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Removing Discolorations from Stone Materials

Working in fabrication, you no doubt will receive questions from people regarding discolorations on stone surfaces. Knowing about the various kinds of discolorations, what causes them, and what to do about them is only the beginning. Knowing how to treat discolorations is also important. In this "how to" article, we will look at some different kinds of discolorations that appear on stone surfaces. We will also discuss how to go about removing these discolorations when you come across them.

Kinds of Stone Discoloration

When it comes to stone materials there are a variety of material types and by the same token, there are several products for treating them as well. What are some of the different kinds of stone materials, and what are the discolorations for which they must be treated? Below is a table that summarizes not only the materials, but also the products used to treat the discolorations:

Material Discoloration Treatment(s)
Natural Stone (Marble, Granite, Onyx, etc.) Stains from Water-based Substances Poultice Powder or Poultice Pouch
Engineered Stone (a.k.a. Quartz) Limescale and Mineral Deposits Quartz Ax Cleaner
Natural Stone (Quartzite, Granite, Marble, etc.) Stains from Oil-based Substances Poultice Powder or Poultice Pouch
Acid Resistant Surfaces* Cement Residue and Limescale Cement Remover
Natural Calcareous Stone (Marble, Limestone, Onyx, etc.) Etching Etch Remover
Natural Stone (Granite, Marble, Limestone, etc.) Rust Stains TeRust Stain Remover
Quartz (a.k.a. Engineered Stone) Fingerprints, cosmetics, wax, food, etc. Bravo! Stain Fighter
Natural Stone (Granite, Marble, Quartzite, etc.) Green Stains and Bluing TeBlossom Green Stain Removal Kit
Various Surfaces Wax Wax Remover
Natural Stone (Granite, Quartzite, Marble, etc.) Ager Residue Ager Remover

As you can see, there is diversity when it comes to discolorations on natural stone and other materials. Let's look briefly at some of those discolorations and what makes the treatment(s) for each different.

Water Based and Oil Based Stains

There are several types of stains that occur on natural stone surfaces. Two of these include oil based stains and water based stains. Just like the names indicate, these are substances that have oil or water as their base. Removing these kinds of stains is accomplished by making use of a treatment called a "poultice". The word is derived Greek word for porridge.

Poultice Powder Stain Remover

Removing oil and water based stains using a poultice powder as a stain remover is a technique that draws the stain out of the stone by reversing the process. So in essence, the stain comes out of the stone virtually the same way it got into the stone. This technique is effective for removing stains that are water or oil based.

Poultice Demonstration

Stain Removing Poultice Pouches

Similar to the poultice powder method is the poultice pouch method. This is the exact same concept as using the powder. It works on the same types of stains (oil and water based). The difference is that the poultice powder is enclosed in a fibrous pouch. So the treatment process is not quite as much of a mess since the powder is contained and not lying directly on the stone.

So for oil and water based stains on natural stone surfaces, using the poultice technique is effective. However, there are other discolorations specific to certain kinds of stone.

Etching of Calcareous Stone

Another type of discoloration that is often mistaken for a stain is etching. This discoloration is unique to a very specific family of stone referred to as "calcareous stone". Caclareous stone is called such because of its containing calcium carbonate, or calcite. There are a few specific stones in this group. Some of them include:

  • Limestone
  • Marble
  • Onyx
  • Travertine

Each of those natural stone materials contain calcium carbonate and is susceptible to etching.

How Calcareous Stone Becomes Etched

As mentioned above, etching is not a "stain" per se. Rather, it is a discoloration that results from a reaction that the stone has to acidic substances. Calcium carbonate (the main substance in calcareous stones) reacts with acid. When this happens, the calcium carbonate is dissolved. On surfaces that have been polished, the result is a dull spot. On honed materials, the etch appears as a dark spot on the stone. In both cases though, the same thing has happened. Part of the stone has been dissolved and a contrast in the appearance is easily seen.

Etch Remover

So if an etch is caused by part of the stone being removed, then how do you correct it? The key lies not in undoing what occurred, but making the contrast in the stone's appearance go away. How do you do that? By using an etch remover. Etch removers work by gently "evening out" the discoloration and blending the edges of the affected area so that the discoloration is not easily seen, if visible at all.

Etch Remover Demonstration

Mineral Deposits On Quartz

Like the discoloration we just looked at on calcareous stone, mineral deposits on quartz, or engineered stone, are not really "stains". Rather, they are a result of mineral build up on the surface of the material. You could think of it as the opposite of etching. Instead of minerals being removed from the stone, minerals become attached to the surface.

How to Treat Mineral Deposits

Since quartz is non-porous, there is no need to treat the stain in the pores of this engineered material. Instead, the answer is to use a product that will remove the mineral deposits from the surface. Using a product designed to remove limescale from quartz surfaces is the solution.

As we have seen in this article, there are a number of discolorations that affect natural and engineered stone materials. Knowing which kind of material you are working with and what type of stone you are treating will greatly help you to remedy the situation in the best way possible.

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