Stain Removal Basics
By Frederick M. Hueston, Technical Editor

"Help, I spilled cooking oil all over my new granite countertop and it left a huge stain." How do I remove
the yellow stains from my white marble shower?" Can the stains on my floor be removed or do I need to
replace the floor?"
These are just a few of the countless questions fabricators, restoration contractors and others in the
industry get on a daily basis. Is the stone mined? Does it need to be replaced? The answer may be "yes"-
unless you have the magic potion that will remove most imbedded stains from stone.
The "Guide to Stain Removal" which appears as part of this article and a few simple techniques are what I
consider to be the magic potion.
Marble, granite and natural stone are porous materials. This porosity is why it stains so easily. It is also
why stains can be removed. All that's needed to remove a stain is to reverse the staining process. In other
words, the stone has literally absorbed the stain and we simply re-absorb it into a different material. This
different material is what we call a poultice. A poultice can be made with powdered whiting and hydrogen
peroxide or a chemical reducing agent-depending on the nature of the stain. Whiting is sold in most paint
stores. The poultice should be made and applied as described for removal of each particular stain.
Poultices are commonly powder or cloth materials that can be mixed with a chemical and placed on top of the stain. Refer to the table below for some of the more common poultice materials. Clays and diatomaceous earth are safe and readily available, but do not use whiting or clays containing iron with an acidic chemical; iron will react with the
acid, and may cause rust staining. It is best to purchase powders that are designed specifically for stone and tile. Consult a stone restoration specialist or your stone supplier if in doubt.

Poultice materials:
Paper towels
Cotton balls
Gauze pads
Clays such as Attapulgite, Kaolin, Fuller's Earth
Talc Chalk (whiting)
Sepiolite (hydrous magnesium silicate)
Diatomaceous earth
Methyl cellulose
Flour
Saw dust
I have found that most stains can 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, etc.
Metal Stains: Iron (rust), copper, bronze, etc.
Biological Stains: Algae, mildew, lichens, etc.
Ink Stains: Magic marker, pen, ink, etc.
There are, of course, other materials that will cause staining. but these five categories are the most
common.
Applying The Poultice
Once the stain is identified, the following steps can be followed:
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 a powder is to be used, pre mix the powder and the chemical of choice into a
thick paste, the consistency of peanut butter. In other words, wet it enough so that it does not run. If a
paper politice is to be used, soak the paper in the chemical. Lift the paper out of the chemical until it stops
dripping.
Apply the poultice to the stain being careful not to spill any on the non stained areas. Apply approximately
1/4-inch thick over-lapping the stain area by about one inch.
Cover the poultice with plastic (food wrap works great). Tape the plastic down to seal the edges. It
also helps to poke several small holes in the plastic. so that the powder will dry out. Failure to do this may
result in the poltice staying wet.
Allow the poultice to dry thoroughly. This is a very important step. The drying of the poultice is what
pulls the stain from the stone into the poultice material. If the poultice is not allowed to dry, the stain may
not be removed. Drying usually takes 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 up to five applications for difficult stains.
Some chemicals may etch marble and limestone surfaces. If this occurs, then apply polishing powder and
buff with a piece of burlap to restore the shine.
Poulticing Powders:
Clays (Attapulgite, Kaolin, Fullers earth)
Talc
Chalk (whiting)
Sepiolite (hydrous magnesium silicate)
Diatomaceous Earth
Methyl Cellulose
Clays and diatomaceous earth are usually the best. Do not use whiting or iron-type clays, such as Fullers
Earth, with acidic chemicals. They will react with the material, canceling the effect of the poultice.
Many stains are so deeply imbedded that the poultice alone will not be completely effective. Some type of
chemical solution will need to be added to the poulice. When the poultice and chemical are applied, the
chemical is absorbed into the stone. The chemical reacts with the stain and is re-absorbed into the
powder/material. 
Stain Removing Chemicals:
How do you choose the proper chemical for a given stain?
First, you need to identify the stain. This is the most important step in stain removal. If you know what
caused the stain, you can easily look at a stain removal chart for the proper chemical to apply. If the stain is
unknown, then you need to play detective. Try what caused the stain. If the stain is near a plant container,
it might be that the plant was over watered and the soil has leached iron onto the stone. The color of the
stain may help to identify the cause. Brownish color stains may be iron (rust) stains. The shape or the
pattern of the stain may be helpful. Small droplet size spots leading from the coffeepot to someone's desk
are a sure giveaway. Do some investigating and use your powers of observation. This will almost always
lead to the identification of the cause of the stain.
If, after thorough investigation, you still have no idea what the stain is, then you will need to perform a
patch test. A patch test simply means applying several chemical poultices to determine which will remove
the stain. There are also pre-prepared poltice mixes that have the chemicals already added. All you have to do is add water. One way to reduce the amount of staining on any stone surface is to make sure it is sealed with a good penetrating sealer or impregnator
Stain Removal Guide:
Iron (rust) - Poultice with Oxalic Acid + Powder + Water. May also try a product called Iron-Out
(available at hardware stores). Both mixtures may etch polished marble, so re polishing will be necessary.
Ink - Poultice with Mineral Spirits or Methylene Chloride +Powder.
Oil - Poultice with Ammonia+ Powder Methylene Chloride can also be used on tough oil stains.
Coffee, Tea & Food - Poultice with 20 percent Hydrogen Peroxide + Powder.
Copper - Poultice with Ammonium Chloride + Powder
Paint (water-based) - poultice with a commercial paint remover + Powder
Paint (oil) Poultice with Mineral Spirits + Powder. Deep stains may require Methylene Chloride.
Please use extra caution when handling all chemicals listed above. Thoroughly read Material Safety Data
Sheets for each chemical before use.

Originally published in August 12, 2001 issue of STONE magazine. This article appears by permission of the author.