Natural Stones

 

Stain Removal Guide

 

Natural stone is porous by nature and will stain.  Because of this, the stain may sometimes be removed by reversing the staining process.  If you re-absorb the stain into a medium, it can be removed from the stone.  The typical medium is called a poultice.

Stains should be treated as soon as possible.  As time goes by the stain will set and it becomes increasingly difficult to remove it.  Attempts to remove stains should not proceed stain determination since using the proper removal technique is important to achieve the desired results. 

Test patches should be performed to identify the type of stain and the recommend procedure for removal.

The poultice may be a material (cotton balls, paper towels, etc.) or a powder (Poultice Plus, clays, or diatomaceous earth), which is usually preferred.  Mix the powder with distilled water to make a paste-like substance.  Mix this paste with the chemical from the chart below.  Mix the resulting paste to a consistency similar to peanut butter.  This paste can then be applied to the stain to a thickness of ¹/₈ to ¹/₄ of an inch, overlapping the edges of the stain by 1 or 2 inches.  Cover the area with plastic wrap and secure the edges sealed tight with non-marking tape.  The poultice must dry completely (24 to 48 hours) and as it dries, it will pull the stain out of the stone into the paste.  If the stain has lessened but not removed completely, reapply as often as required.

Please note that some chemicals that are necessary for stain removal will remove the finish of polished or lightly honed limestones.  As a result, re-polishing with abrasives may be necessary.

Typical stains include organic (coffee, tea, tobacco), Inorganic (rust, metal), Biological (mildew, mold, fungus, algae), Oil based (grease, cooking oil, food stains) and Ink (ball point pen, felt pen).

 

Removal Chart

All solutions below are given starting with the gentlest method first.  Always test a small area to ensure the desired effect is achieved.

Organic                  

    clean with:                  1.   Liquid Poultice

                                         2.   35% Hydrogen Peroxide poured directly on the stain and add a few drops of ammonia.  Leave until bubbling stops.

Iron                         

    poultice with:               1.   Liquid Poultice

                                       2.    Ammonium Oxalate

                                        3.   Oxalic Acid

Copper                   

    poultice with:                1.   Ammonia Chloride

                                       2.   Ammonia Hydroxide

    biological clean with:   1.   Liquid Poultice

                                                   2.    Diluted Ammonia

                                       3.    Bleach

Oil Based           

   clean with:                    1.    Miraclean  #1

                                       2.    Liquid Poultice

                                                   3.    Mira Strip

                                       4.         Bleach

                                       5.         Household detergent

                                       6.         Ammonia

                                       7.         Mineral Spirits

    poultice with:                1.    Mineral Spirits

                                       2.        Methyl Chloride

Crystallization         

    Re-hone the surface with abrasives.

 

Grout & Thin-set     

    Clean with Grout and Concrete Film Remover diluted 5:1 on honed or sawcut surfaces and 2:1 on flamed granite.  Do not use on polished surfaces.