Polyurethane on Marble
(Cabo San Lucas, MX)
Outdoor natural stone marble top for table in Mexico. Very dull and I would like a shine. Can I use interior/exterior Polyurethane?
I don't have much experience with polyurethane on marble, as we always put a shine on marble by honing and polishing.
I never recommend any coating on marble as once the coating begins to deteriorate, is starts to peel.
This can happen as soon as a few weeks and once it happens, you have a very unsightly piece of marble.
In your case this is outdoors, so I suspect the polyurethane will begin to breakdown rather quickly if it's exposed to he sun.
Even if you honed and polished the marble table the sun will breakdown the shine.
The difference with honing and polishing, the shine will only fade and not peel and look terrible.
Also, if you use a coating like a polyurethane, when it comes time to re-coat, you will need to strip the old coating off and this will require the use of very aggressive chemicals.
So in my opinion, I would not use polyurethane on your marble top.
The shine most likely will not last and and when it begins to break down, it will look very bad.
I hope this helps.