Water wise washing.

[Merg Ross]

Merg, how do you keep the water that warm overnight?

Kirk, good question. My typical printing session starts early morning, so at the end of the session I have a six or eight hour head start on the soak process and control over the temperature. I dump periodically through the day and then continue soaking through the night. The night soak starts at 75 degrees and is rarely below 60 degrees by morning (my darkroom is small and well insulated). I have gone as long as 36 hour soaks without adverse effect, but only for convenience not necessity. Soaking is really the key to shortened wash times.

Your earlier post about less use of water and increased charges really hits home here as we enter a drought year. My darkroom wash water bypasses the city sewer and is saved for landscape use. I have become very water conscious in my old age!

[Curt]

I have not found that with one overnight unless the ambient temperature is very warm and thus the holding tray water is very warm.

This has been my experience. Way back in college I'd print late in the evening and leave them soaking after a few changes of water. The next afternoon after school I'd get them onto fiberglass screens. Never had a problem.

[Mark Sawyer]

I had trouble once leaving prints in overnight, (after that I didn't do it again! ). The gelatin was so fragile I couldn't help but damage it.

[Struan Gray]

The best washing strategy is a common homework problem in physical chemistry. Because leaching proceeds with an exponential decay, for any given total amount of water and time, washing with two lots of half the water for half the time each removes more of the leachant than using all the water in one long soak.

Running water is what you get when you take this to its logical conclusion, but there is a gotcha. The leachant has to have time to diffuse into the clean water, and for thiosulphate complexes coming out of paper, the diffusion is so slow that you waste most of the water. In this case, a few cycles of fill, static soak and dump work just as well, and use far less water. Some people I've known even re-used the intermediate baths, making the second the new first, and so on. Residual silver testing is a little more difficult now that so many 'common' chemicals have disappeared from photo stores and local drugstores, but it can still be done to check that the wash is thorough enough.

The only gotcha with the fill-soak-dump method is that you should take care to avoid carry-over between baths. Fully empty the tray if you are going to dump and refill, or allow the surface water to run off the print as much as patience allows if moving prints between baths. Advanced physical chemistry students get to calculate how a relatively small amount of carry over can quite dramatically compromise the efficiency of the overall wash.

[BetterSense]

The best washing strategy is a common homework problem in physical chemistry. Because leaching proceeds with an exponential decay, for any given total amount of water and time, washing with two lots of half the water for half the time each removes more of the leachant than using all the water in one long soak.

Running water is what you get when you take this to its logical conclusion, but there is a gotcha. The leachant has to have time to diffuse into the clean water, and for thiosulphate complexes coming out of paper, the diffusion is so slow that you waste most of the water. In this case, a few cycles of fill, static soak and dump work just as well, and use far less water. Some people I've known even re-used the intermediate baths, making the second the new first, and so on. Residual silver testing is a little more difficult now that so many 'common' chemicals have disappeared from photo stores and local drugstores, but it can still be done to check that the wash is thorough enough.

The only gotcha with the fill-soak-dump method is that you should take care to avoid carry-over between baths. Fully empty the tray if you are going to dump and refill, or allow the surface water to run off the print as much as patience allows if moving prints between baths. Advanced physical chemistry students get to calculate how a relatively small amount of carry over can quite dramatically compromise the efficiency of the overall wash.

I will differ on several points. Note that most of my experience is with washing acids and bases off of semiconductor wafers in ultrapure water. This is typically monitored with a resistivity monitor.

Running water is not the "logical conclusion" you say it is, in fact it's the opposite. It is NOT better than repeated dumps, unless perhaps you have perfect laminar flow in your tank, so that incoming water does not mix with existing water in the tank. It should be intuitively obvious that this never happens, as the incoming water always mixes together with water in the tank, even in million-dollar computer-designed wash tanks. This means that running water is actually the worst of both worlds...extreme amounts of "carry over", with extreme amounts of water usage. You can test this yourself with a resistivity meter* and this has been done many times in the semiconductor industry. Repeated dumps are not "almost as good as" running water, they are "better than" running water. Overflow rinsing is still used DESPITE it's inferiority, because depending on the surface state of the wafers and relative cleanliness of the water vs. the air, exposing the wafers to air can be a Bad Thing. But it's never done because it's better at rinsing. Dumping is better. Actually, best of all from a washing perspective is initial washdown spray rinsing, followed by dump rinsing, but spray rinsing is even worse than dump rinsing for contamination from airborn particles (particles too small to be visible, even with an optical microscope).

Carryover isn't as huge of a deal as you make it sound. It makes a big difference compared to no carry over whatsoever, but it takes extreme amounts of carryover to make dump rinsing as bad as overflow rinsing.

I'm not going to attack the issue of how long prints need to be in clean water for all the hypo to diffuse out of the emulsion/print. People like to talk about this a lot but I have never once seen a figure for the diffusion coefficient of hypo in gelatin or cotton. Actual data would be neat.

*To test it for print washing, try this: put 1 teaspoon of food coloring in your print washer and mix well. Turn on the water. Write down how long it takes for the food coloring to disappear. Unless you have a perfect laminar flow washer, it will be a while, because the food coloring will mix with the incoming clean water. Next, repeat the test with dump rinsing. Put 1 teaspoon of food coloring in your print washer, mix it up, and dump it all out, and fill it back up. Repeat. Or rather, don't bother to repeat, because you probably won't see any food coloring...you dumped it all out.

[Struan Gray]

I've washed wafers too. Well enough to see the one, single impurity atom in a square micron with my UHV STM. My respectful opinion is that the perfectionism I developed for that wasn't much use when it came to washing fixing complexes out of photographic paper. The timescales and processes by which the contaminants are removed are too different.

Everyone is free to develop their own wash routines. Residual silver tests are not hard.

[Larry Gebhardt]

I rinse with running water for about a minute in a tray, then transfer to the archival washer. When I'm cleaning up for the night I run the washer at a medium flow to change out the water (about 10 to 15 minutes) and then let it sit over night. In the morning I remove the prints. The residual fixer tests show this works well (at least in my darkroom).

I missed a print in the washer one day, and left the washer full since I thought I would be back to it that evening. When I came back a few days later the emulsion had slid off the paper and made a huge sticky mess in the washer. But I haven't had an issue with leaving them over night.

[Jim Jones]

. . . Some people I've known even re-used the intermediate baths, making the second the new first, and so on. . . .

I've done this for decades. When producing many 8x10 RC prints in a hurry, washing about 30 prints in three 5" deep trays with agitation worked well. This used a very few ounces of water per print. Leftover prints from 40 years ago are still good.

[ROL]

[COLOR="#808080"]

WHAT IS THE ILFORD PHOTO ARCHIVAL SEQUENCE?

"The ILFORD PHOTO Archival Sequence is a method of processing fiber base papers for maximum longevity... While reducing the amount of water and time used.

The method, which was fully tested more than a decade ago, requires the use of a non-hardening rapid fixer mixed at film strength.

After the paper has been developed and stopped, it is placed in such a fixer for 60 seconds with intermittent agitation.

Next the paper is placed in a running wash for five minutes, followed by an immersion in ILFORD PHOTO Wash Aid (1+4) for ten minutes with intermittent agitation.

The end of the sequence requires an additional five minute running wash."

Yeah, I remember coming across this occasionally in the past. I always thought of it as some kind of advertising scheme for the Ilford wash aid, even though I know that just can't be true, because of the unreferenced testing for what amounts to 25% of the time for 'normal' constant flow washing.


To summarize thus far? (correct me if I'm wrong):

1. rapid fix
2. wash aid/hypo eliminator
3. constant flow, as opposed to fill and dump
4. reduce normal time as much as you dare!
5. results depend on paper type*

As regards the prevention of leaching the whites from a paper, I still see no real conclusion here (though that seems to be Ilford's contention – perhaps(?) only having to do with their papers), and have experienced no perceptible differences myself.

FWIW, my mural prints are washed in a homemade 'flat washer' since they cannot be washed in my largest commercial washers (and I'm not rich). Even though they receive constant water flow, I manually dump the water many times throughout the wash, and shuffle prints, which can 'stick' together, the topmost otherwise becoming 'dry' during the wash. I wash as long as 1½ hours or more on occasion to have any reasonable expectation of a normal wash. Never a problem with results (my back, yes), so far.

* I've had Kentmere Fineprint emulsion dissolve in the developer, and no problem with Oriental swimming overnight.

[Doremus Scudder]

...

To summarize thus far? (correct me if I'm wrong):

1. rapid fix
2. wash aid/hypo eliminator
3. constant flow, as opposed to fill and dump
4. reduce normal time as much as you dare!
5. results depend on paper type*

As regards the prevention of leaching the whites from a paper, I still see no real conclusion here (though that seems to be Ilford's contention – perhaps(?) only having to do with their papers), and have experienced no perceptible differences myself. ...

Hi Ben,

Just to prevent confusion: Hypo Clear aka Kodak Hypo Clearing Agent is basically the same as Ilford Wash Aid and other sodium-sulfite-based wash aids. Hypo Eliminator was a Kodak product/formula based on hydrogen peroxide and its use is no longer recommended!

As for this whole discussion on washing, everyone should take a look at Les McClean's article "Mysteries of the Vortex" available here
http://www.film-and-darkroom-user.or...read.php?t=296
as well as the discussion of washing in Ctien's "Post Exposure," which is available for pdf download for free somewhere on the Internet.

The whole question of optimizing water use for print washing, I think, misses an important point. Yes, we can, through testing and trying different schemes, come up with a washing method that uses the least amount of water for the least amount of time. However, by optimizing these variables, we are eliminating any kind of safety margin we might have and risk under-washing the prints unless stringent quality control is used.

I prefer to err on the side of "guaranteed adequate wash" and use a bit more water plus a bit more time than my residual hypo test tells me is necessary for a good wash.

FWIW, I find it only logical what BetterSense maintains above, that a constant running water wash without dumping is actually less efficient. Plus, since leaching is the principal mechanism for washing after the intial carried-over fixer is rinsed off, I see no reason for massive water flow.

I use a combination of minimum water flow and fill-and-dump. My washers have been modified (actually just added a sprayer set-up made from perforated tubing) to spray water onto the water surface in the washer, which then drains from the bottom of the washer. The flow is very low. Then, at roughly 20-minute intervals, I drain the washer tank and refill it. This is my largest use of water, since the tanks do hold a bit. At the end of an hour, I have emptied and refilled the tank twice, and there has been a slow water flow for the rest of the time. I then pull a print and test it for residual hypo. If it's fine, I put it back in and let it sit for at least another 20-30 minutes with the minimum flow (part of this is to leach out the brighteners - more later).

I realize water is a precious resource and am as conservative as I can be using water. On the other hand, I'm not about to cut corners on print washing any more than I would on fixer freshness, etc.

As to optical brighteners: I thought I had a chart somewhere showing the leaching of optical brighteners in paper over time, but couldn't find it. At any rate, IIRC, the bulk of the brighteners, ca. 70+%, are removed after about an hour in the wash anyway; after two hours there is practically nothing left in the print in the way of brighteners. For prints that are displayed, the rest of the brighteners bleach out after a period of exposure to light, from what I understand, although the by-products are left in the emulsion.

I, for one, dislike brighteners for a couple of reasons. First, I think they make the whites look fake. I like the look of the paper base and the baryta coating just the way it is; I don't need it to fluoresce. I have always liked the look of the whites in the prints that have been in the washer longer than the work prints I use that have really just been given a cursory wash. And, I always liked the whites better under incandescent lighting (no UV = no fluorescence of brighteners) than in sunlight...

Second, have you ever seen a white shirt that has been sitting in the closet, washed but unworn, for a few months? It turns yellow because the brighteners degrade. If they use those kind of optical brighteners in paper, I don't want any, thanks. I know Bruce Barnbaum and Les McLean both advocate leaching out the brighteners. Many papers are made without them. Any paper made before about 1953 didn't have them; I don't see a lot of people complaining about the whites in Weston and Adams and Cunningham et al. prints from before then

Best,

Doremus