Fiberglas Darkroom Sink Question

[Kevin Crisp]

For those of you who have done this, could I get away with resin over plywood, with mat/tape in just the seams, or should I have Fiberglas mat over everything? Thanks.

[bob carnie]

Kevin

I use West Systems over plywood and have made many sinks that work well.
Very simple odourless and goes on like paint.


Bob

[dsphotog]

Yes, one of my sinks is 3/4" plywood coated with resin inside, (painted outside) only the seams are reinforced w/ fiberglas fabric.
I used brass screws & glued all the seams too. Very strong!
Oh, put in the drain before you apply the resin.

[Richard Wasserman]

Yes, one of my sinks is 3/4" plywood coated with resin inside, (painted outside) only the seams are reinforced w/ fiberglas fabric.
I used brass screws & glued all the seams too. Very strong!
Oh, put in the drain before you apply the resin.

That's how I did it. My current sink is over 20 years old and never a problem.

[rdenney]

I agree with Bob's recommendation to use the West System materials. Regular polyester resin used with home-laid fiberglass is not all that waterproof in the long run, but the epoxy resin used in the West System is. I would probably put a layer of fabric everywhere to prevent future cracks, but I think just doing the seams would probably be fine.

Rick "who prefers fabric to matting just for ease of application" Denney

[Henry Ambrose]

Yes, you can tape only the seams, but it is better to apply a layer of thin fiberglass cloth and two coats of resin over the plywood before you cut out your pieces. With your plywood laid flat you can get a nice surface build up. The resulting film thickness makes your sink really waterproof. The surface finish will be very smooth which is nice for clean up every time you use it.

I apply the resin with an adhesive roller then lay the cloth down on top. Let it cure and then the second coat goes on with a roller as well. When you assemble the parts, leave a small filet of resin in the corners and you're done - no tape needed. And yes, West System is great stuff. If you start in the morning and pay attention to the technique and timing you can finish the sink in one day.

On the other hand, lots of folks have built plywood sinks with yellow glue, slapped a couple of coats of paint on them and used them for years.

[Henry Ambrose]

To get the sink to drain well I put a little draft in the bottom at assembly. At each end I add a ledger of 1" material that the bottom panel sits on. I then apply resin and nail each end with my nail gun. Screws work fine if that's your preference. Then while standing in the sink at the middle, I shoot in the sides. The result (on an 8 foot sink) is a drop of 1/4 per foot to the central drain. I hope that explanation makes sense, if not, I'll draw to clarify on request.

[Henry Ambrose]

For the drain I use a hole saw to cut a hole that about the right size for the drain. If you don't have that big hole saw, use a jig saw to carefully cut a round hole. Dress up the hole with a rasp to make it nice. Then find the router bit that will give a profile that's close to that of the drain and make a cut that lets the drain recess into the bottom panel of the sink. Fit it all up and bed the drain with resin. Wax the drain so you can knock it out after bedding. Alternately, just glue it in with resin if you don't care about ever taking it out.

[Ron McElroy]

I used an expoxy paint on mine and they are still waterproof after18 years. The seams were lined with fiberglass tape before painting the sink. I finished the drains much like Henry.

[Kevin Crisp]

Thanks for all your helpful comments.