Query for good darkroom sink materials

I posted this question as a response to an older thread, then

realized no one was going to find it.

 

I'm about to build my third darkroom sink. I'm using exterior grade

plywood and pressure treated pine. The question is what to coat it

with. My first sink was covered with an epoxy paint. It worked out

pretty well, needing an occasional touchup on account of the

developer stains. For my second effort, I used polyester resin, but

with out the glass cloth. That was pretty okay, too.

 

For my third sink I would prefer to paint rather than use the

polyester resin. But I'd like to hear from anyone who has tried

recently available, and perhaps improved, paint products. In

particular, I'm debating epoxy paint vs. polyurethane paint.

 

Another question has to do with the best wood glue to use. here'

I'm debating between elmer's polyurethane glue, which claims to

be "waterproof" vs. Tite-bond II, which claims to be highly water

resistant. My hardware store recommended the latter; but waterproof

sounds better to me than water resistant.

 

Thanks in advance for any and all advice!

My experience with wood sinks both painted and resin/fiberglass cloth/mats has

been largely successful. I've used epoxy and polyurethane paints on the inside and

outside of sinks. My experience is, that with properly prepared surfaces both work

well. However, they both stain easily. (as your experience has shown.)

 

Why are you going away from resin. Although fiberglass is a pain in the butt, it is

worth the effort. This is especially important in the corners. One sink I built for a

college darkroom is going great after 10 hard years and the inside of the sink looks

the same as new (The exterior was painted with epoxy so it is stained pretty badly)

 

As for the polyurethane glue vs. Tite-bond II, I used Tite-bond for that sink, but for

my own personal sink, I used the polyurethane. Polyurethane is a little sloppy because

it expands, but where I used it it doesn't show. The biggest problem might be that it

doesn't have much of a history. Who knows if it will just fall apart in 10 years. But,

based on polyurethane finishes, I decided to take a chance. Besides the fiberglass

resin will help hold it together.

 

Finally, I don't EVER use pressure treated wood. Cutting the wood can be pretty toxic

(especially the cyanide formulas) My sink has polyurethane paint on the legs and

exterior. This protects them from all but complete innundation.

Arrgh! Arsenic, not cyanide!!! (I must have been sucking on the arsenic)

How about That Rhino Liner stuff they spray in pickup beds?

Rob --

 

I've had good luck with PPG's 'Coal Cat' Coal Tar Epoxy. It's *tough* and quite inexpensive. I built a sink out of plywood about two years ago, and it's still going strong on the original paint job.

 

Like Model-T cars, it comes in any color, as long as it's black. It's also very thick; imagine a mixture of coal tar and epoxy and you won't be far off the mark. If it stains, I can't see it.

 

This is an industrial product, so you will probably have to order it from a PPG dealer, but I managed to find one in my area that carries it in stock. Coal tar epoxies are carried by other companies; do a Google search for 'coal tar epoxy' and you will find quite a bit.

 

I believe that this paint is used in places where you want to paint something *once* and not have to do it again.

 

Good ventilation is recommended when using this kind of paint; I painted my sink in the garage.

 

Here's a blurb from Benjamin Moore's coal tar epoxy:

This two component polyamide cured coal tar epoxy is a 4 to 1 mixture with good pot life. Offers very good splash and spill resistance to most acids, alkalis, and mild solvents. Forms good non-conductive insulating film for dissimilar metals. Provides very good adhesion, flexibility, and high film build on steel or concrete interior or exterior areas. Steel surfaces for immersion service should have near white metal blasting.

 

Recommended Uses

Interior or exterior concrete, metal surfaces, ballast tanks, clarifiers, digesters, cooling towers, offshore rigs, marine piping, spillways, bar screens and retainer gates, waste treatment plants, power plants, pulp and paper mills, fertilizer plants, foundries and refineries

 

Not for potable water service, not for immersion in strong acids and strong solvents, blushing occurs during high humidity and low temperature, limited low temperature cure.

 

Colors: Black

My fiberglass and epoxy sink is still going strong after 16 years. My only problem is that the plywood has bowed some. I have a high spot running down the middle of the sink. Helps tray agitation, hurts drainage. 8)

 

My suggestion would be to use Durham's rock hard water putty to smooth out transition from the bottom to the sides. Should be able to coat over that with no problems.

The BEST product bar none is West System Epoxy. Get the basic instruction book on boat building and maintence which will answer all your design and construction questions. This is a structural adhesive used in boat and airplane contruction and in combination with different additives can be used in a wide variety of applications.Get the booklet and you'll figure it out. Min 5/8 inch good one side plywood, screwed and glued (epoxy),two coats of epoxy(no matt), scuff sand and then finish simply with a polyurethane floor enamel which is easy to recoat if the staining gets to bad. West system is a time honoured marine product that will outlast most of us. -N.

The reason I thought I might avoid resin is that I have the impression that it should only be used with glass cloth, to prevent it from cracking. I could be wrong about that. I did build a sink with resin-coated plywood, and it held up fairly well. But some people seem to feel the need for the cloth, sometimes even using two layers. I'm just trying to do everything right, so I won't have to start over.

 

Have others had good luck using polyester resin without the glass cloth?

one thing you could investigate is the PVC product--Sintra. Sold in 4x8 sized sheets up to almost an inch thick I believe in a variety of colors too...it can be heat formed, so unfortunately above 120-140 something like that (can't recall exactly), it's pliable. But you can pretty much treat it like a sheet of plywood and use table saws, rotary/orbital saws, drills, routers--you name it. you can use screws, glues, paints whatever with it--and it's pretty much water-proof and fairly chem resistant as well. they use in the exhibits shop near where I work for silkscreening signage & mounting photographs and some casework, but I've used a 2x3 sized scrap of it as a duckboard more or less for a sink in the darkroom for about 5 yrs now & it's held up fine. It's expensive though--about 80-100 bucks a sheet. I don't know if it would be 100% perfect for your application, but if you have a plastics supplier nearby, you might want to check it out. hope this helps.

Here's a completely different suggestion, but it's held up more than ten years for me. I glued formica to plywood, in the usual way with contact cement, and screwed the sink together with marine calk in the joints. It's really just a box with slight pitch and a drain. But it wipes clean, and shows no signs of wearing out.

I made a sink lined with PVC sheet. As the previous writer suggested it can be cut with a table saw to size. It takes PVC cement to glue seams. I have a detailed description of how to do this on Tuan's Large Format Page. I have made sinks before with epoxy, fiberglass, and urethane. ButAll had problems from outgassing to expense.

 

Regards, Mike

If you have a local fab shop, stainless steel is the "gold standard" for a darkroom sink -- 18

gauge 304ss or 305ss is plenty good, and easy to weld with an arc welder at 30 to 50 amps. If

you're thinner than 18 gauge, then a simple 120 volt MIG welder is easier to use so you don't

blow holes in the metal.

 

Alternately, look at restaurant supply houses for used stainless counters & sinks

"Anything worth doing is worth doing right!"

 

My sink is fiberglass cloth and polyester resin coated over 1/2 inch exterior grade fir plywood. I constructed it in 1968, supported myself and my family the whole time working as a photographer, and still use the sink. The little extra expense/time/effort of using glass cloth with the resin will pay off in greatly reduced maintanance over the the years. Do it right.

One fellow above recommended Sintra - if it's the same stuff I've seen locally here, it scratches very easily, and would become quite dinged up after a short period of time. But, he might be talking about something else.

 

I built my two sinks (12' and 8') out of 3/4" plywood, with no fancy joints, just butted, glued and screwed together. I then covered in interiod with PVC sheeting - this stuff in extremely tough, and will easily stand up to photographic chemicals. It's not cheap, and the cement used to glue the sheet down is very harsh, but I'm glad I did it. Unlike epoxy, which can crack over time if its stressed (it's better/stronger if you use fibreglass mesh with it), PVC will never crack. PVC is somewhat flexible, and when glued together the pieces of PVC are physically joined - they ain't coming apart, noway, no how. I've tried to pry apart some test pieces; no dice. When glued with the correct solvent/cement, two pieces physically become one.

I mentioned Sintra--it hasn;t been my experience that it scratches easily--but like I said, we use it where I work for signage & silkscreening & some exterior casework. I know it will ding up for example--dimple--if you pound on it with a hammer....but for the most part, it seems to a very durable exhibtry material. again--like I said--my only experience with it as far sinks go is in using as a duckborad in a stainless steel sink. For this, it has worked very well....ymmv.

Well, I wound up doing it exactly the way Al Kaplan said, using polyester resin and glass cloth. It was messy and gooey, and the laquer thinner I used for cleanup smelled worse than the resin. I still imagine I can smell it, a week later. I didn't do the world's neatest job, but it doesn't look half bad, either. And it's DONE!

 

The fellow at Porter paint said there's no paint equal to the job, whether epoxy, urethane, or whatever. He said I should use Klenk's epoxy. But that appears to cost four times as much as the polyestrer resin, so I passed on it.

 

Thanks to all, especially Al.<div></div>

Let's try that again, a little smaller. . .<div></div>