technical question re: washing paper for 1 hr vs. volume of water

Ok, so let's say hypothetically ....
we have a 5 gallon tank of water on one shelf (I don't know how much water the Cachet 11x14 tank holds), the shelf below it there is a Cachet 11x14 archival wash tank with a given number of slots for 12 prints, and a third, empty holding tank of 5 gallons below so gravity takes the water through three tanks. The water naturally flows down hill from the above tank through the archival tank into the waste water tank. I'm sure one of the variables is the diameter of the tubes. However, would a 5 gallon tank of water (or whatever volume is necessary) be equivalent to 1 hour's worth of washing? Or, perhaps the question should be; what volume of water is needed to rig this up so you have a washing of 1 hour. (I just remembered another variable lets just say all prints would be inserted at the same time to cut down on any extra variables).

the reason I ask is that I'm trying to build a darkroom with no running water and no drain in someone else's house so it would be portable, and the main concern is the washing of the prints. they also use a spring and a septic system.

any ideas on this? I've seen portable darkrooms such as the one Bill Schwab uses and am wondering if this could be modified to accommodate regular silver printing.

thanks...

Dorothy

according to Cachet (B&H) the Cachet runs 26 oz per min which is equivalent to 12 gallons per hour (1560 ozs per hr). Is this correct?

where there's a will there's a way...

It doesn't answer your question but I am in the same situation - no running water in darkroom. So I just set up my slotted archival washer right outside of my garage and feed it from outside water supply. Because it takes so long to carefully print each and every exposure, and I don't process volume, this setup has never caused an issue. I just transport a wet print from darkroom to outside in an empty tray. I could really set this up in bathroom or shower, but I haven't.

If you use HCA, the washing time is reduced to 1/2 hour, also.

I looked it up for you.

In a book "Way Beyond Monochrome" second edition, page 45, there is a chart that shows at 60 minutes mark, the left over Thiosulfate reaches acceptable level for archival storage. On next page, it says that "The flow of water only needs to be sufficient to replace the entire volume of water every 5 to 8 minutes" It further says "Increasing the flow of water does not speed up..."

So you can now calculate your water requirement IF you know the capacity of the washer itself.

I believe Cachet washers are of the diffusion category (mine is), as opposed to active jet style, which are simply an automated form of the basic "fill and dump" model (preferred) of washing. Fill and dump, tray style, requires a certain number of complete changes of water for each period of diffusion. The GOOD BOOK (AA's The Print) specifies 12 changes @ 5 minutes each = 1 hour. There would be 12 vertical "trays", one slot for each print, in the typical gravity style washer.

So, if I understand the hypo(thetical) correctly, figure the volume of each slot (tray) X 12 complete changes + the total volume of the washer to start the process.

tkamiya said:

If you use HCA, the washing time is reduced to 1/2 hour, also.

Click to expand...

As I understand it, Ilford would say that with washaid(HCA) washing time can be reduced to a lot less than 1/2 hour.

I haven't done the calculations but it seem that the OP set up runs water through at a much more and thus wasteful rate.

pentaxuser

there used to be a kit to convert a standard fish tank to a print washer, sold by fine art photo supply
their old website is here -------- >>> http://web.archive.org/web/20021126080725/http://www.fineartphotosupply.com/printwasherpage.htm
it is a fish tank, some plastic pipe with slots cut into it,
and sheets of plastic to fit into the slots and segregate the prints.
soaking the prints leaches the fix out of the paper.
soaking, draining the water, soaking again, draining the water a handful of times
from what i have read ( and using a fixer remover ) is the best way to wash prints.
you don't need runningwater, and you onlyneed as much water on hand to fill and drain
your fish tank, and time to wash the prints ...

first of all, thank you all for your quick responses. alot of good information here. because we are using a spring for our water supply, I don't want to dump any chemicals in the ground. there is no 'gray water' tank here, it all goes to the same place in the septic system. I thought if I knew how many gallons I could just collect the used water and then dump it somewhere else. I know that you can do that with film by using Ilford's 5-10-20-25 method. Perhaps using one of the roller tanks for paper might work?

As a rough measure of my own water flow rate for my 12x16 6 slot washer (@ 8 gallons an hour) and from the calculations from 2 of the best sources mentioned above, I suspect that you will need a minimum of 2x5 gallon containers to meet a satisfactory level of washing for 12 prints in an hour.
I also use alkaline fixer which requires less wash time than acid fixer and may be worth considering if you don't have space for an extra tray for HCA for reducing wash time with acid fixer.
Regards, Mark Walker

I believe that one of the nice things about the metric system is that volume and length measurements are related.
If true - then measure the inside dimensions of your washer in centimeters. Then multiply the length x width x height, for the total cubic centimeters. From this you can convert to gallons, etc.

1000 cc (cubic centimeters) = just over a quart.
You can determine the flow rate by dividing the 5 to 8 minutes (maybe pick 6 minutes to start), into the total volume, for how much per minute.

Somebody please confirm this relationship.

Also, one of the chem engineer folks, like Photo Engineer, might be able to tell you the best fixer to use, in terms of environmental friendliness. The alkaline, or more neutral fixers, like TF4 or TF5 might take less time to wash out.

Like the OP, I'm on well and septic bed, as well as having a "dry" darkroom. I've often pondered the idea of a recirculating wash system, with a small flow pump, and using a glass-and-carbon filter, similar to an aquarium setup.

If the carbon (charcoal) filter can absorb the residual fixer and other chems, a small amount of water could serve the purpose, but I have no idea whether charcoal would work, not, if it does, for what amount. Hoping not to deflect from the OP's idea or thread here, and I apologize if I'm having that effect. Please let me know.

There are ion exchange bead bed filters that are used by 'washless' commercial photo processors machines to deal with their taank overflow fliuds disposal.

They filter out low volume low thoisulphate/sliver bearing waters so they are acceptable to send them down the drain and be regulatory compliant.

I had one given to me and discarded it but the thing looked a bit like a toilet tank on a stand.

There was an electronic sensor that measured the ionic conductivity of the discharge water to tell you when you had loaded up the bead bed and were no longer sending out clean water.

There was a service company that renewed the bead cartridge to recover the silver, and you mailed them back and forth to keep a clean one ready to go.

I am not sure about printing paper, but I have gone to a modified Ilford rinse for film. I fill and dump three times, the modification is that I do a 5 minute soak, a 10 minute soak, and a 20 miniute soaks, based on the idea that the earlier soaks reach saturation quicker. Film now 3 years old shows no sign of fading or yellowing.

I would guess you could do about the same with RC paper, fiber would need many more soaks, 7 to 10 at a guess, but they could be shorter. I would try 1 minute, 2 minutes, 4 minutes... for a first test series. So if you rinse tank was, say, one gallon, you would need a maximum of 10 gallons of water. Hypo eliminator would allow you to reduce that.

The strange thing is that as I get older I find myself looking for cheaper easier ways of doing things instead of quicker ways.

djkloss said:

first of all, thank you all for your quick responses. alot of good information here. because we are using a spring for our water supply, I don't want to dump any chemicals in the ground. there is no 'gray water' tank here, it all goes to the same place in the septic system.........

Click to expand...

You would obviously dispose of processing solutions (developer and fixer) so that they would not contaminate your (or your neighbour's) groundwater. But you don't have to worry about a little thiosulphate from your wash water getting into the environment. It is used in many municipal water treatment plants.

You can get better archival results using two-bath fixing which enables silver-laden fixer to be washed out more effectively, especially if hypo clearing agent (wash aid) is used. Plain sodium sulphite is quite effective, rather than buy a commercial product (which is a little better but not by a huge amount). Using two-bath fixing would help lower to an absolute minimum any silver compounds in the wash water. Although it's a bit inconvenient having an extra tray, it is actually more economical in use of fixer.

Is the water supply from the spring in short supply? The instructions for my Summitek cascade washer say that very low flow rates are sufficient to wash fibre prints. They suggest 250mL (1 cup) per minute for the 11"x14" size washer.