Discolored Cultured Marble

Old 07-07-07, 02:51 PM
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Discolored Cultured Marble

I have yellow discoloration on my white cultured marble under two sources, 1) navy blue plastic tissue cover and soap dish and 2) wicker baskets holding towels. (in 2 bathrooms)

The soap dish just has a dry bar of rarely used soap sitting in it, so it appears to be the dish itself. These products are all widely available at many home decor stores and I've never seen any product that comes with a warning not to be placed on a cultured marble surface.

Q1) Any ideas of what the plastic pieces and the wicker could have in common to cause the same discoloration? Obviously I will stop using these pieces, but until I know what is causing the problem, I don't know what to replace them with.

Q2) Any ideas on how to get rid of the discoloration?

Q3) For our next home, what is a recommended countertop surface that isn't as sensative as cultured marble appears to be? This is all this builder offered. Our last home had tan cultured marble and I never had this problem, but maybe I just didn't see it because of the color.

Any ideas appreciated!

Old 08-09-07, 05:32 PM
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yellow discoloration on cultured marble

dubbelyu, I don't have any answers for you -- just want to say the same thing happened to us. We have a new cultured marble bathroom countertop, white on white color, 5 months old, and when I cleaned the counter the other day, found yellow discoloration under the soap dispenser and soap dish. I've been cleaning the bathroom frequently since installation and this is the first time I noticed this.

I haven't been able to find any information on what might have caused this. The installer came today and buffed out the stain, but we are frustrated trying to figure out why this happened.

I have cultured marble in another house more than 15 years old, all similar color, and no stains. It's held up beautifully, which is why we installed it in the new bathroom. We're now trying to figure out if we should stick with the same vendor for yet another counter top. Was it a fluke or bad recipe?

Old 08-09-07, 06:12 PM
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Not all cultured marble products are created equal. Higher quality cultured marbled tops have thicker and better gel coating. Thus, some are less impervious to stains, more durable, and allow for buffing out scratches. Products that contain dyes, PVC, and other substances can cause discoloration.

It is important not to use abrasive products when cleaning cultured marble. Hydrogen peroxide, a mild oxygenating bleach, left to pool on stains may lift them. The strongest oxygenating bleach is clorine bleach (Clorox) and may be able to lift discoloration. These bleaches may be able to lift dye transfer stains. PVC and other chemical migrations tend to cause permanent discoloration.

Attempts to use mild abrasives include baking soda, toothpaste, Soft Scrub, BarKeepers Friend, Zud, or other mild abrasive. The key is not to use an abrasive.

For best results with cultured marble tops is to keep them sealed with Gel Gloss, auto wax, or other product containing wax. It is also important not to place anything on gel coat that could potentially cause discoloration, stains, or scratches.
Old 02-18-13, 07:20 AM
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box yellowing

The problem you're experiencing is known in this industry as "black box yellowing" or just "box yellowing". This may seem counter-intuitive, but the discoloring is actually caused by the areas NOT getting exposure to light. The two items you cite have nothing in common other than that they block light from getting to the vanity top.

There is no fix. What has discolored is the gel-coat and it has discolored throughout it's entire thickness of between 15-30 mils. In order to remove the discoloration therefore, you would have to remove the gel-coat and that would expose the substrate matrix which is porous. Bottom line, you're stuck with it.

Another poster mentioned that not all gel-coats are created equal. That's true. Buying a cultured marble top at a big box store MAY not get you the best quality product. My advice is to purchase these products directly from the manufacturer, you can find them almost anywhere. Better, more expensive gel-coats are less likely to yellow due to improved chemistry.
Old 02-18-13, 07:31 AM
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Welcome to the forums. You've responded to a five and half year old question, the person who asked the question has not been on the forums since a couple days after they posted the question.

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