Hard rubber repair

juan · Jul 31, 2019

i have a couple of 4x5 hard rubber tanks with cracks. I’ve patched similar cracks in the past by filing out the crack and putting in JB Weld. Does anyone have any experience making these repairs with other products?

AgX · Aug 1, 2019

I would use epoxy cement of the slow curing kind. And I would not even consider another cement.

Why are you considering another one? Chemical resistance?

BMbikerider · Aug 1, 2019

If you don't mind the look of the finish, a quicker repair and one certain to work is the silicon sealer used to waterproof the edges of baths, shower basins etc. I would use the Automotive type, it is stronger and is proof against fuel, oil, battery acid, etc etc. Left overnight it will be ready to use in the morning.

Scrape back a small groove along the crack to give the sealer a better chance of holding on both sides, apply a small amount and wipe upwards along the crack to finish off. Use an old credit card which will give a nice straight edge. If the tanks are black, you can get black sealer that will match in and make the repair less visible

jim appleyard · Aug 1, 2019

I've used epoxy on my tanks. It worked well for a few years, but it needs another repair. Not a hard or expensive job to do again.

juan · Aug 1, 2019

Thanks. As I said, I've used JB Weld before - that's an epoxy. It's lasted about a dozen years and shows no signs of needing further work. I haven't had good luck with silicon. It stops the leak for a short time, but lacks the strength for a long term solution. I was just wondering if anyone had a good experience with anything new.

BrianShaw · Aug 1, 2019

What about a “tar” like Henry’s roofing compound, or the like.

jim appleyard · Aug 1, 2019

My dad used to like Gorilla Glue, but I know nothing about it. Anyone else?

Backin the days when I was a skier, I used to fill gouges in the skis with a P-tex (sp?) pencil. It was the size and thickness of a pencil, but made of some kind of plastic. You would light one end with a lighter, get it burning and drip the molten plastic in the gouge. Takes a bit of care, and I would only do this outside as the fumes are nasty, but the repair lasted forever on a pair of skis. I guess it would last double that on a film tank that sees no real contact from anything else.

jim10219 · Aug 1, 2019

JB Weld is probably your best bet (or another 2 part epoxy like PC-7 or something similar).

Gorilla Glue is great for some things, but it expands as it cures and leaves behind a huge mess of rock hard foam. It also might not seal up the cracks fully like an epoxy would due to the formation of air bubbles. Now, Gorilla Glue does make a 2 part epoxy that might work, but it's not the same thing as the glue they're most known for.

mshchem · Aug 1, 2019

My Dad had 1940's era Ace hard rubber trays. He chipped one, repaired with epoxy, held for a long time. I still think for 4x5 black and white hard rubber tanks are hard to beat .

DREW WILEY · Aug 1, 2019

Roof tar? Great idea. Good film DMax, perhaps with no image left, and carcinogenic goop all over your fingers. Try it on a moonshine tank first and see how long your hooch customers live. But what do I know? I only sold truckloads of Henry's products at one time. Forget Gorilla glue too. It's great on wood, miserable on plastics. Here's what to do: first you have to determine if your material can be cemented or not. Take a rag and some acetone and see if that conspicuously hazes the rubber or plastic or whatever it is. If it attacks the material, it can be solvent welded; if the acetone is inert, the plastic or rubber itself is immune to ordinary glues. Things like ABS plastic can be solvent welded with multi-purpose plastic plumbing pipe glue. Older thick plastics like bakelite seem to accept marine paste epoxies well. Don't use those five minute kind. JB Weld is a widely available semi-paste and versatile; but don't rush it; give it several days of cure time before immersion.

bdial · Aug 1, 2019

jim appleyard said:
My dad used to like Gorilla Glue, but I know nothing about it. Anyone else?

Backin the days when I was a skier, I used to fill gouges in the skis with a P-tex (sp?) pencil. It was the size and thickness of a pencil, but made of some kind of plastic. You would light one end with a lighter, get it burning and drip the molten plastic in the gouge. Takes a bit of care, and I would only do this outside as the fumes are nasty, but the repair lasted forever on a pair of skis. I guess it would last double that on a film tank that sees no real contact from anything else.

Gorilla glue is a polyurethane glue, it bonds well to lots of things, and cures by reacting with moisture in the air or in what you're gluing. It's not as strong as some alternatives, for example, epoxies. As mentioned, it foams as it cures and the foaming can make a big mess, it can also force the items you're gluing apart leading to a weak joint. After curing, it is waterproof, which would be a good thing for the OP's application, but I think an epoxy would work better, it's also waterproof, stronger than polyurethane, especially if there are gaps in the fit of the pieces that need to be filled.

David A. Goldfarb · Aug 1, 2019

Hard rubber tanks are abundant and cheap, or they used to be when I was in the market for them, though they’re heavy and can be costly to ship. I’ve accumulated enough not to worry about repairing them, using the cracked ones to store film hangers or use as dry tanks to hold loaded hangers before transferring them to the developer.

john_s · Aug 1, 2019

JB Weld yes. The problem with silicone is that there are lots of different ones and most of them don't adhere well. I regard them as good gasket material only.

DREW WILEY · Aug 1, 2019

Polyurethane glues need a fair amount of tooth - more than just sanding - to work well. Some phenolics or Bakelites (including certain types of Garolite) contain internal fabric or paper compressed together, and glue well with polyurethane glues; other types which are too dense do not do well. Gorilla glue spreads laterally better than the others; but all need to cure under pressure. And all are humidity-activated, another complication if the surface is too hard to retain moisture in advance. I tested early versions of several of these brands before the general public knew about them. Epoxies are their own topic. I won't go into detail; but in the shop I keep on hand for sake of various darkroom repairs PC11 Marine paste epoxy (light color when mixed), PC7 (gray paste), JB Weld, and Devcon 2-Ton Epoxy. I also have various waterproof industrial caulks which are not likely to be found in the average hardware or paint store.

Hard rubber repair

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