Darkroom sink materials

[polyglot]

I'm considering making a custom fibreglass darkroom sink - actual sinky bit at the left and a big long ribbed bench/swill wet area that I can place trays or a Jobo on and just tip them over when I'm done.

Does anyone have any information on whether any of the standard resins are susceptible to any photo chemicals? Epoxy is nearly everything-proof but it sucks to work with so I'd like to use the polyester resin if possible. I know you can get special "chemical resistant" polyester resins too - does anyone know if there is a common type in particular that I should use for a darkroom sink?

I found this table that seems to show polyester as resistant to most stuff at 15C but resistant to not much more than water (no thiosulphate!) at 65C. What worries me is what will happen when I dump 37C bleach or fix from a colour process and maybe spill a few drops or even forget to put a container under the dump pipe. And of course there will be dilute chems coming out after each wash.

 

[BetterSense]

Polyester resin sucks. Use epoxy resin. If you search you will get a lot of threads about homemade sinks. I made mine out of plywood and Moorlastic. Also fiberglasssite.com has inexpensive materials.

 

[Neanderman]

I used the standard fiberglass fabric and resin that you get at the auto parts store to line a 3/4" plywood shell, which I heavily urethaned on the outside. Eleven years later and it still looks almost like new.

Ed

 

[snapshot2000]

About 20 years ago, I did mine the same way as Ed described, following directions in "The Darkroom Handbook" (Dennis Curtin & Joe DeMaio). I don't remember if I got the fiberglass resin & cloth directions there, but the book had a good frame layout that I used. I also painted the inside of the sink white using marine paint. I had it for several years before I moved and had to sell it. It was bought by the guy who ran the local camera shop. It still looked great when I sold it.

One really bad thing about the resin though: the brush was dragging and pulling the cloth out of place as I was brushing it on, so I put on a pair of plastic gloves and started working with my hands. I thought it felt really warm and was dismayed to lift my hands and find that the gloves had simply dissolved. I had fiberglass hands for well over a full week, maybe two. Also, the sink sides had a few blister areas from where the cloth had sagged and hardened, but these were merely cosmetic.

Dan

 

[polyglot]

Did you guys make a concave structure that remained with the sink, or a proper plug mould? In other words, did you:
- build a sink out of wood and line it with fibreglass, leaving the inside/working surface as raw GRP then install the whole thing, or
- build an anti-sink out of wood, line it with fibreglass, pop the wooden plug out and then just install the fibreglass shell?

I've seen the former done a couple of times where the mould is the frame, and it works well but is kind of ugly. The latter appeals to me because if I make the plug smooth enough, I can get a nice smooth finish on my sink and I can give the mould away for someone else to use - I know a guy who does fibreglass for his living that will supply me the raw materials and he could maybe use it if it was any good. The latter case is a little more difficult though because you have to mould enough structure into the fibreglass for it to be self-supporting and carry a large uneven load without cracking; in the former case, the wooden mould is always there as support.

Dan: what is this "marine paint" of which you speak? There are of course many, so if you know anything about the particular one you used that'd be very helpful to me.

thanks!

 

[snapshot2000]

Wow, that was so long ago. I only remember that it was white paint with some slight texture. It was made to paint boat decks to keep you from slipping, I think. It was probably oil based, but I'm not sure. (That was in the early 80's).

RE: the frame - I built the basic sink frame from plywood, then places support pieces (1x1's, I think) along the bottom in a way that would create a slight slop when the plywood sink bottom was laid down on them. Once that was all put together, I drilled out a drain hole, then did the fiberglass cloth and resin thing.

I think that book I mentioned is still available, and there's probably an updated edition. I used the marine paint both to add some waterproofing (just in case) and to make it a nice white. I kept it clean and it never stained on me.

 

[snapshot2000]

Also, the sink frame had spacers for drying screens on one side and slats for bottle and tray storage on the other side.

 

[Trond]

I built my sink based on ideas in "Build your own home darkroom" by Lista Duren & Will McDonald. It's made of plywood and painted with four coats of epoxy paint. The paint is very strong, and is usually used on garage floors, etc. I personally wouldn't bother with fibreglass.

Trond

 

[polyglot]

Actually I like the idea of the epoxy paint. I've used it (well, the clear version intended for floorboards) before on a work bench and it's pretty hard-wearing. I still like the idea of doing a fibreglass sink, but I could make it from polyester resin and paint it with epoxy for the chemical resistance.

thanks!

 

[jeffreyg]

My sink of thirty-five years: 3/4 inch marine plywood, fiberglass cloth covering the bottom and a couple of inches up the sides and all including the tops* coated with marine polyester with almost 18% gray coloring added.

* loose 3/4 inch plywood pieces that can cover the the sink to make additional work surface when the sink is not in use.

http://www.jeffreyglasser.com/

 

[Neanderman]

Did you guys make a concave structure that remained with the sink <snip> did you build a sink out of wood and line it with fibreglass, leaving the inside/working surface as raw GRP then install the whole thing

This was my approach (though I'm not sure what you mean by "raw GRP"...

Did you build an anti-sink out of wood, line it with fibreglass, pop the wooden plug out and then just install the fibreglass shell?

This could be one approach, especially if you were at all interested in making more than one (or if, as you indicate, you know someone who does this kind or work.) But for a one off, I think in the end it's a lot more work.

Mine is really quite basic -- all of the internal corners are square. I drilled the hole for the drain before I glassed it to minimize swelling of the wood due to any leaks around the drain, (which is a non-type 316 stainless steel insert purchased at a home center, so it developed some rust spots pretty quickly) and I think I only used one layer of fiberglass cloth. At the most, I used two. I did put down multiple coats of resin, so I'd have as smooth a surface as possible. The resin was spread using a rigid plastic 'squeegee' of sorts that you can get at the auto parts store.

Once the resin has hardened and is thick enough for your tastes, having a sander to smooth it out is helpful. I wish I'd had my random-orbit sander back then as I think I could have made it even nicer.

I occasionally think about reworking it with some more fiberglass, but it's a big job and the sink is functional as it is, so I live with the little defects. Fiberglassing is an art and I am no master.

 

[BetterSense]

I also bought a 'bar sink' drain at Lowes. It immediately rusted.