Building a PVC sink: another approach

[Chuck S.]

Going through old files, I found a 1989 article I wrote for a long-defunct darkroom magazine on building a PVC darkroom sink. (Predates homepage article by 13 years.) There are enough differences in details between the two approaches that I thought it might be of interest here. I have posted a PDF below.

Major takeaways:

⦁ First, safety. Unless one intends to assemble a sink outdoors, a respirator with appropriate solvent cartridges is essential, even in well ventilated indoor spaces.

⦁ It's a stronger design to think of a sink not as a big broad "U", but rather as a big broad "H" – with short legs. Whether plastic or wood, this has a lot of options for reinforcing the attachment of sides to the bottom.

⦁ It's useful to outline your darkroom on graph paper with cut-outs of the sink or sinks all to scale. Can prevent major problems later on. In my case I wanted a sink large enough to accommodate six 20 x 24 trays for black and white. It was clear that one sink that large could never be moved out of the space, or handled by one man. So I decided on two roughly equal sinks. Since I worked left to right, developer(s) to rinse/holding, the design would have the right hand sink a little higher and draining into the left-hand. Used a small sheet of PVC to make a splash/drip shield to hang between sinks. Would I do this again - having one sink drain into another? Possibly not. It was a neat idea, and it worked fine, but made design, precision required, and installation much more complicated. I'd still go with two identical sinks for that space, touching at the ends but plumbed separately.

⦁ Cementing long seams using the cement can's built-in mop was futile. PVC cement has two contradictory behaviors: it will start to dry at one end of the seam before one gets to the other end. At the same time, since it is hygroscopic, any significant moisture in the air will start to bead up all over the cement. Solid weld is impossible. The solution, after applying PVC primer, was to use a big veterinary syringe to lay down an ample wavy line of cement and then slide pieces back and forth to distribute it until everything began to grab, followed by multiple C-clamps. (Most plastic syringes are nylon or other which are not attacked by PVC cement.)

⦁ I used extruded PVC 'L's to cement sides and bottom together – .75 x .75 x .080 on the inside; 1.5 x 1.5 x 3/16 below. The small ones from Gehr Plastics were a perfect 90° outside, but the big ones from the local supply house were not. One side had to be run through the tablesaw to square it up. Whatever shapes you use, it's well worth making sure that they're square before ordering.

⦁ Speaking of table saws: I worked a trade to cut all the pieces with one of my bigger clients, a cabinet shop who had really big Delta industrial table saws. I imagine cutting 4 x 8 sheets on a small tablesaw or with hand saws is possible, but…

⦁ "Dump troughs": these were not a needless complication. Extremely handy in getting rid of one tray's contents without slopping it into the main sink or contaminating adjacent trays. Would definitely build those in again, but YMMV.

⦁ And yes, there are several places where I was trying to look 'clever' with my verbiage. Cringe-worthy. No need to point them out!


218428, 218427, 218429, 218430

For members who are seriously contemplating a new sink build in the near future, I still have several pristine copies of this issue. PM me.

Finally - I had to sell these many years ago when I moved from Bellingham, WA to Colorado. If anyone in western Washington has seen or acquired these, I'd love to know. Hopefully still used in a darkroom, though I suppose they might be used for gutting fish or potting ferns....

[Chuck S.]

More photos and drawings. Drawings were done on a Mac Plus with MacDraft or similar, so...

Third photo shows removable connection between sinks from below. Fourth photo shows upper sink draining into lower, with bit of the splash/drip shield between sinks.

[Chuck S.]

Drawings in previous post not sharp. See these pdf's.

218437 218438

Also, more photos - drain detail (another similar drain inside dump trough without standpipe) and inside corner detail:

[Conrad . Marvin]

Thanks for this post. It’s very good timing as I was thinking about how to go about once again making a sink. When I made my original sink out of PVC I used it as a liner for a wood sink not knowing how much PVC would expand when using warm water ……..

I have send a PM

[resummerfield]

Very nice! Thanks for posting!

[Chuck S.]

Just checked with GEHR Plastics website.
https://www.gehrplastics.com/

Here are all their grey PVC 'L' shapes:

218553

[Drew Wiley]

Multipurpose plumbing cements are available which do not dry quite as fast as ordinary PVC cement, but there are different kinds of even that. And as far as small shops go, a good rail saw like a Festool will cut it better than any table saw, provided you have the right kind of plastics blade on it, and a long enough captured guide rail. But any such sink should have a reinforcing fillet solvent welded into every sheet intersection and corner. I personally went with a heat-welded polypropylene sheet sink instead, which is chemically inert. But that required help from someone with the appropriate equipment and skill background.

[Chuck S.]

Rail saw an excellent suggestion, but I don't remember (32 years on!) if the shop I used had one. Choice of tools was their call, anyway.

Every joint and corner was reinforced with solvent welded 3/4" L's on the inside and outside for vertical joints, and 3/4" L on the inside and 1 1/2" L underneath for horizontal. Only the dump trough dam had 'L' on just one side, but it was double thickness @ 3/8inch (see dwg). Every L also got a solvent fillet applied to every inch of both edges after set up using the syringe. As you say, every intersection and corner, even if a bit of excess wasn't pretty.

Also, the round top rails were 1/2" schedule 80 PVC pipe. Installed for both comfort and added rigidity. The slots were cut with a dado blade on the table saw, 3/16" for sides, 3/8" for dam. Took two people to feed and pull because pipe really wanted to cork screw going through the blade, relieving (or maybe introducing) stress in the pipe. Probably cut 25% extra to get sufficient straight enough to use. Rails were also solvent welded on with cement applied to top of walls and pipe 'lips', followed by cement fillets applied to edges. Made walls quite stiff, even if only 3/16" plate.

[John Layton]

Your PVC sink looks great!

I do wonder about the perforated (under tray) mat...do you clean this on both sides after use? Looks like there are little "dimples" on outer surfaces which would act as holdoffs between this mat and the sink bottom...possibly helping to avoid trapping of contaminants over time. Otherwise I would worry about this.

[Drew Wiley]

Portable rail saws weren't available in the US 32 years ago. Stationary panel saws were; but the good ones of those are far more expensive (say, $70,000 versus $700). I made my own dedicated panel saw for plastic sheeting prior to using a portable Festool rail saw. But in both cases I had the advantage of inside deals as a pioneering dealer. The correct kind of blade for the specific material is very important. A sink is a fairly elementary project. This kind of gear has been invaluable in many other ways, all the way from making acrylic slot washers to cabinetry for both the darkroom and the house, even precise fabrication of phenolic colorhead housing components, not to mention all kinds of general remodeling applications both indoors and outdoors. For example, being able to fabricate cabinet components on site in the my house in the mountains (now sold) saved me thousands of dollars in gasoline alone versus if I had had to cut and assemble things here using traditional stationary cabinet shop equipment, and had needed use a much larger truck to transport the result. The third benefit of the newer Festool equipment is that's it's far cleaner, being especially well designed for integral Hepa vac hookup.

[Chuck S.]

The sink mats were assembled from Dri-Dek anti-fatigue floor tiles - the same ones seen in the 1st photo in the top post. (https://www.dri-dek.com/) Just rinsed everything - trays, mats, sinks - after every session. No further cleaning required. The tiles on the floor saw rougher service than the ones in the sinks.

[bob carnie]

I had my super large size trays made out of very dense thick grey plastic material, I had someone weld them together with handles and they have proven to be very rugged and reliable... My question is how does one plastic weld ?
I actually never saw the production of the trays, I just had the raw plastic sheet company cut out to dimensions and someone else put them together, I only saw the final product.

[Drew Wiley]

Solvent-susceptible plastics are "welded" by means of a suitable solvent itself. That means they are not simply glued, but that the type of glue actually melts the plastic together if the edges are duly straight, square, and tightly fitted. That is how PVC, acrylic, and ABS sheet is done, among common types of plastic at least, and it is a relatively easy thing to do in an ordinary shop with basic gear. Then there are those "poly" kinds of plastics which are more complexly molecularly bonded and hence resistant to solvent, like polycarbonate, polyethylene, and polypropylene sheets. These require precisely directed heat to melt together into a permanent seal. It's almost impossible to do with ordinary gear like a heat gun. Plastic and lead sheet welders, as well as roofers working with solvent-resistant layers, have special tools for this.

Your gray sheet material was probably Sintra. It's an excellent choice for somewhat larger trays, or smaller sinks, due to its economy, rigidity, thermal retention, and ease of fabrication. But sheet ABS is stiffer and better for thermoforming. Ordinary multi-purpose plumbing cement works fine as the welding solvent for either. I always pieces of these on hand for sake of miscellaneous darkroom projects.

[Chuck S.]

Also looked into "hot gas welding" early on - very briefly. Way beyond the scope of my little project, my abilities, and the budget. (Would have needed an air compressor in addition to welding equipment.). But here's a good primer:

https://www.twi-global.com/technical-knowledge/job-knowledge/hot-gas-welding-of-plastics-part-1-the-basics-056

[bob carnie]

I am now in the market to make a large vertical print washer with 6 large slots using very thick grey plastic, does not have to be see through plastic like the smaller units I have, but I want the same kind of concept as the commercial units I have . In any given day when printing silver murals I can only do about 12 30 x 40's so a 6 slot with them washing back to back would be perfect. I saw a video of clyde butchers technician using a floor model and since I have floor drain near my sink I think this would be a perfect option. I wish I knew the welder now for sure..

When I print Lambda fibres I always get caught with the prints that are larger than my 20 x 24 washer . I end up wasting way to much water trying to do an efficient archival wash horizontally , basically its one at a time

[Tin Can]

DIY Acrylic Aquarium – How to Build an Acrylic Fish Tank Aquarium Easily

https://www.fabglassandmirror.com/blog/diy-acrylic-aquarium-and-acrylic-fish-tank-guide/

Just something to ponder

I bet a Pro is near you

[interneg]

I am now in the market to make a large vertical print washer with 6 large slots using very thick grey plastic, does not have to be see through plastic like the smaller units I have, but I want the same kind of concept as the commercial units I have . In any given day when printing silver murals I can only do about 12 30 x 40's so a 6 slot with them washing back to back would be perfect. I saw a video of clyde butchers technician using a floor model and since I have floor drain near my sink I think this would be a perfect option. I wish I knew the welder now for sure..

When I print Lambda fibres I always get caught with the prints that are larger than my 20 x 24 washer . I end up wasting way to much water trying to do an efficient archival wash horizontally , basically its one at a time

The places that fabricate/ weld the chemical grade polypropylene (or similar) materials into sinks etc also tend to supply the wider printmaking world (screen print washout cabinets, etching baths etc), along with archaeology, conservation and similar labs - those might give you some leads. Richards of Hull is a fabricator that many use in the UK - you'll almost certainly have someone similar within reach of Toronto. Acrylic prismatic diffusion material is apparently the material used for the textured dividers in the Nova washers.

[Drew Wiley]

Bob, one of the problem with Sintra or ABS is that certain mold release compounds have been used, or plasticizer might have been incorporated into anything vinyl-based. It's important to scrub down any components with vinegar or alcohol before developing or washing anything photographic in these. Don't use any kind of strong solvent like acetone because it will attack these kinds of materials, including acrylic. Poplypropylene would be hell to fabricate into anything as complex as a slot washer, since it can't be glued.

The main problem with a huge slot washer versus just an oversized tray for 30X40's is going to be the sheer weight of the thing not only empty, but especially when filled. Not only will it need to be especially well made, but your floor and stand will probably have to be reinforced unless it's concrete to begin with. Vinyls are going to bow outward due to all that pressure. It makes a lot more sense for the outer housing to be welded from stainless steel, and only the dividers and siphon system be plastic. How much does your 20X24 washer weigh filled? A realistically built 30X40 washer of equal print capacity might be ten times heavier when full.

Textured acrylics are available, but prismatic would seem to be a little risky in terms of scratching print emulsions. What I use are tiny little self-adhesive pure silicone hemispherical bumpers (not the vinyl kind). They'll last for decades. Beware of styrene as a substitute for acrylic; it's relatively brittle, especially over time. Sintra can be obtained textured, and will be far more affordable than acrylic for dividers, but will warp a bit in warm water, so it's a good idea if dividers are not too close together, and are also individually removable if needed.

[interneg]

The prismatic surface is single sided - and you put the print in with the back to the textured surface, where it sticks by surface tension. I understand that much of the Nova washer design owed a lot to Ilford R&D input, including the specific texture chosen.

Polypropylene can be welded - and we're not talking solvent welding here - into a more than adequately strong tank - durable enough to be used as an acid dip tank for etching seriously big plates. I suspect however that a suitable fabrication is likely to end up not much cheaper than the big Kienzle washers that are available.

[Chuck S.]

Plastic fabricators serving the metal plating industry might be another source. Lots of big dip n' dunk tanks. Got to be some of those in Toronto.

[bob carnie]

Bob, one of the problem with Sintra or ABS is that certain mold release compounds have been used, or plasticizer might have been incorporated into anything vinyl-based. It's important to scrub down any components with vinegar or alcohol before developing or washing anything photographic in these. Don't use any kind of strong solvent like acetone because it will attack these kinds of materials, including acrylic. Poplypropylene would be hell to fabricate into anything as complex as a slot washer, since it can't be glued.

The main problem with a huge slot washer versus just an oversized tray for 30X40's is going to be the sheer weight of the thing not only empty, but especially when filled. Not only will it need to be especially well made, but your floor and stand will probably have to be reinforced unless it's concrete to begin with. Vinyls are going to bow outward due to all that pressure. It makes a lot more sense for the outer housing to be welded from stainless steel, and only the dividers and siphon system be plastic. How much does your 20X24 washer weigh filled? A realistically built 30X40 washer of equal print capacity might be ten times heavier when full.

Textured acrylics are available, but prismatic would seem to be a little risky in terms of scratching print emulsions. What I use are tiny little self-adhesive pure silicone hemispherical bumpers (not the vinyl kind). They'll last for decades. Beware of styrene as a substitute for acrylic; it's relatively brittle, especially over time. Sintra can be obtained textured, and will be far more affordable than acrylic for dividers, but will warp a bit in warm water, so it's a good idea if dividers are not too close together, and are also individually removable if needed.

Hi Drew
the floor is solid and I would make it to sit about 3 inches off the floor so the drain is usable I need to make sure this is legal with the floor drain. I think the material that I have my sinks made out of would be strong enough I only need 6 slots or 5 slots. I think the inserts could be 3/4 or even 1 inch to stop bowing no matter how warm the water.

[bob carnie]

Bob, one of the problem with Sintra or ABS is that certain mold release compounds have been used, or plasticizer might have been incorporated into anything vinyl-based. It's important to scrub down any components with vinegar or alcohol before developing or washing anything photographic in these. Don't use any kind of strong solvent like acetone because it will attack these kinds of materials, including acrylic. Poplypropylene would be hell to fabricate into anything as complex as a slot washer, since it can't be glued.

The main problem with a huge slot washer versus just an oversized tray for 30X40's is going to be the sheer weight of the thing not only empty, but especially when filled. Not only will it need to be especially well made, but your floor and stand will probably have to be reinforced unless it's concrete to begin with. Vinyls are going to bow outward due to all that pressure. It makes a lot more sense for the outer housing to be welded from stainless steel, and only the dividers and siphon system be plastic. How much does your 20X24 washer weigh filled? A realistically built 30X40 washer of equal print capacity might be ten times heavier when full.

Textured acrylics are available, but prismatic would seem to be a little risky in terms of scratching print emulsions. What I use are tiny little self-adhesive pure silicone hemispherical bumpers (not the vinyl kind). They'll last for decades. Beware of styrene as a substitute for acrylic; it's relatively brittle, especially over time. Sintra can be obtained textured, and will be far more affordable than acrylic for dividers, but will warp a bit in warm water, so it's a good idea if dividers are not too close together, and are also individually removable if needed.

Hi Drew
the floor is solid and I would make it to sit about 3 inches off the floor so the drain is usable I need to make sure this is legal with the floor drain. I think the material that I have my sinks made out of would be strong enough I only need 6 slots or 5 slots. I think the inserts could be 3/4 or even 1 inch to stop bowing no matter how warm the water. As you can see this is the grey plastic I have had success with in past

[Drew Wiley]

Sounds good. Once the sheets are acquired, just as afternoon fabrication job for anyone properly equipped, though I like to see the solvent welds thoroughly cured for about 48 hrs before moving anything like that. Not too hard for two people to handle if the dividers are removable during transport, or even for one person with a handtruck.

[Michael Rosenberg]

Chuck,

Were you refering the article on the LF home page for making a PVC sink? I wrote that up some years ago. My sink is now 21 years old, and still going strong. Never had a leak.

The gray PVC is a chemical resistant material, not like sintra at all.

Regards,

Mike

[Drew Wiley]

All PVC is aromatic solvent susceptible; otherwise, it would be impossible to glue or solvent weld in the first place. But it will be resistant to alcohol and mild acids, and most typical darkroom chemicals. So it differs from poly plastics like polyethylene or polypropylene which have a far greater range of solvent resistance, and which must be either thermoformed or heat welded. After all, that's why most glue is sold in polyethylene containers, and not any kind of vinyl.

Ordinary PVC sheet is Grade 1; the stiffer and more resistant gray version, Grade 2. But you don't want to spill full strength glacial acetic acid onto even the gray product; it will handle common stop bath dilutions fine.

Sintra is expanded vinyl, so not as dense, but fine for many darkroom applications like liners where lower cost is a priority, at the expense of better rigidity. It's main usage is for signage.

[Chuck S.]

Mike,

Yes. And as I wrote, just "differences in details", and some ideas & suggestions that might interest forum members. Not expecting anyone to follow my example to the letter.

Chuck