DIY Vertical Slot Processor

Hey, everyone! Long time listener, first time caller.

I've been printing in a basement storage room for the last couple of years. I print in trays so far, but have been intrigued by the idea of vertical slot processing. I've seen the Nova processors, and a few examples of DIY processors, but had expected I'd see more. I recently came across the Optima Darkroom line of processors and find them quite intriguing. After trying my hardest yet failing to find a way to justify the price, I decided that it could be a fun project to try to make one!

I've worked with acrylic in the past in service of my aquarium hobby, so I bought some acrylic and epoxy and got to work. The build is pretty straightforward.

My first prototype didn't work out, as the slot was too narrow and the photo paper would simply stick to the front face. I switched to a textured HDPE backing layer and made the side rails 1cm wide, and this second prototype seems to work quite well. I just finished my first printing session with my second prototype and I'm pretty excited with the results so far!

I initially just stuck the paper directly in, allowing it to stick to the back layer, but it was super challenging to get out with my rubber tipped bamboo tongs. I then folded over a corner of some old photo paper that I used for dodging and use that as a carrier. The folded bottom sticks out enough that nothing touches the front surface of the photo paper.

Here are some photos of my set up at this point. This is just water with a black and white experimental print, as it's not a terribly interesting photo without anything in the slot. I've got a temporary stand that I threw together tonight so I could try it out, but I plan to cut a nicer looking stand from acrylic and make some more slots for my bleach and fix. Finally, I'm thinking that I'll get a small aquarium that I can put this whole setup in with a fish heater or two to keep my chemistry at temp.



I'd love to hear any thoughts or feedback. This has been a fun project, and it's nice to see it working given my...adequate skills.

This is just a single slot, right? Are you planning to make more slots that will be separate duplicates of this one, or will they be glued together?

I made a homemade 3-slot tank for dev/stop/fix for 8x10" (I hesitate to call it a processor) in the mid-90s as a student with little space. I will attempt to describe it. It was basically 4 sheets of clear acrylic each about 12x12", not sure how thick maybe 1/4". The spacers between the slots were square acrylic rod (maybe 1/2" or 3/4" square) cut to length to make the sides and bottom of each slot (so roughly 34" of square rod per slot). The acrylic came from a plastics store on Canal St. NYC that sold all kinds of useful things. I glued it together with an acrylic solvent, I think methylene chloride - this is really not good stuff and not advisable today, even then I knew enough to only use it outside. It leaked a little, slowly, so I stood it in a tray when filled.

I think I just used thin bamboo tongs (no tips) to put the paper in out, and to move it a little for agitation. This worked (btw I was using just RC paper); you can touch the front of the paper with the bamboo tongs without problems, with a light touch. I don't recall if I had lids for the slots, I may have just put plastic wrap over it.

It did have two issues: it was fairly heavy, especially with liquid in it; and since it had no drain valves/plumbing, draining the 3 slots is a nuisance, if you want to get the liquids into separate bottles (which allows reusing the stop and fix, proper disposal of fixer, etc). Ultimately, it might have been more practical to build a rack that held 3 8x10 trays one atop another.

The tank-beast actually still exists but is in my parents' attic and usability is unknown. Someday ...

Thanks for sharing!

reddesert said:

This is just a single slot, right? Are you planning to make more slots that will be separate duplicates of this one, or will they be glued together?

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That's correct. So far this is a single slot. My plan is to make two more that can join this one in a little rack. They won't be glued together, they'll just sit in the rack, so that they are individually movable and so that there'll be a little space between them for water. I'm thinking I'll put them in a small aquarium with water and a heater for temp control, as I print RA-4 and haven't yet been able to do it at the recommended temperatures.

Nice!

If you are printing 8x10 size consider using a Kodak 4a stainless steel film hanger. I've used these in my Jobo Duolab slot processor. Jobo used a wand with tiny suction cups to manage (RC only) paper

These are overpriced IMHO

You can find used 1 gallon vertical SS tanks that are small, easy to manage, 3 tanks side by side probably only 10 inches of counter space.

Here is a material you might try. It is PVC board and is very easy to cut and work. It is sold in different thicknesses and surfaces. I have used it in the past for projects. I am not affiliated with them. https://www.kommerlingusa.com/products/komacel/

One of the nice things about plastic vertical slot tanks is that with narrow slots you could make them to be very economical on chemistry, like roughly 1 liter / quart of chemistry per slot for 8x10".

I never thought of using steel hangers for the paper, although that seems in retrospect obvious.

Thanks, I haven't done large format yet, so haven't come across film hangers before. That might do well!

reddesert said:

One of the nice things about plastic vertical slot tanks is that with narrow slots you could make them to be very economical on chemistry, like roughly 1 liter / quart of chemistry per slot for 8x10".

Click to expand...

That's exactly what this slot takes! In the photo it is filled with 1 liter.

Additionally, the technical theory section of the OptimaDarkroom site claims that oxygen only penetrates 15mm beneath the liquid's surface, and that oxidized chemistry is less dense than fresh chemistry. That suggests that with a small surface area a smaller portion of the chemistry will oxidize, and when it does it will rise to the top, creating a buffer to protect the rest of the chemistry from oxidization. In theory that should allow the chemistry to last longer against oxidization.

My folded paper to hold the print was inspired by the OptimaDarkroom print holder. With the RC paper facing out, this allows the paper to cling to the older instead of the container, while nothing touches the surface of the paper and the tabs ensure it doesn't rest against the front of the container. In my test prints last night using a very hacked together version of this worked quite well and resulted in good (for my skill level) prints!

rharter said:

Thanks, I haven't done large format yet, so haven't come across film hangers before. That might do well!


That's exactly what this slot takes! In the photo it is filled with 1 liter.

Additionally, the technical theory section of the OptimaDarkroom site claims that oxygen only penetrates 15mm beneath the liquid's surface, and that oxidized chemistry is less dense than fresh chemistry. That suggests that with a small surface area a smaller portion of the chemistry will oxidize, and when it does it will rise to the top, creating a buffer to protect the rest of the chemistry from oxidization. In theory that should allow the chemistry to last longer against oxidization.

My folded paper to hold the print was inspired by the OptimaDarkroom print holder. With the RC paper facing out, this allows the paper to cling to the older instead of the container, while nothing touches the surface of the paper and the tabs ensure it doesn't rest against the front of the container. In my test prints last night using a very hacked together version of this worked quite well and resulted in good (for my skill level) prints!

View attachment 395480

Click to expand...

Keep us posted!!