Marble and natural stone are porous materials. The most successful way to remove staining is to endeavour to reverse the original staining process. The easiest method for attempting this is to try to absorb the staining material into another material which is referred to as a ‘poultice’. A poultice can be made from many varied products but is most often a powdered whiting and hydrogen peroxide mix or a chemical reducing agent - depending on the nature of the stain.

Some of the more common poulticing materials and powders are:

Clays and diatomaceous earth are usually the best. Do not use whiting or iron type clays such as Fullers Earth with acidic chemicals. A chemical reaction will occur, canceling the effect of the poultice. Many stains are so deeply imbedded that the poultice alone will not be completely effective. A chemical solution will need to be added to the poultice to dilute and/or react with the stain. When the poultice and chemical is absorbed into the stone, the chemical reacts with the stain and is re-absorbed into the poultice powder material.
 

Stain-Removing Chemicals

To select the correct chemical, firstly, you will need to identify the stain type. Once it is known you should refer to the below stain removal guide for the appropriate chemical to apply. If the origin of the stain is unknown, you will need to begin some sample testing. The color of the stain may help to identify the cause. (i.e Dark brown stains may have been caused by iron (rust) stains). The shape or pattern of the stain may also be helpful. If, after thorough investigation you are unable to identify the stain origin, you will need to perform some on site patch tests.

Most common stains may be classified into one of the following categories:

-OIL BASED STAINS - Grease, tar, cooking oil and food stains
-ORGANIC STAINS - Coffee, tea fruit, tobacco, cosmetics, bark or leaf litter
-METAL STAINS - Iron (rust) copper, bronze etc.
-BIOLOGICAL STAINS - Algae, mildew, etc
-INK STAINS- Magic marker, pen, ink etc.
 

Applying the Poultice

Once the stain is identified, please follow the steps shown below:

-Wet the stained area with distilled water. Pre-wetting fills the pores of the stone with water - isolating the stain and accelerating the removal by the chemical.
-Prepare the poultice. If powder is to be used, pre-mix the powder and the chemical of choice into a thick paste.

If a paper poultice is to be used - soak the paper in the chemical. Lift the paper out of the chemical and allow it to drain until it stops dripping.

-Apply the poultice to the stain - being careful not to spill any on the non stained areas. Apply approximately 3mm thick overlapping the stain area by about 10mm all round.
-Cover the poultice with a plastic film. Tape the plastic down to seal the edges.

Allow the poultice to dry thoroughly. The drying of the poultice is what draws the stain from the stone into the poultice material. If the poultice is not allowed to dry, the stain may not be removed effectively. Drying should normally take from 24 to 48 hours.

Remove the poultice from the stain. Rinse with distilled water and buff dry with a soft cloth. If the stain is not removed, apply the poultice again. It may take several applications for difficult stains.

Be aware that some chemicals may etch marble surfaces. If this occurs, apply polishing powder and buff with a piece of burlap to restore the shine.
 

Stain removal solutions

All suggestions listed below are in order, with the gentlest remedy listed first and the most severe last.

NOTE: If the problem is serious in nature or too large in size, please consult a professional cleaning contractor.