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How To Build A Darkroom Sink
Before We Start
I'm going to teach you how to build a darkroom sink. What I'm not going to do is throw a bunch of confusing choices at you. Especially choices of materials. Well, maybe just a couple. I know how I built my sink and this is what I will guide you through. I hope I can inspire you and give you the confidence to build your own - that is if you're in need of a sink, but not real, real soon. Otherwise you're going to have to buy one. Of course, you actually are buying one here but in pieces that you put together from your own custom measurements.
Now - your space. The obvious thing right off is that you'll need to put your sink in a room or area where you have access to hot and cold running water and, of course, a drain. I'm not going to get into plumbing in this article. Except to say that you'll want to drill the drain hole in the end of the sink bottom closest to where the drain is located. I'm thinking here, for example, of a sink location in a basement near the laundry tub drain. Or if you're fortunate to have space for a sink in a room adjacent to a bathroom where you can tie into the plumbing in the common wall. Ideally, the drain hole should be at the far right back corner of the sink bottom because that's where the print washer will be and because that's where they usually are. The sink will be made and/or installed to drain to that corner.
We'll be building a plywood and pine wood sink. Before I get into a list of materials and tools I want you to consider where you're going to put the sink after it's made. This will determine the length and width and, to some extent, the height of the sink. By the way, speaking of height you're going to need a sink stand. You know - something to set it on that is strong and sturdy and capable of holding a certain amount of water and other liquids like developers, stop baths, fixers and print washers in the form of trays and /or tanks. This could add up to a lot of weight. You're also going to be leaning on the edge of the sink during your processing procedures sipping your coffee or cheap red wine while waiting for your prints to develop. You don't want the thing teetering and swaying around. I'll talk about the stand in a future hub.
MATERIALS AND TOOLS
Materials 1 - 8'x4'x3/4" sheet plywood, sanded on one side. 2 - 6'x10"x1" Whitewood (Pine) boards. (Actually 6'x9"x3/4" See explaination below). 1 or 2 tubes wood adhesive. 1 - 100 piece box Zinc plated flat head Phillips screws 8 x 1-1/4. 1 - Tube white window calking. 1 - Bathtub size drain fixture. 1 - QT Steelcote brand epoxy paint (various colors avail.)
Tools Tape measure, Note pad, Phillips head screwdriver or Phillips head drill bit, Electric drill w/set of bits, Hammer, Hole saw set.
Get a tape measure (this is the first tool you'll need) and measure the spot where you want your sink to sit. Remember - near a drain pipe you can tap into and hot and cold water pipes. Most darkroom sinks are at least 6 ft long. Mine is 9 ft. (scroll down to the very end of this article for a couple photos of my sink ) I sometimes wish I had a 10 footer but the space only allows for a 9 footer. A 6 ft sink will comfortably accommodate 3 -11x14 processing trays and a print washer. You can make the sink as wide (front to back) as you want but at least 2 ft is best. Mine is 21/2 ft. A rule of thumb is to make as big a sink as you have room for.
A little tip here; I cannot stress enough the importance of keeping notes. I like a spiral 5x7 pad for keeping notes and measurements and drawing diagrams. It's also the right size to take to the lumber and hardware stores to make sure there's no mistakes trying to buy from memory. In fact, you may want to print this hub and tape it into your note pad.
Back to measuring. Lets assume you're going to have a 6 ft long x 2 ft wide sink. Now you have to decide how deep you want the sink to be. Mine is about 9 inches high. You've probably seen sinks that are shallower - 2 to 6 inches. I used to make prints in trays that were just arranged on a kitchen counter top. I have several shirts with developer stains on the front to remind me of that kind of set-up. There's going to be a certain amount of splashing no matter how careful you are. Those of you who have worked in a darkroom before already know this. For my way of working, about 9 inches deep seems comfortable. So our sink is going to be 6' x 2' x 9" and made with 3/4" thick plywood and pine. This is going to be a heavy sink! All the better.
Off To Home Depot (or someplace like it)
Plywood comes in sheets of 8 ft x 4 ft. It also comes in basically 3 thicknesses -- 1/4", 1/2" and 3/4". We want the 3/4". And you have a choice of "sanded on one side" or not sanded for non-cosmetic construction uses. (Also available is plywood that's "treated". This means water and weather proofed for outdoor use and is considerably more expensive.) We want the "sanded on one side" for a nice smooth sink bottom. You have to buy the whole sheet unless there are scrape pieces in the scrape bin that you can use. You might get lucky and actually find 2 sheets of 3/4" x 6' x 2'. That's right - 2 sheets of 6' x 2' which is what you'll get from 1- 8' x 4' sheet with 2 - 2' x 2' squares left over.The 2 sheets of 6' x 2' plywood are going to be screwed and glued together to make the bottom of the sink. One of the 2' x 2' squares will be cut into 2 - 2' x 9" planks for the ends of the sink. The other square can be used for a shelf or two above the sink.
The good news is that you don't have to struggle with a full size sheet of plywood because you can get it cut down to the size you need. Right there in the lumber dept. You'll be charged so much per cut - usually about $1. So have your measurements with you in your notebook and preferably with a diagram you've drawn of the sink you want to end up with. Show it to the nice man making your cuts. All this saves you the cost of buying a circular saw and risking your car going airborn on the freeway with a full sheet of plywood straped to the roof. If you don't think the 6 x 2's will fit in your car, get somebody with a bigger car. I wouldn't strap these to the roof either.
For the front and back we'll use two boards, each measuring 3/4" x 9" x 6' 1-1/2". You'll need this extra 1-1/2" longer than the sink bottom. I'll explain why when we come to fitting everything together. The lumber store I go to calls them 'Whiteboards', but I think they're pine. Lumber stores use a weird labeling system. In other words, you're not getting what you think you're getting if you go by the labeling. For example; what they call a 2" x 4" is really a 1 1/2" x 3 1/2". And so a 1" x 10" x 6' is really a 3/4" x 9" x 6'. Which, for our purposes, is almost perfect. It'll have to be longer by 1-1/2" which means you'll have to get longer boards (maybe 8 or 10 footers) and cut them down to 6' 1-1/2". Take your tape with you to the lumber store and measure those boards. And sight down the length to make sure they're not warped. Do the same with the plywood sheets. Make sure everything is absolutely flat. While you're there, get the screws, wood adhesive and calking.
Ok, you're back home having transported your plywood and pine pieces in your car and not on your car. We're going to drill the drain hole first before we start putting the sink together. And you've managed to borrow or steal a drill by now. The hole is going to be in the back right corner of the bottom of the sink --- remember? But first lay one sheet of sink bottom plywood on the floor, sanded side down, and apply long ribbons of wood adhesive along all edges and then in any irregular pattern you want up and down and back and forth.
Follow the directions on the tube about drying times, etc. Lay the other sheet on top with the sanded side up making sure all edges are even with the bottom sheet. At this point it would be wise to either clamp the two sheets together or drive a couple nails through both sheets to keep them from sliding out of alignment with each other. Now start drilling in your screws. Put one at each corner about an inch in from the edges. Then along the edges about 6 inches apart all the way around. It's up to you how many more screws to put in the rest of the board - maybe 10 or 20 more. Enough to keep the center from bowing if the glue somehow doesn't hold after 20 years. By the way, this is the underside of the sink bottom. The screws shouldn't go through the other side. It'll be nice and smooth with no screws showing because they're only 1-1/4" long going into two sheets of plywood 1-3/4" thick.
Pick the size of hole saw blade for the size of the drain fixture and attach to your drill. About 3 - 4 inches in from the right corner of the sink bottom, drill the hole. It may not cut all the way through but the pilot drill bit will go through to the other side. This will be your guide when you flip the bottom over and finish cutting the hole from that side. If you want to recess the sink drain lip around the edge of the hole, you'll have to cut away the wood with a sharp utility knife. About 1/8" should do it or enough so that the lip surface is even with the sink bottom surface. Again - follow the installation instructions included with the drain fixture. Install the drain using enough plumbers putty or calk to seal the drain fixture in the hole. There's a locking nut on the under end of the drain that draws the fixture down for secure seating.
After installation and enough time for the calk to set and dry, run another bead around the edge of the recessed lip and smooth it nicely. Be careful not to knock against it while putting together the rest of the sink. You don't want to be breaking any seals that could leak later.
OK. You've got the the sink bottom sheets glued and screwed together and the drain installed. This would be a good time to check the surface of the sink for any roughness - even though this is the sanded side. Wrap a sheet of fine grit sandpaper around a small block of wood and sand the whole surface smooth. All your pieces are cut to fit on the back, front and sides of the sink. You're going to attach them with the screws you bought. I suggest here to pre-drill the screw holes for a couple reasons: You'll see exactly where the screws are going and they'll be a lot easier to screw into the sink bottom edge if the tip of the screw is already through the wall screw hole from the start.
Now, you want the screw holes to be just a tad smaller in diameter than the screws - just enough for the screw threads to "bite" into the sides of he hole. Some screws could possibly, with effort, be pushed through the hole with a strong thumb. But you don't want that. Stagger the drill holes so that you'll be screwing into both sheets of sink bottom. In other words - every other screw will go into the top sheet and every other screw will go into the bottom sheet. Drill those screw holes along the edges about 3 - 4 inches apart.
After all the holes are drilled, you'll want to "dry fit" the pieces together just to make sure everything fits like they should. A friend to help you with this may be necessary. Now to sum up before we start putting this thing together. You've drilled screw holes along all bottom edges of the front, back and side walls. You've also drilled holes up the right and left edges of the front and back walls for screwing into the butt edges of the side walls. As I mentioned before, in order to do this, the front and back wall boards will have to be 6' 1-1/2" long - extending 3/4" longer on each end than the actual sink bottom.
Before you start attaching the front, back and side walls, run beads of adhesive along the edges of the sink bottom and side walls. Now start drilling in the screws. Even though you've previously "dry fitted" the walls, put in only a couple screws near the ends of each wall or panel just to make sure the fit is right. Wipe off any excess adhesive that might have oozed out while driving the screws in. Now run beads of the calking along the inside edges where the panels meet the sink bottom. Run your finger along the beading to make sure it gets pressed into the crack seam. Smooth out any excess calking along the seam. It wouldn't hurt to run some calking up the side seams too. Leave the sink alone for a day or so to let the calking set and harden.
Now you're ready to paint the sink. Prepair the sink by sanding any rough spots and dried calking. Vacuum the inside and wipe clean with a rag moistened with a little paint thinner. Steelcote Epoxy paint is an industrial product for many different applications. Mostly for coating floors of factories, office and warehouse spaces, school gymnasiums, swimming pools and chemical holding tanks. The stuff dries steel hard and wears very well. It's a 2 part mixture and dries over-night. I've used the medium gray color for my sinks, but there are other colors to choose from. Follow the instructions on the can. You can also choose to apply a second coat right away if you think your sink is in for a lot of use. I've re-applied Steelcoat to my sink every 2 or 3 years.
Congratulations - you sink is done. Well - almost. The front edge you're going to be leaning on with your forearms while waiting for your prints to develop needs to be wider for comfort. Like a couple of inches or more. Get a couple lengths of 1 x 2 x 6 pine wood and nail them to the top and front edge of the sink, sand smooth and finish them off with a coat or 2 of polyurethane varnish. You could even glue on a long strip of soft rubber for even more comfort. Now you're done! Good luck with your darkroom sink. I'm sure it will last for many years.