Question for WOODEN darkroom sink users only : LUSENET : Large format photography : One Thread

Hi all,

Am considering a wooden darkroom sink and need advice on what products to use. I assume plywood for the wood. Any special type?

What type of caulk should I use and do you caulk before the "paint" coating?

As for the "paint", what are the best types of products? I will have valuable material stored underneath the sink so don't want ANY leakage. I don't want to use fiberglassing or plactic sheeting, just a waterproof coating of some kind.

Lastly, does the "paint" have to be reapplied every so often and if so , how often?

Thanks for any help you all can give me . . .


-- Scott Jones (, April 22, 2002



I built my sink about 4 years ago and it hasn't leaked a drop. I used normal 3/4 inch A/C plywood and rabetted the bottom into the sides. I used West System epoxy to seal it. I used the epoxy thickened with slica to form a fillet at the bottom-side joints, then painted two coats of unthickened epoxy on the whole inside surface. West System is mainly used for boat repairs and can be purchased from most marine hardware dealers. It comes in two parts which you mix to form the epoxy. It is a little expensive but worth it.


-- David Walker (, April 22, 2002.

Scott I built my wooden sinks out of 3/4 inch particle board for the bottom and 1x6 for the sides. To build them today I would us MDF for all the wood parts. I used fiberglass tape to go around all of the seams before painting. This allowed me to round out the 90 degree corners. As for the the coating I believe any 2 part epoxy paint will work. I put 5 coats on mine and have only had 1 leak in 10 years. Not a dripping leak, but enough of one to swell the wood at one of the drains. Some epoxy and 2 coats of paint fixed that.

The beauty of wood sinks is the ability to easily custom fit a space, but beware. If you build the sink in place before painting wear a respirator and have plenty of ventilation.


-- Ron McElroy (, April 22, 2002.

hi scott you might consider marine plywood as well, they say that it will hold up better .. when i had a wooden sink it was never painted, just fiberglass resin & resin with "cloth" when it was rotted out and needed to be repaired ( after 20+ years of use) . good luck!

-- jnanian (, April 22, 2002.

I used 5/8 inch plywood, regular old silicon bathroom caulk (if I recally correctly), and swimming pool paint. 2 years and counting. I'm sure it will need a fresh layer of pain within a couple years, but big deal. (though the paint is kinda nasty and its best to use outdoors or in a garage)I'm very happy with it because I custom shaped it to fit my L-shaped workspace and if I ever need a bigger sink I just knock down a side and add onto this one!

-- Wayne (, April 22, 2002.

Epoxy, young man!

I used 3/4 BC exterior plywood, cut the parts to size, coated the parts with a layer of glass cloth on the inside and 2 coats of West System epoxy on both sides. I then fit the parts together using just enough screws to hold it together and added epoxy resin to the joints as I pulled them tight with the screws. After that cured, I removed the screws, filled and sanded the holes and then applied several coats of epoxy with pigment added for the final finish. For the drain, I cut a hole with a jigsaw, rasped it to a loose fit for the flange on the drain and then bedded the hardware in the recess. This took place over one weekend in warm weather. This may be overkill for some folks. If you don't care what it looks like just screw the sink box together and give it a couple of coats of epoxy. Either way its probably under $100 and may outlast you.

-- Henry Ambrose (, April 22, 2002.

Fifteen years on a plywood sink covered with fiberglass and epoxy. Used fiberglass sheet and mixed epoxy just like that for a fiberglass boat. Still works fine. The only problem is that the wood has warped some over the years so now the drain is not quite at the lowest point in the sink.

I might suggest a product called Durham's Rock Hard Water Putty (honest) as an equivalent product for avoiding the 90 degree angles between the walls and floor of the sink.

-- Joe Lipka (, April 22, 2002.

I used 3/4 ext ply, and then took it to a speed shop and had them apply spray-on truck bed coating. The coating is very durable, temp/chem resistant, and looks so good most folks think I had the sink custom built. The coating was $120, and saved hours of hard work and nasty fume

-- Bruce Pottorff (, April 22, 2002.

Regular 3/4"plywood purchased at Home Depot, caulk with any waterproof caulking (also at Home Depot), paint with Moorelastic sold by Benjamin Moore. Apply about four coats initially (it's very easy and quick to apply - coating the interior of my 8' x 2 1/2' sink takes about ten minutes). I recoat about once a year just to be on the safe side. A one gallon can costs about $25 as I recall and will last a long time. I've probably applied ten coats from the beginning and I'm still using the original can. I'm sure there are other products that work equally well but this one is easy to find, easy to apply, and relatively inexpensive considering how long it lasts. One point about building the sink that's easily overlooked. Put the drain at one end of the sink, then make the legs on the opposite end a little longer (I think mine are a half inch longer) than the lens at the drain end to facilitate draining.

-- Brian Ellis (, April 23, 2002.

Hi, I recomend A/C plywood, with the good side (A) facing into the sink. 3/4 inch wood with good support if the spans and panel sections are large. WEST system epoxy should be used to coat the wood on all sides and surfaces. This seals the wood, preventing it from breathing and absorbing moisture. If it is coated only on one side, the other side breaths, swelling and contracting. This can lead to cracking, spliting, and rot. Generally it takes 5 coats of epoxy to waterproof. The first and second coat are all that is needed before glassing. After glassing then I would apply 5 coats. (unthinned). The coats microscopicaly look like swiss cheese. By the time five coats are applied, the probability of holes lining up and allowing a leak, is nil. After the first coat is applied, then the other coats are put on by brushing a little on then use a autobody putty squeegee to spread it very thin. The first coat on the bare wood can be thinned with laqeur thinner at around 25%. This helps it to absorb into the wood, creating a stronger bond. Lightly sand when dry. Note: if the dried epoxy feels greasy or clogs the sand paper then it will need to be wiped off with water and then dried. I use cheap paper towels. One to wash/wet, one to wipe dry. Sanding is not necessary between coats if the previous coat is still tacky. (able to leave a finger print.) Fillits, (rounded corners) can be made in the sink using body putty or micro balloons. This should be done after the first two coats of epoxy have been applied. Micro balloons is like a thickener that sands easily. (purchased where you get your epoxy.) When mixed with the epoxy it should be thick like mashed potatoes. (no drips or runs.) The color is very dark brown. Gob this stuff into the corners and draw a piece of PVC pipe down the seam so that it touches the side and bottom at the same time, leaning it in the direction it's going. This should only leave micro balloons in the corner itself, and it should be cove shaped. The diameter of the pipe determins the radius of the corner cove. It is at this point that 10 ounce fiberglass cloth can be applied. If you don't want to glass the sink, then apply five more coats of epoxy, each coat to be applied when the previous coat is firm yet allows a fingerprint to be left in the coat. When finished, clean it with water and paper towels. Dry and sand any rough spots to your liking. I paint with exterior latex paint. Epoxy paint is better, but cost alot. If you want to glass the surface, then cut the cloth to fit the bottom and come up the sides a couple of inches. epoxy the area to be glassed with a roller made for resin. (very short Knap, or foam). lay the cloth in and get out all the wrinkles. Wear latex gloves and use your hands to make sure the cloth is smooth and pressed into the resin. More epoxy may be needed and applied by brush to coat the cloth until its saturated and appears clear. Use the bodyputty squeegee to squeegee all excess resin off the cloth. When the cloth is tacked, (firm), then apply another coat of epoxy. Continue the application process until the weave of the cloth isn't felt. You can apply thick layers but be careful to not apply too much at a time. It will level itself and you won't have a low end for drainage. Do not pour in the epoxy to fill the weave, It will flow and level itself. If you built your sink with the bottom angled towards one side for drainage, you'll lose it by appling too much at one time. The top edge of the glass cloth should be sanded smooth to your liking. The rest of the sink should now be given five or more coats of epoxy if not already done so. sides can now be glassed in the same manner if you want, overlapping the seams. After all this is done, then cut in the drain hole. Before installing the drain piece, coat the edge of the cut with epoxy. Use GE brand 5200 caulk for anything to be caulked. It's expensive and perminent. The glass cloth adds a lot of stregnth to the system, and can take lots of abuse. However I also think that a strong sink with good base will be ok with just epoxy coatings. I learned this stuff working in a custom boat shop for a few years. Use common sense when using tools and chemicals. wear a dust mask when sanding. Building a sink using the above methods will give you the mother of all sinks and outlast your house. I built mine with tempering bath areas, multiple faucets, ribs in the bottom, and a deep sink at one end for washing. 16 x 20 trays sit inside, 20 x 24 hang by the lip of the tray on the sink edges. I have around $200 invested. (I already had the glass cloth.)

sorry for the long winded post, and bad spelling. Hope it helps people build their dream sink. dee

-- dee (, April 27, 2002.

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