The Darkroom Sink Build

My plan is to build a proper darkroom sink for all my needs from traditional darkroom prints, Lith process and other alternative processes. The sink should be waterproof, chemical resistant and should last at least 20-30 years of service.

Even though I had already started searching about to see if I could buy a used one. They do appear once or twice a year on the second hand market. Unfortunately I couldn’t find anything suitable. So hence I decided to have a go and build my own!

This build will explain the parts, links as well, and include instructions along the way for each stage of the darkroom sink construction.

Background Story

The concept of building a serious darkroom sink might seem mad in this digital day and age. This year I built my darkroom partially for Ikea kitchen units and some kitchen worktop I got at local hardware store. My worktop area is about 3 metres long and 90 cm wide. This served me well for 8×10″ or 18x24cm prints and the occasional large prints. I had all my trays on the workspace, developer, wash, fixer and sometimes toner. But now I wish to make 24x24" or larger prints!

After each darkroom session I needed to clean the worktop down and the tray too. It’s a laborious task of scrubbing for 20-30 minutes. I had also made a divider to separate the wet and dry areas of the workspace. As chemicals tends to splash and go everywhere which you don’t want on your enlarger baseboard or negatives folder. The wet and dry areas in a darkroom needs to be separated well.

At the time I had also ventured into the world of Lith process. Wishing to make much large pieces of artwork. That’s where the sink comes essential. The process requires a large tray and agitating for the duration of 5- 45 minutes depending on the chemicals and papers. That’s where my problems began. Chemical would splash and chemical spots would get onto anything next to the tray. Consider the process is under low visibility – red light usually.

If you can imagine 4 to 6 substantially large trays for a entire workflow. That’s a lot of splashing about! It then becomes resoundingly clear that a long and wide sink is essential.

Supplies

Sink Panel - Part List

Plughole - Part List and Tools

Sealing with Epoxy - Part List and Tools

The Design

Film Photography - Building a Darkroom Sink

My design was simple, as I wanted it cut to size locally or online whichever made sense and was within budget. While they are a couple of way to tackle this task from plywood, OSB wood plate, fibre glass and even carbon fibre too. I initially hadn’t decided. I made my design in Tinker CAD as shown below. I finally decided to make mine a bit longer than originally planned as the length of the wooden plate were 2500mm longer. I settled for 2500mm x 800mm with 21mm thickness.

I watched many videos to get inspiration and technical knowledge. It seemed clear that epoxy resin will need to be involved. Many DIY-ers and course boat builders swear by epoxy, for example from West System. The epoxy and filler is needed to seal the joints and the surface of the sink.

Instructions

The plywood panels I managed to get hold off from a local DIY store, are phenolic resin coated, BFU 100 – weather resistant. Because the panels are already strong, thick and well sealed, 2-3 layers of epoxy resin is really only needed. Phenolic resin is also chemically resistant.

(The German description for these panels are Siebdrucksperrholz Pappel Sieb/Film 1250x2500x21 mm.)

Using two of the lengths for the front and back panels. Spread a line of contact glue on the length.
Align the lengths centred to the panels, one end flush to the edge while the other end raised by 1cm. This is for the water to flow into the sink plughole.
Cut the last length to size for the size panels, screw and glue the length on. One length should be flush to the edge while the other raise by 1 cm.

Making the Sink Plughole

This will required cutting a hole into the bottom panel not a task for the faint hearted. I used a router to make a 3mm inset around the plughole so it sits flush (Best to watch the video on this page, to see it exactly). When choosing a plughole assembly, pick something straightforward. Keep in mind the sinks wood panel is 21mm thick.

*Use a test piece of wood to calibrate you insets for the plughole before attempting to work on the sinks bottom panel.

Cut the hole for the plug hole and ensure it fits using a drill saw hole bit.
Use a template and set the router to remove 2-3mm so the plughole is sunken into the sink.
Round the edge with 10 or 12 mm rounded router bit.

Sealing the Sink With Epoxy

Film Photography - Darkroom SInk (Part II)

It’s important to wear gloves as epoxy resin shouldn’t make contact with your skin. I recommend using some thick washing up gloves, I did try the normal nitrile gloves which I use for the darkroom work but they ripped so often, I switched over to the thicker washing up ones.

Also you’ll need a new brush for each session!

I did use calcium carbonate initially, as already have some in my darkroom for cleaning glass plates for wet plate collodion. However I ended up using the West System 406 over the my initial attempt. The West System 406 is so much better and fit for purpose over calcium carbonate as a filler.

Instructions

Layer down the glass fibre webbing and apply the first coat of epoxy with a plastic spreader or paint brush.
After 24 hours of curing, sand down the entire sink. This will help the bonding when the second epoxy coat is applied.
Seal the corners with an epoxy resin filler mix. I’m using West System 406 mixed into my epoxy to make a peanut butter consistency.
Apply the second coat of epoxy.

Sealing the Seams of the Sink

The seams and joints need attention to ensure that they are well sealed against water leaks. You’ll need to use an epoxy filler for this like West System 406. To hide my initial messy filling and sealing of the sink, I coloured the epoxy with “Silver Black” pigment powder into the epoxy - this is optional

First measure out part A + B of the epoxy and mix it well.
Then add a scoop of pigment powder to get the colour you wish. Again mix well.
Finally add in the filler powder and mix well. The consistency should be like peanut butter so it sticks and holds well in the seams and corners.

Conclusion

Now that the sink is finally plumbed into drain which seemed harder than it actually was, after some wrangling and overthinking the problem out too much, a visited to the local DIY hardware outlet resolved most, if not all of my concerns. Currently I'm still using a hose pipe connected to my existing sink for water right now but once I have time I'll tackled that issue another time. For now at least, I've again have a working darkroom and ready to produce artwork once again, I'm excited!

A mammoth undertaking for a mammoth size sink. What I can say I already feel the relief of having more space to work with without the worry of water going into place where it shouldn't.

I feel some alternative photography work is on the cards, such as Cyanotype or even VanDyke Brown or maybe some traditional prints at least that's the plan.