Oxalic acids when used correctly have the potential to polish a marble surface. However, before you start polishing you have to have some understanding of what is happening on the surface. Marble etches when attacking chemicals dissolve the weaker calcite minerals on marble. The small depressions left behind refract light differently when compared to a smooth surface. When applying strong acids, the higher points dissolve leaving a flatter surface to properly reflect light, hence removing the etch mark. Unfortunately, working with polishing acids takes practice. ItâÂÂs not as simple as pouring some powder on the surface sprinkling some water on it and rubbing away with a 3m pad. Well, actually it is⦠you just need to master the art of feathering. I will prefix this next sentence with; oxalic acid is also great for honing marble, meaning itâÂÂs equally as good at taking the shine off. If you donâÂÂt know how to feather, you will continually chase your tail. Feathering allows you to restore the area of concern and blend it into the areas that are not affected. What usually happens is you get the affected area shining but when you step away a few feet you can see exactly where you were working. Most of the time this looks worse than the smaller etch you were trying to repair. One trick of the trade is to use less chemical and more mechanical; smaller concentrations of chemical and more elbow grease most always yields better results.
The truth is its been about 10 years or so since I have had to buy polishing acids but when I was still active in the restoration industry there were other products on the market that were both better for the stone and better for your lungs, trust me acids are not user friendly. I found the best product for polishing marble was called 5X from Italian craftsman. It was a blend of 5 different chemicals that created a mix that was not as aggressive.
Dan