Thread: Polycrylic sealant???

I have a CNAT that is developing some small cracks in the ends. I am afraid that it will split one day if I do not seal the stone. I also have a couple of other natural stones that might benefit from sealant as well.

I know that the traditional sealant for natural stones is Urushi, but it is difficult to obtain and may cost as much as the CNAT I am trying to protect.

I know people have used fingernail polish, but I would prefer to avoid the acetone fumes.

I wondered if anyone has tried using Minwax Polycrylic which is a water-based combination of polyurethane and acrylic. I have used it successfully as a wood finish, but do not know how it would work on stone.

I have used ordinary shellac to seal Jnats and nagura with very good results. Alcohol is the volatile solvent, and the fumes are mild and dissipate quickly.

Originally Posted by RayClem

I have a CNAT that is developing some small cracks in the ends. I am afraid that it will split one day if I do not seal the stone. I also have a couple of other natural stones that might benefit from sealant as well.

I know that the traditional sealant for natural stones is Urushi, but it is difficult to obtain and may cost as much as the CNAT I am trying to protect.

I know people have used fingernail polish, but I would prefer to avoid the acetone fumes.

I wondered if anyone has tried using Minwax Polycrylic which is a water-based combination of polyurethane and acrylic. I have used it successfully as a wood finish, but do not know how it would work on stone.

Urushi might sound "natural", "environmentally safe", "organic" and all that green popular stuff but it's actually way more dangerous than acetone or anything else you can use as a sealant, if it comes in contact with your skin or even vapors from it! Urushiol, it's worse than poison ivy, I've learned that the hard way.
For your choice of wood finish, it says "it cleans easily with warm water", so, even dry, I wouldn't trust it for stone that can't work unless they are wet. Anything water-based would probably not do a good job.
The by far easiest way is to get a transparent acrylic varnish spray; it smells the first couple of minutes, it's dry in half an hour, and a couple of hours later you can leave your stone on any surface of the house without worrying that it will get glued on it. Nail polish works as well but it's less cost effective. If the stone was some thousand dollar stamped one of a kind piece, you might want to consider urushi but for anything else, all you need is a ventilated room or even better, the outside to apply, and in less than 5' the smell will be almost gone, and the varnish stays for years, a can of acrylic spray lasts for many stones and many hands.
Shellac is a good idea as well, but again, it takes some time to prepare if you do it yourself and apply. You will probably pay more for it too.

Originally Posted by Vasilis

Urushi might sound "natural", "environmentally safe", "organic" and all that green popular stuff but it's actually way more dangerous than acetone or anything else you can use as a sealant, if it comes in contact with your skin or even vapors from it! Urushiol, it's worse than poison ivy, I've learned that the hard way.
For your choice of wood finish, it says "it cleans easily with warm water", so, even dry, I wouldn't trust it for stone that can't work unless they are wet. Anything water-based would probably not do a good job.
The by far easiest way is to get a transparent acrylic varnish spray; it smells the first couple of minutes, it's dry in half an hour, and a couple of hours later you can leave your stone on any surface of the house without worrying that it will get glued on it. Nail polish works as well but it's less cost effective. If the stone was some thousand dollar stamped one of a kind piece, you might want to consider urushi but for anything else, all you need is a ventilated room or even better, the outside to apply, and in less than 5' the smell will be almost gone, and the varnish stays for years, a can of acrylic spray lasts for many stones and many hands.
Shellac is a good idea as well, but again, it takes some time to prepare if you do it yourself and apply. You will probably pay more for it too.

Polycrylic is water based and it does clean up easily with water. However, after several days of curing it becomes a plastic. The plastic is largely acrylic, like the acrylic that is used in nail polish. It is water resistant, not waterproof, so I would not recommend it for stones you plan to soak for long periods. However, many naturals stones are so dense that little water absorbs into the stone. The water stays mostly on the surface acting as a lubricant.

By the way, shellac is also not waterproof. It is not recommended for water exposure to water exceeding four hours.


I had a can of Polycrylic in the basement, so I decided to try it on my CNAT. I figured that the worst thing that could happen is that the sealant would not work and the stone would split and I would be out $45.

I applied four thin coats to the stone, allowing at least two hours between coats.
I did this on a layer of wax paper to prevent the coating from seeping onto the face of the stone I use for honing, but I got some around the edges of the face anyway. When I used water to remove the excess, the coating on the sealed portion of the stone started to turn milky white indicating it was rehydrating. However, the coating had only hours of curing, not days. After a few more hours of drying time, the milkiness went away.

After the coating had cured 24 hours, I lapped the stone under running water to be sure I had removed all traces of sealant from the face. This time, there was no milkiness. I will let the coating cure a few more days before using the stone. By then I should be fine.

Again, I would not recommend this sealant for a stone that needs to be soaked for more than a few minutes, but for stones that are essentially splash and go, it seems to be suitable.

Some water based finishes, do not hold up to water submersion or protracted water exposure.

Just paint a garden rock, with the finish you want to test, let it dry, per instructions, some take days to fully cure. Multiple coats are better than a single heavy coat.

Then drop it in water, if it turns milky, it not water proof. Any stone that requires soaking probably should not be sealed.

I've been having terrific results with this stuff. I do not soak my stones and I do clean and dry them afterwards. Been using it for about three months now with all my newly acquired unprotected jnats. I apply with a cut sponge brush. Per directions.

Thanks for that. I was starting to wonder what I should use to seal the Jnat I have on the way if it's not already been done. If a basic Polyurethane will do it I've got some good quality stuff lying about I can press into service.