films, developers, stop bath, and fixers), and they don't see an alkaline or neutral fixer.
Now, for prints, there could be a significant difference, but there the real problem is getting the fixer residue out of the paper itself -- the emulsion will wash clean in a few minutes, just like RC paper does after minimum fixing in rapid fixer. The rest of the time and effort in washing fiber based prints to archival standards is getting the thiosulfate out of the actual cellulose fibers.
I tend to use a running water wash out of convenience (truthfully I have never tried the Ilford method; it's much water friendlier but it's more work). An all-alkaline process will allow fixation to archival levels in well under five minutes of wash (I do five minutes out of habit). My acid-fix wash regimen was two minutes running water, two minutes hypo clearing agent, ten minutes water. Not terrible, but slower and consuming more water and time.
I also use PMK quite a lot and it gives best stain with an all-alkaline process, but I've converted to all-alkaline for my D-76, HC-110, XTOL and Rodinal work too.
We could probably have an interesting thread talking about proper film washing!
I also use PMK quite a lot and it gives best stain with an all-alkaline process, but I've converted to all-alkaline for my D-76, HC-110, XTOL and Rodinal work too.
We could probably have an interesting thread talking about proper film washing!
MattKing
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A few days of reading there. 
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