New Marble Floor Tile Turns Green

by Paul Sinclair
(Manchester, England)

QUESTION:

In summer 2008 we had a new house built in Cyprus with high quality marble floor tiles throughout. The colour was mainly pale shades of beige/yellow with brown and red lines and colouration. The appearance after the floors were laid was high gloss. Cleaning was with pure cold water only.

After about two months some of the floor tiles (perhaps 20%) started to show a strong green colouration on the surface. This could not be removed with cleaning compounds. Removing one tile showed that the green was in the top 1mm of the tile and not throughout the depth of the tile.

The builder used a contractor to grind the top 1mm off all the floor tiles - the grinding operation was a wet grind with a second machine removing the water slurry. It took seven days to do all the floors in the house. Finally all the floors looked perfect.

Unfortunately, after a further two months the same green colour had returned to those same tiles.

Does anyone know why this might happen, what is the cause? It is not all the tiles that are affected and only the original ones that have gone green a second time. Any advice would be appreciated. Regards, Paul Sinclair

ANSWER:

Paul, I can feel your frustration. A very puzzling problem for sure.

First, you must rule out that there isn't any source of moisture underneath the marble tiles. If the sub-floor was not sealed then you could have moisture wicking up through to the marble.

Now I know you stated that the "green" is only on the top 1mm, so it would seem that it is not a moisture problem from beneath the tiles or you'd likely see evidence through the entire thickness of the tile (I agree and think this is probably not the cause).... but you need to rule it out.

My best guess is that your marble contains copper ("brown and red lines of coloration") that is being oxidized and turning green as copper does when exposed to air and moisture.


Obviously, since it's a natural product some tiles will contain more copper than others, which would explain why it's occurring only on certain tiles and the same tiles after re-surfacing.

The same type of problem can occur with white marble, which often contains iron. When exposed to moisture the iron rusts, leaches through the marble and causes brown/yellow/orange stains.

With white carrara/iron the problem usually occurs when water is behind or underneath the tile and leaches through to the surface.

Given the extent of the problem, I'd say your only good solution is total replacement. Or learn to like it.

It may have been possbile after re-surfacing to apply a topical coating or wax (not the standard impregnating sealer that is most often used on stone). A topial sealer/wax would keep air off the stone so the copper wouldn't oxidize, but topical sealers require a lot of ongoing maintenance. They scuff and scratch and get dull. Also not good to suffocate the stone.

I know green wasn't a color you had picked out, but honeslty it doesn't look too bad in the picture. It looks natural to the stone with a similar tone in color and not really like a stain or blemish.

I understand that it may look horrible in person, but I can't say the installer is to blame here, so if you don't want to pay for the job a second time then with lemons... make lemonade.

Regards,
Ryan

P.S. Get all the facts, answers, explanations and simple solutions with step-by-step instructions for any problem or question with our Granite & Marble Maintenance Manuals.

I highly recommend MB Stone Care Products to maintain all your marble, stone and granite countertops and floors in optimal condition. I've used other good products (Stone Tech, Miracle) but found MB Stone Care is the most reliable and effective.