Archival print washer types

Seems obvious to me that emptying and refilling dilutes more than using the same amount of water to gradually dilute the old water. And isn't low concentration of fix in the water the goal? The other thing is agitation, but a recirculating pump should be easily providing enough of that.

There has been plenty of testing done in this respect. Aggressive agitation can be counterproductive. Just like smoke tests can be used to determine the efficiency of a fume hood, likewise dye tests can reveal the efficiency of washers.
Yes, soak and drain, soak and drain repeatedly, is one strategy to conserve water, at least if the tank or tray size is relatively small. But slot washers can conserve even more water if well designed, and certainly need less attention when at work.

I have always thought that hypo is basically heavier than water and will naturally drop to the bottom therefore go away with slow circulation. I have also heard
dumping the water completely and refilling is a very good way of washing prints.

Carnie Bob said:

I have always thought that hypo is basically heavier than water and will naturally drop to the bottom therefore go away with slow circulation.

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Legacy of Fred Picker

(...) Sounds perfectly reasonable. People believed it. In fact, people believed it so strongly that it became an article of faith…despite the fact that it’s wrong.
Fixer is heavier than water, all right, but fixer being washed out of a print goes into solution with the water and doesn’t separate back out again. Especially in the turbulence of a typical print washer, this happens nearly instantly. And irreversibly. (...)

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no, the idea that hypo sinks to the bottom because it's heavier than water is a relic of Fred Picker's attempt to reinvent physics. fixer is soluble in water; it will leave by whatever route the water leaves.

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And yes we all know that some solutions separate over time But the reasoning here is wrong, separation happens in solutions that have ingredients in suspension, not dissolved.
(...)
You can try putting a totally soluble dye into water, it'll be heavier and initially may drop but if you leave it the solution will become uniform, in the case of hypo we agitate to help this diffusion happen

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Several important points have been totally overlooked so far. Slot washers can be designed which siphon off the bottom,
and then up and out of a top drain port, as well as potentially allowing for some removal directly from the bottom and the top. That's why dye tests are important, to understand the real circulation as well as the ideal flow rate. In a competent system, ALL of the test dye will exit in a predictable and fairly quick manner; none will accumulate at the bottom or be left in suspension. Yet a good washer design will not be water wasteful either.

But aggressive water input might create a laminar flow effect which presses the paper against the septums, or otherwise actually hinders a steady soaking out of the hypo. Repetitive fill and drain cycles might work OK, but will require a lot more water if a quantity of moderatley large prints is involved.

Then there's the problem of the septums themselves, and if there are just too many of them in there holding the paper too tightly. Mine are all dimpled so that the paper can't stick to the plastic; water easily flows around both the front and back of the print, and that also keeps the prints suspended between their septums, rather than sticking to them.

You should do dye tests with the Kodak tray siphon too. When the amount of water flow is correct in relation to the tray size, there will be a steady circular flow in the tray from the device and then back into its outlet component. These work well, but cannot handle a quantity of prints efficiently, and consume quite a bit of water.

In many parts of the world, water is increasingly becoming a precious commodity requiring thoughtful use. And where it is scarce, it's also more likely to have greater mineral content as well as added chlorine. Those can be filtered out; but good filters aren't cheap, and need to be frequently replaced.

One of the features of the Kodak tray siphon is that it provides a circulating flow that is designed to help ensure that if you wash several prints in the same tray at the same time, the flow keeps them from sticking to each other. That is a primary reason that the water use for the tray siphon is higher than with a slot washer which relies instead on the slots to keep the prints separated.
Diffusion is an important component of a good wash - fixer and development/fixation byproducts need some time in contact with water to diffuse out of paper. For that reason, there is a point where increasing the flow of water doesn't meaningfully increase the rate that those unwanted elements diffuse from the paper. The trick is to use just the right amount of water, flowing at the minimum speed that fully does the job. The design of the washer factors in to what amounts and what rate those are.

Great discussion!

One should be testing prints for retained fixer, not the washer.

ic-racer said:

One should be testing prints for retained fixer, not the washer.

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There's some good advice! Selenium toner or the silver nitrate test solution.

You should do both. But when designing a washer it's very important to dye test it. Likewise in relation to the correct volume of water flow. Telling people to skip a simple and extremely practical dye test is quite misleading.

I did my prototype design just 11X14 capacity, and when that dye-tested well and actually proved quite efficient, I scaled up to 16X20 and 20X24 units too. Selenium toning wouldn't tell me a thing, because that works perfectly right after the holding tray of water, even before the final washer itself (I use TF4 and TF5 fixer).

Even with an old-time Kodak tray siphon, you can quickly identify things about water-flow efficiency using dye which would take an awful lot of post-testing to properly sort out. I recall one well known fine art photographer who had to make twice the number of prints each session as he really needed because he liked using single-weight paper, and half of them ended up getting damaged in too aggressive of a washer.

I drilled a few holes in the bottom of a ribbed plastic tray and just let water flow in and out beneath the print/s.

I use that bottom hole tray concept for an oversized 30X40 inch print washer, but in conjunction with the Kodak tray siphon too. Just one big print at a time. The key is holes just the right size, and not too big, and properly spaced.

I use two trays, each with a pattern of holes on the end.
The top tray flows into the bottom tray. A trickle of water flows into the top tray - just enough to keep the water level practical there.
The print goes into the bottom tray - sometimes with others - for the first half of the wash. It finishes its wash in the top tray, by itself.

So you might call that a cascade system, Matt? Interesting.

An older version, with flow increased for the purpose of display:

I've since replaced the larger round washer with a duplicate of the top, black, 11x14 washing tray.