Print washer

[dario]

Hi folks - I'm embarking on making a print washer - can't afford to buy one and ship it to the end of the world.

I have in mind a something like the Summitek, which has a very low water flow requirement.

Could anyone with one please describe how the water gets from one print compartment to the next?

Do the low partitions have small holes near the top edges or perhaps nicks or short vertical slots through which the water flows (leaving the top edges of the partitions a little above the water level)? Or do they have perfectly smooth edges (in which case the partitions are completely submerged).

It seems to me that if they have just smooth edges, the washer would have to be levelled very precisely to get an even flow of water over the partitions at all points along the length of the washer. (I know the washer it sits on only three feet to facilitate levelling.)

On the other hand, having short slots (maybe half an inch deep) would allow for a the washer being a little off level and still get water through all slots.

Thanks

 

[RalphLambrecht]

... Could anyone with one please describe how the water gets from one print compartment to the next? ...

Hopefully not at all. The optimum print washer has separate print compartments. Each compartment should have its own in and out, otherwise, adding a print will contaminate prints already in the washer.

 

[dario]

Hi Ralph - Well, true, but the Summitek washer (and others of that ilk) has a cascade of compartments, so adding a print doesn't contaminate those already in the washer. And, if there are N compartments, it uses 1/N of the water.

 

[RalphLambrecht]

Brilliant, but why are you asking the question then?

Summitek's website reveals how the water flows from one compartment to the next:

http://www.summitek.com/cascade.html

 

[tkamiya]

I have a washer that I bought second hand. I have no idea of make/brand/model. It is a one piece plastic shell that had been molded and inner assembly that separates prints. This separator is just sheets of plastic separated by spacers in very long bolts. It's slightly smaller than inner part of the shell. It isn't sealed or anything. It has about 1/2" gap at both ends. About enough space to have the tubes I am about to describe at both ends.

The "shell" has two tubes. The inlet tube enters the tub from the side but near the top. It has holes at its length and each one corresponds to spaces between the spacers. The outlet tube is floppy and it sinks to the bottom but it also has a small hole at the maximum water level. It exits from side near the top as well. Those tubes are opposit end end of the shell.

I believe the intent is for water to flow from top of one side to the bottom of the other, sort of diagonally. Because of partitions, there aren't all that much mixing between compartments except for slow diffusion. Amount of water that can pass through is limited by the exahust capacity. If too fast, it overflows.... It can handle very slow flow at near trickle.

 

[RalphLambrecht]

The process of print washing is a combination of displacement and diffusion. In other words, you want to rinse the prints off first, to get excess fixer removed quickly, after which you want the print in the washer to slowly diffuse the remaining fixer out of the emulsion and the paper fibers. Only slow flow rates are required to do so.

 

[PeterB]

How does the paper not stick to the partitions?

Wow, this is the first time I have seen the Summitek and I'm impressed by its design. it's a shame the mfg. has gone out of business. if anyone owns one can they tell me how the prints are kept away from the partition walls (which must be solid).

I'm actually in the process of modifying the design of my (there was a url link here which no longer exists) to optimise its washing ability and might even consider a more extensive design change towards that of the Summitek if time permits.

 

[2F/2F]

Is this "cascade" design a zigzag flow like the Eco-Washes? (Water goes down one compartment, around the bottom to the next compartment, up the second compartment, and over the top to the third, flows down the third, etc.) If so, as long as you add a print "downstream" of the ones that are already in the washer, you are probably not measurably contaminating those already washing.

I prefer to rinse prints well, then have them sit in a holding tray until I start a timed flowing-water wash on them all at once, to avoid worries about contamination in the washer and unequal times in the flowing-water wash.

At any rate, I don't have any experience with a Summitek washer, but I can explain roughly how an Eco-Wash is designed. Yes, your idea is correct. The partitions which the water flows over are notched. I assume the ones that the water flows under are not notched, but I don't think it would hurt anything if you did notch them (and it would make all of the partitions interchangeable and simplify the making of the washer by requiring fewer unique parts to be designed and made). Flow starts at the top of the first compartment, though you could probably also start at the bottom just as well. Obviously, every partition that has water flowing over it is at a slightly lower height than those that have water flowing under them. You could make all of the partitions identical/interchangeable by using two different lengths for the slots that are cut for the partitions, to set their alternating heights; the alternative is to have partitions of different heights and slots of the same length. In the latter case, only every other partition is interchangeable, and you must make two different types of partitions (one shorter and notched, and the other taller and not notched).

 

[dario]

Thanks 2F/2F. You've picked up the point of my question. I should have noted that the Summitek is a cascade washer. And you make a good point about making the partitions interchangeable. That would be of some convenience.

Could you describe the notches please? Depth, width?

Also, what is the difference in height between the higher and lower partitions? Half an inch, maybe? Or less?

PeterB asks about the prints sticking to the partitions. I've thought about this and haven't yet fixed on a solution, although I've been told that it's not a problem. If nothing else, apparently, the fixer can all diffuse out through one side of the paper, although I wouldn't like to rely on that. One possibility is to use partitions that have a textured surface. Another idea is to drill a row of wee holes near the tops and bottoms of each partition then thread a thick nylon filament through the holes so that each side of the partition is covered with a series of vertical strings. Sounds a bit untidy, but if it works, who cares?

 

[dario]

Thanks also tkamiya. Your description is good. It's clearly not a cascade washer, but it has given me another idea about how a cascade washer might be constructed.

 

[RalphLambrecht]

... One possibility is to use partitions that have a textured surface. ...

This was done for my washer and it works very well.

 

[tkamiya]

On mine, there is no special device preventing from prints sticking. However, the plastic dividers are made out of textured plastic material and not super smooth like Plexiglas. With water flowing and flowing around the prints, they float nicely between the dividers.

 

[2F/2F]

Could you describe the notches please? Depth, width?

Also, what is the difference in height between the higher and lower partitions? Half an inch, maybe? Or less?

The notches are spaced perhaps 1/2 inch apart from each other, and they are not even 1/8 inch deep or wide.

The difference in height between every other partition is somewhere from 1/2 inch to 1 inch. (I am doing this description without the washer in front of me, as it is not mine.)

Maybe frosted Plexiglas would help prevent sticking.

Each compartment is about 1/2 inch wide.

You need a rubber-tipped fishing pole as well, to pull the prints out.

 

[Martin Aislabie]

The process of print washing is a combination of displacement and diffusion. In other words, you want to rinse the prints off first, to get excess fixer removed quickly, after which you want the print in the washer to slowly diffuse the remaining fixer out of the emulsion and the paper fibers. Only slow flow rates are required to do so.

Ralph makes a very important point- if you are concerned about water consumption

If you rinse the fix off a print, then the amount of water you need to adequately wash it is surprisingly low.

I am not sure, but I think I saw an article from Ilford many years ago that showed a 10x8 could be washed to archival standards with less than 1 litre of water.

Martin

 

[ROL]

Perhaps I can add a pragmatic perspective to the otherwise fairly accurate, albeit theoretical tenor of this thread. I routinely use four different designs of print washers (see this, if you need a picture).

1. Flat Style
   I use a simple flat washer for holding and pre-wash of up to 16X20 ("mural washer" for greater than 16X20).
   
2. Cascade Style
   A 16X20 Cachet Eco Wash of the same apparent (common) cascade design of the Summitek is used for prints up to 16X20. It has a reservoir inlet and outlet (on the opposing side) at the top. 12 slots are created by 11 identically sized, smooth acrylic (plexi) panels, alternating in height. Every other one (high dividers) is raised enough to allow water to pass underneath, while alternates (low dividers) allow flow over their tops through notches, just as in the Summitek diagrams. I don't believe notching is absolutely necessary with this design, but leveling is. Prints just don't stick to the panels once inserted. They can be difficult to insert if not entirely wetted. This is another good reason to use a pre-wash/holding bath. The idea of this washer design is that it functions essentially as an automated, slow–diffusion, fill-and-dump. If memory serves, I believe Steve Anchell made a study of these washers and determined that they were the most efficient, because of the ease of diffusion and water consumption, at cleaning prints of hypo. If concerned about the outflow "contamination" of downflow prints, just observe the first in, first out – inflow to outflow – protocol of the the slot locations.
   
3. Cross–Jet Style
   For prints up to 20X24, I use a Calumet (Gravity Works?) cross–jet style washer, which essentially provides each print with its own independent inlet and outlet. The same care must be taken to insert less than saturated prints as with the cascade style.
   
4. Mural prints up to 30X40 are washed in a flat washer of my own design, which functions primarily as a fill-and-dump style washer.

I have never experienced any washing problems with either style of washer and would rate them the same, except that the cascade style uses much less water. If I had a choice (rather than using what I have for the required print size), my preference would be that all my washers, including those for murals, be cascade style. But, admittedly, my prints may be washed fairly well before they ever enter the washers, as they are pre-washed in holding and receive a brief hypo-clearing wash prior to full washing.

 

[RalphLambrecht]

... If I had a choice ..., my preference would be that all my washers, including those for murals, be cascade style. But, admittedly, my prints may be washed fairly well before they ever enter the washers, as they are pre-washed in holding and receive a brief hypo-clearing wash prior to full washing.

This is an often overlooked point when discussing print washing. Most washing sequences are a mixture of rinse (displacement), HCA (chemical support) and washing over time (diffusion). Due to my workflow, by the time my prints enter the washer, most of the fixer is already gone.

By the way, great darkroom design ROL! Looks very neat and comfortable. Something, I believe, that is important for quality work.

 

[dario]

Thanks everyone for your input. I think I've got it sussed now.