Automated processor, which rinses can be mixed?

[dutchsteammachine]

I have got some experience hand developing B/W film and would like to build an automated developer machine that uses pumps and valves to move baths around and an actuator that turns the developer tank back and fourth.

I want to work on a minimum viable product first, so the least amount of required parts as a proof of concept.

So I am wondering which rinses I can combine into one rinse tank to save parts and also water.

For the steps I am thinking:

Rinse 1
Developer bath
Rinse 2
Fixer bath
Rinse 3
Final Rinse

Which rinses would be safe to combine and re-use in one source tank? And would this be different and more critical for colour processi?

Regards,
Niels

 

[BMbikerider]

Will you be doing a pre-rinse which is your first stage? This is strictly not necessary, especially for B&W. I have never ever used a pre rinse for B&W in over 60 years of home processing.

The rinse after the developing step that would be fresh water so that is not contaminating anything, but the final rinse after the fixing step really needs to be fresh water too, otherwise you risk getting drying marks from what it rinsed previously.
I don't know what water type you have in your part of the Netherlands but if it is what we call 'hard' water, that is to say if there are dissolved traces of limestone in the water then that will also increase the risk of drying marks.

If your system intends to include recycling the same water for several processes, that would not be a way to success. Especially with colour. Any contaminants before using colour developer can seriously run the risk of poor colour or even failure. That is a big no no. (Don't ask me how I know!)

If it is your idea this may save you the initial cost of the water and/or for environmental reasons, personally I don't think it is worth the risk.

 

[dutchsteammachine]

I do want to focus on making just a B/W capable setup first, so I don't need to buy and program a gazillion valves and pumps because colour has a lot more baths.

I was thinking of doing the pre-rinse but I guess it is not required right now.

I think water hardness here is managable here, I do the final Rinse with demineralized water but I get streaks regardless.

So the program would then be:

Developer (tank 1, tab water and developer)
Rinse (Tank 2, demineralized water)
Fixer (Tank 3, tab water and fixer)
Rinse (Tank 2)
Final Rinse (Tank 4, demineralized water)


Or do you recommend the first and second rinse to also have their own tanks?


Problems I am forseeing is how fast I can pump fluids around, does it need to be in the order of seconds or can it also take a minute?

 

[BMbikerider]

I do want to focus on making just a B/W capable setup first, so I don't need to buy and program a gazillion valves and pumps because colour has a lot more baths.

I was thinking of doing the pre-rinse but I guess it is not required right now.

I think water hardness here is managable here, I do the final Rinse with demineralized water but I get streaks regardless.

So the program would then be:

Developer (tank 1, tab water and developer)
Rinse (Tank 2, demineralized water)
Fixer (Tank 3, tab water and fixer)
Rinse (Tank 2)
Final Rinse (Tank 4, demineralized water)


Or do you recommend the first and second rinse to also have their own tanks?


Problems I am forseeing is how fast I can pump fluids around, does it need to be in the order of seconds or can it also take a minute?

I have just sent you a PM

 

[Craig]

Kind of sounds like you are wanting to recreate a Jobo processor. They pump the chemicals into the tank in about 10 seconds, and they allow a 15 sec drain at the end of each process. A stop bath is only 30 seconds, so the chemical needs to get into the tank fairly quickly. Similarly, if you have a 5 or 6 min developing time, it can't take a minute to get the developer into the tank - that's a big portion of the developing time. It would also depend on how the film is configured, if it take a min to get developer in, is part of the film in contact while the developer is filling? If so, then you are going to have some part of the film in contact with developer for a min longer than other parts, and you'll have uneven development.

The rinses are connected to the mains water, but after developer is a stop bath, which is treated as it's own chemical. That's fully programmable with a Jobo, so it could be a water rinse in place of stop.

The Jobo uses air to move the chemicals, it has a selector to direct air to the correct chemical storage bottle, which then pressurizes the chemical storage bottle slightly. There is another tube that then goes to the tank with the film in it, and the air pressure pushes the chemical out the delivery tube into the film tank. I don't know how it meters the amount of chemical it pushes through, but it does somehow.

 

[dutchsteammachine]

Kind of sounds like you are wanting to recreate a Jobo processor. They pump the chemicals into the tank in about 10 seconds, and they allow a 15 sec drain at the end of each process. A stop bath is only 30 seconds, so the chemical needs to get into the tank fairly quickly. Similarly, if you have a 5 or 6 min developing time, it can't take a minute to get the developer into the tank - that's a big portion of the developing time. It would also depend on how the film is configured, if it take a min to get developer in, is part of the film in contact while the developer is filling? If so, then you are going to have some part of the film in contact with developer for a min longer than other parts, and you'll have uneven development.

The rinses are connected to the mains water, but after developer is a stop bath, which is treated as it's own chemical. That's fully programmable with a Jobo, so it could be a water rinse in place of stop.

The Jobo uses air to move the chemicals, it has a selector to direct air to the correct chemical storage bottle, which then pressurizes the chemical storage bottle slightly. There is another tube that then goes to the tank with the film in it, and the air pressure pushes the chemical out the delivery tube into the film tank. I don't know how it meters the amount of chemical it pushes through, but it does somehow.

Thanks Craig, I wanted to ask for timings. I will try to keep things to 10-15 seconds. Will need to think about fluid dynamics a bit I guess, ouch.

How does the jobo take care of contamination between chemical baths? Does the rinsing clear out the previous residual chemicals well enough?

Very interesting that is used pressurized air. I guess the benefit is that no pump touches the chemicals? My thought was to have a single pump, but one of those types that uses a hose not a centrifugal.

Does the jobo heat up all the tanks to the same temps? Does it over heat a little bit?

 

[halfaman]

I can tell that Jobo CPP and CPE machines have all a carryover between baths when used with lift.

Why not use acid stop between developer and fixer? It has a good capacity and it can be replenished.

 

[Steven Lee]

Problems I am forseeing is how fast I can pump fluids around, does it need to be in the order of seconds or can it also take a minute?

This depends on how much liquid you're pumping. Yes, all machines are slow at pouring chemicals but they utilize rotary agitation which doesn't require much chemistry. Moreover, they're pumping while the tank is rotating which helps speeding up the chemical distribution inside.

You probably have done your research, but in case you haven't seen some and looking for inspiration, the similar machines I'm talking about are: automatic JOBOs, Filmomat, Dev.a, Phototherm, and Midtone Machines.

 

[Craig]

I have the Autolab 3000 machine and it has a large waterbath that is temperature controlled to keep the chemicals at the desired temperature. There is a hose from each chemical bottle to a funnel in essence that delivers the chemicals to the tank, so there is no contamination between chemicals.

I can program the rinse/wash times as long or short as I want, including zero. I don't have a rinse between stop and fix for example.

I think the chemical delivery is under 10 seconds, but I've not timed it. I'm usually working with about 300ml of solution for the sizes of tank I'm working with. It has hardcoded 15s drain time built into each cycle. So for example if the bath time is 3 min, it will rotate for 2:45, then lift the tank to drain for 15s, and pump the next chemical in at 3:00.

Mine has 12 chemical bottle, so it could do a 12 chemical process, or it's also set up to have C41 in 6 bottles and E6 in the other 6, so I could switch back and forth easily. It has an air supply and delivery hose from each bottle, so only needs a single pump. By using air, it doesn't have concern about the pump corroding from the chemicals, the chemicals are just going through plastic tubing.