Restoring a fiberglass(?) sink

Michael R T · Sep 28, 2023

I've found a sink that looks like it would be a good fit for my in-progress darkroom. The only thing is that it's a bit of a mess, as it was apparently in a garage or barn or something for years:

It doesn't seem to have any holes or cracks, though, and it's a good price ($40). Does anyone have any advice on cleaning this up? It looks like it may be fiberglass, as the bottom has that kind of rough texture to it.

Or are there any potential issues I should look out for?

I did some research on maintaining fiberglass, and there's lots of stuff for RVs and boats, mainly talking about waxing to keep them shiny. Not sure if the same things apply to darkroom sinks.

Whatever is on there is pretty caked on, but it seems to lift with some scratching. I did read that abrasive cleaners should be avoided on fiberglass, though?

jeffreyg · Sep 28, 2023

Check with a marine supply. Forty-eight years ago I lined a custom built plywood darkroom sink with marine polyester and fiber glass reinforcement. It is still going strong with no leaks. I m sure they can advise you

Kino · Sep 28, 2023

I would test some CLR or Lime-A-Way for cleaning. Both products claim to be safe to use on fiberglass.

Might have to soak it for an extended period to get the grime to dissolve. Do it outside; who knows what that gunk is and how it may react to an acid based cleaner?

You may not need to repair it; clean it first to see if it actually is damaged.

mshchem · Sep 28, 2023

Mr. Clean magic sponge! Careful with chemicals. I wouldn't worry about bad stains just get rid of the filth. Looks lovely!

Paul Howell · Sep 28, 2023

Many products on Amazon.

ags2mikon · Sep 28, 2023

Vinegar, CLR, fiberglass is okay with mild acids. Just make sure you wear your PPE.

Hilo · Sep 28, 2023

Before you do anything, my main worry would be how to photograph it.

MattKing · Sep 28, 2023

Hilo said:
Before you do anything, my main worry would be how to photograph it.

For me, the main worry would be explaining to my spouse why I was bringing THAT home with me.

Once it was cleaned up, no problem.

Don_ih · Sep 28, 2023

It's quite possibly something known as "composite" and not fibreglass at all. Fibreglass would be a gel-glaze with visible fibre striations on the underside of the sink. Composite would be more evenly textured on the underside. As dirty as it is, you can't actually determine the integrity of the glaze if it's fibreglass. However, if it's composite, short of having a hole in it, it will be fine under that dirt.

runswithsizzers · Sep 28, 2023

Technically, "fiberglass" refers to the dry, flexible material made of glass fibers. The term "fiberglass reinforced plastic" (FRP) more accurately describes what most people simply call fiberglass. FRP is made by embedding glass fibers in some kind of resin. When strength and light weight are important, layers of woven fiberglass cloth are laminated, and the minimum amount of resin is used. When low cost is more important than strength or weight, the glass fibers may be chopped and sprayed into the mold with the wet resin.

"Composite" means something made up of two or more things, so fiberglass reinforced plastic is a type of composite. In boatbuilding and the manufacture of many items like high performance bicycles, etc. the word "composite" is often used when the laminate contains additional fibers like carbon fiber or aramid (Kevlar).

There are several different types of glass fibers used, but if your sink is FRP the chemical composition of the glass fibers will not matter. There are also several different types of laminating resins, and if your sink is not waterproof or needs structural repairs, then it might matter which resin was used.

***Avoid strong solvents like acetone / lacquer thinner, etc.***

So clean it up, see if it holds water, and report back. If repairs are needed, we can try to figure out the best way to procede.

runswithsizzers · Sep 28, 2023

Michael R T said:
It looks like it may be fiberglass, as the bottom has that kind of rough texture to it.

Does the texture look like woven fabric (like burlap)? Or are you seeing randomly positioned fibers (like a furnace filter)?

DREW WILEY · Sep 28, 2023

Get some green Scotchbrite pads and one of the cleaners recommended above, clean it up, and then see if it is worth keeping or not. Fill it with water and test for leaks. Because there are sunken horizontal reinforcing channels which are horizontal to the length rather than parallel, it looks more like an agricultural trough than an actual darkroom sink, and is probably not fiberglass at all, and perhaps thermo-moulded styrene or Sintra. Then there's all that failing caulk-like goop around the inside of the perimeter which might be a real headache to remove and redo. The next endless challenge for Sisyphus? You might end up spending more by the time you're finally done than something comparable new.

Hassasin · Sep 28, 2023

First give it a good power wash. Then take another photo.

Snoop · Sep 28, 2023

jeez people, fiberglass is the common general name for whatever made of some resin and any sort of matting... everyone gets what the animal is...
for now its just made of fiberdirt
The biggest issue is that it can make a mess wherever you clean it, end of the driveway is probably your best spot.
Harsh solvents can ruin it, and bleaches and industrial degreasers can make more difficult the repairs or recoating later on, elbow grease is safe enough. (for boats we used drill attachments, they are fast but they arent cheap and that sink is not that big)
Warm water and a stiff brush should take off most of the gunk, after you can add some baking soda and soap paste to help scrubbing, (if u powerwash it use the flat nozzles not the turbo one which can be too strong)
Its possible that some of the dirt actually stained it, stains can eventually be fixed with some light abrasive paste if they really bug you but dont try to go nuts bleaching a spot.
When its cleaner you can better judge materials and conditions, know that anything "fiberglass" is easily repairable unless the whole thing is rotten (if it is u will know it right away, pushing on it will just poke an hole through). If its solid then it becomes just a matter of cost for the materials to fix it up, if it even has something to fix.

brush off the underside too, with all that dirt if there is a thin crack that goes through its likely it will show on both sides as a thin black line

Hassasin · Sep 28, 2023

Hilo said:
Before you do anything, my main worry would be how to photograph it.

If this photo were taken by Andy Warhol, it would have gone straight to MoMA.

Bill Burk · Sep 28, 2023

Don’t clean it. It’s charming.

mshchem · Sep 28, 2023

Yep, stains are patina.

Kino · Sep 29, 2023

Yeech! Looks like an autopsy table from the Black Death Era...

DREW WILEY · Sep 29, 2023

Maybe some of that black asteroid dust they broke off made it here on its own, outside the containment capsule. No telling what kind of mass epidemic will happen if you try to scrape that black stuff off. Better read some Asimov first.

wiltw · Sep 30, 2023

If aesthetics bother you, you can coat with epoxy paint, like what you can use to paint garage floor concrete
Cracks can be filed with clear epoxy resin such as is available for laying up boat hulls...you can also bond fiberglass patches to reinforce cracks.

Keith Pitman · Sep 30, 2023

Hard to tell in its current state, but I think it’s ABS plastic. As someone said, give it a powerwash and post another picture.

DREW WILEY · Oct 1, 2023

It looks heat-moulded, so ABS is a good candidate.

Michael R T · Oct 3, 2023

Thanks for all the replies! I've been working on finding a friend with a power washer, so I'll get back to you with photos when it's hopefully more cleaned up.

In the meantime, here are some closeup photos of the underside to give you a better idea of what the material looks like:

Under better light, I also noticed the top has a surface layer that is cracking or flaking off in places. In some places, the flakes can be removed, but in others it seems pretty tough and even though it's cracked they can't be pulled off by hand. Is this the glaze of the fiberglass (if that's what it is)?

Michael R T · Oct 3, 2023

Hilo said:
Before you do anything, my main worry would be how to photograph it.

Now I'm paranoid I haven't taken enough photos before I wash it and change it forever!

MattKing said:
For me, the main worry would be explaining to my spouse why I was bringing THAT home with me.
Once it was cleaned up, no problem.

My spouse had to ride in the car with it on the two hour drive back. She insisted on driving, and made me sit next to the sink. Fair enough.

runswithsizzers said:
Does the texture look like woven fabric (like burlap)? Or are you seeing randomly positioned fibers (like a furnace filter)?

Definitely not as uniform as burlap. Looks more random to me.

Bill Burk said:
Don’t clean it. It’s charming.

Ha. Maybe I should display it in my studio as an objet d'art, and find another sink.

Kino · Oct 3, 2023

Hard to tell, but I'm not convinced that the cracking you see isn't just dried-on scale from whatever was left in the sink for ages.

The mystery continues...

Restoring a fiberglass(?) sink

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