OT- Any speciality concoction for cosmetic filling tiny cracks in black granite ?

Milacron · Mar 27, 2017

This is on the inside helm station of a 65 foot yacht...couple of hairline cracks in the surface, which appears to be black granite but could be a man made creation that looks like granite for all I know.

Couldn't find anything at Lowes in black but tried some black silicone sealer already on the boat just for the heck of it. Looked pretty good except impossilbe to spread it in the crack without getting too much of it beyond the crack....and then when you wipe the excess with alcohol it wipes out a little in the crack in the process so the end result it still not good.

Seems like the ideal would be a sort of black epoxy applied by syringe tip but dunno really.

APD · Mar 27, 2017

Milacron said:
Seems like the ideal would be a sort of black epoxy applied by syringe tip but dunno really.

5 or 10 minute epoxy mixed with rustoleum gloss black (the brush-on can, not spray).
I've used this recipe for filling floors etc, dries to a nice glossy black.
Mask off the area around the crack.
When the epoxy is partially cured and still rubbery, you could lay a razor blade flat on the counter and slice off the excess.
Both found in the same aisle in Lowes.

SAG 180 · Mar 27, 2017

If filling cracks in granite is anything like filling cracks in cement with epoxy, it will crack beside the line of epoxy not long after you fill it unless the underlying support for the granite is ultra rigid. Flexible black silicone might be better if the granite rests on a wood base on a boat that flexes a bit when at sea.

Milacron · Mar 27, 2017

SAG 180 said:
If filling cracks in granite is anything like filling cracks in cement with epoxy, it will crack beside the line of epoxy not long after you fill it unless the underlying support for the granite is ultra rigid.

Which it must not be or it wouldn't have cracked in the first place !

DavidScott · Mar 27, 2017

Black super glue? I know super glue is very popular with filling small chips in stone. You can get kits of colored super glue just for this purpose. Once it cures cut it flat with a new razor blade. The way I do it is with a penetrating epoxy for stone. It follows cracks real well but the smallest kit is 3 pints.

SAG 180 · Mar 27, 2017

Milacron said:
Which it must not be or it wouldn't have cracked in the first place !

Exactly, so unless there's some way to shore up the support for the granite, the crack filler will have to be flexible.

SAG 180 · Mar 27, 2017

DavidScott said:
Black super glue? I know super glue is very popular with filling small chips in stone. You can get kits of colored super glue just for this purpose. Once it cures cut it flat with a new razor blade. The way I do it is with a penetrating epoxy for stone. It follows cracks real well but the smallest kit is 3 pints.

I patted myself on the back after filling cracks in a windscreen with superglue.....then it cured fully and shrank making the cracks visible again.

Peter from Holland · Mar 27, 2017

I would look into a waterthin product that penetrates the crack
Here we have a product to impregnate wood that is about to rot Its like water
Or perhaps even loctite
Ad some black dye perhaps

Peter

mach2 · Mar 27, 2017

Visit your local stone counter top fabricator. They have adhesive materials and the know how to do that kind of repair. They do it all the time even with new tops. A countertop fabricator may have also be able to tell you why it cracked in the first place.

DavidScott · Mar 27, 2017

The "granite" used for counter tops rarely is true granite. Photos would help here. Are the cracks natural fissures or stress cracks? Super glue is only cosmetic, Akabond 631, the penetrating epoxy I use, will glue the stone together quite well. When fabricating stone and a piece breaks off quite often the fix is to glue it back on and finish the job. The correct epoxy will fix about anything with stone. Keep in mind most "granite" slabs are soaked in epoxy before they are polished. Doing this with real granite would be useless.

Admin5 · Mar 27, 2017

mach2 said:
Visit your local stone counter top fabricator.

I doubt we have a local stone counter top fabricator. We do have a cultured marble fabricator but they are wholesale only and would probably give me the two headed look.

Milacron

adama · Mar 27, 2017

West system epoxy with graphite dust, best mixed well away from the use location though, because the stuff goes every were especially if you sneeze! Took me 2 coats of emulsion on the wall to fix that stuff up. Won't shrink, and is a smooth hygienic surface once done too!

Simply mix it up about 10% graphite to the west system. Masking tape either side of crack, fill leaving a little raised by squeegeeing in and let cure partially then remove tape and trim flush with a razor blade, then leave alone to fully harden done right it will be visible just but with a bit of use - buffing it will disappear - blend in ever better in use in no time especially if its the typical ziggy zaggy type crack granite normally gets along the crystal boundaries. If the cracks across the coarse crystals then i know of no way of making it totally disappear sorry.

Can't fill cracks in windscreens, but stone chips using the UV resin when caught early do well in my experience, yet to have one crack after filling it and the resin kits are only a couple of quid of ebay.

.

Terry Keeley · Mar 27, 2017

As (sorta) mentioned if the crack is small I would go with a good slow curing epoxy (West system with 206 hardener) and a pigment: http://www.uscomposites.com/pigments.html

I use carbon fiber filler quite a bit (called milled carbon) and it would work well if the crack is larger than about say 1/16" and you need some structural support.

Either way apply with a curved tip syringe (Monoject) and scrape the excess off before full cure with a straight razor blade.

I bet you'd have trouble telling where the crack was.

gustafson · Mar 27, 2017

The installer of my 'Silestone' counter demonstrated its toughness with a utility knife, raking the tip across it without a mark.

I mention because rather than trying to neaten up whatever you use when wet, wait for it to dry and shave with a utility knife.

I prefer urethane over silicone, Sikaflex is good stuff, you will only get it off when the skin sheds

mach2 · Mar 27, 2017

Admin5 said:
I doubt we have a local stone counter top fabricator. We do have a cultured marble fabricator but they are wholesale only and would probably give me the two headed look.

Milacron

They are all over South Carolina. Try a google search with this term:

stone countertop fabricator in South Carolina

When we did more stone design it was as simple as calling the fabricator and he would go take a look and tells what to specify. Now days most of the stone counter tops go into residential projects. Should have no problem in South Carolina. Might have to ask around a little.

Sparky961 · Mar 27, 2017

Various nice repairs can be done by pulverizing the parent material and mixing it into a clear epoxy base that's used to fill the void.

You could crack a corner off of your AA surface plate and smash it up with a hammer (don't forget your safety glasses

) or you might be able to find a small hidden place on the floating city where you can take some donor material to do the same. Failing all of that, I'm sure you can "accidentally" drop a granite floor tile at your local Home Depot and pocket the broken corner :P . Come to think of it, you could probably even find a nice dark rock on the beach that looks similar.

Dammit Jim, I'm a machinist not a geologist!

henrya · Mar 28, 2017

The suggestions to use west system epoxy are good ideas. Carbon black might be a good pigment if your granite is really black. Otherwise look around for things that seem to be about the right color.

I would not use a filler but only the pigment and you might make multiple applications to keep the epoxy from building up too much heat and bubbling. When you're done and the epoxy is built up above the flat surface slice it off with a brand-new single edge razor.

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OT- Any speciality concoction for cosmetic filling tiny cracks in black granite ?

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