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Poulticing Powers:

Clays (attapulgie, Kaolin, Fullers Earth)
Chalk (whiting)
Sepiolite (hydrous magnesium silicate) magnesium Tinsilicafe
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 poultice to dilute and /or react with the stain. The process is rather simple. 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 power/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 in the stain removal chart for the proper chemical to apply. If the stain is unknown, then you need to play detective. Try to determine 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 form the coffee pot 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 through 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.

I have found that most stains can be classified into the following categories:

1.Oil Based Stains - Grease, tar, cooking oil and food stains

2.Organic Stains - Coffee, tea, fruit, tobacco, cosmetics, ect.

3. Metal Stains - Iron (rust), copper, bronze, ect

4. Biological Stains- Algae, mildew, lichens, ect.

5. Ink Stains - Magic marker, pen, ink, ect.

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:

1. Wet the stained area with distilled water. Pre-wetting fills the pores of the stone with water-isolation the stain and accelerating the removal by the chemical.

2. Prepare the poultice. If a power is to be used, pre-mix the power and the chemical of choice into a thick paste of the consistency of peanut butter. In other words. wet it enough so that it does not run.
If a paper poultice is to be used-soak the paper in the chemical. Lift the paper out of the chemical until it stops dripping.

3. Apply the poultice to the stain-being careful not to spill any on the nonstained areas. Apply approximately one-quarter-inch thick overlapping the stain area by about one inch.

4. Cover the poultice with plastic (food wrap works great). Tape the plastic down to seal the edges.

5. 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.

6. Remove the poultice from the stain. Rinse the distilled water and buff dry with a soft cloth. If the stain is not removed, apply the poultice again. It may take up to 5 applications for difficult stains.

7. Some chemicals may etch the marble surface. If this occurs, then apply polishing power and buff with a piece of burlap to restore the shine.

Summary steps to remove stains:

1. Identify the stain if possible.
2. Prevent reoccurrence. Locate the source of the staining, and if possible, prevent it from occurring again.
3. Lightly scrub the stained area with a mild cleaner.
4. Patch test if necessary.
5. Apply a poultice to the stain, as per instructions.

Removing Stains from Marble and other Natural Stones

Little Billy - decided he is an artist - used a black magic marker to create an artistic masterpiece on the new white marble floor.

The workman - repairing the roof - tramples tar all over your building's expensive granite lobby floor.

Your maid wants to deeply clean your shower and applies an acidic cleaner to the marble leaving deep white marks reminiscent of the Mississippi river basin.

These are just a few of the countless variety of actions which can result in the staining of marble. granite. and other stone surfaces. Is the stone ruined? 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 the article and a few simple techniques are what I consider to be the magic potion.

Marble 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.

Some of the more common poulticing materials and powders are:

Stain Removal Guide

All solutions are given starting with the gentlest method first. All the chemical solutions mentioned can be purchased at most hardware stores or from a marble supply distributor.

1. Iron Stains (rust)

Poultice with on the the following:
a. Sodium citrate and glycerin or
b. Ammononium Oxalate or
c. Oxalic Acid or
d. Orthophosphoric Acid and Sodium Salt of EDTA in water or
e. Dilute Hydrofluoric Acid or
f. cannot be removed, is part of the stone

2. Ink

Poultice with one of the following:
a. Light colored marbles only use Bleach or Hydrogen Peroxide;
b. Dark marbles use Lacquer Thinner or Acetone;
c. Methyl Chloride

3. Oil Based Stains (grease, cooking oil, tar, food stains, etc.)

Clean with:
a. Scouring Power with Bleach or
b. Household Detergent or
c. Ammonia or
d. Mineral spirits or
poultice with:
e. Baking Soda or
f. Mineral Spirits or
g. Methyl chloride

4. Organic Stains (paper, tea, coffee, cosmetics, fruit, tobacco, etc.)

a. Pour Hydrogen Peroxide 35% directly on stain and add a few drops of ammonia, leave until bubbling stop ors
b. Repeat above but add poultice or
c. Acetone or Toluene or Xylene

5. Efflorescence

Poultice with:
a. Distilled Water

6. Copper Stains

Poultice with:
a. Ammonium Chloride or
b. Ammonium Hydroxide

7. Biological Stains (Lichens, algae, moss, fungi, mildew, etc.)

Clean with:
a. Dilute Ammonia or
b. Bleach or
c. Hydrogen Peroxide or
d. Sodium Hypochiorite

8. Wax (Acrylic yellowing coatings)

Strip with:
Alkaline Stripper

9. Urethane Coatings

a. Methyl Chloride or
b. Grinding

10. Crystallization coatings

a. Strip with Oxalic Acid based Stripper or
b. Methyl Chloride

11. Paint

a. Alkaline Paint Remover
b. Methyl Chloride

12. Grout and Thin Set Residue

a. Scrub with neutral cleaner and red pad or
b. Re-polish

13. Scratches

a. Re-polish or
b. Re-hone

14. Streaking

a. Buff with felt pad-dry or
b. 0000 Steel wool-dry or
c. Re-polish

15. Acid/Alkaline Etching

a. Re-polish or
b. Re-hone

16. Stuns/Crystal Fractures


17.Water Spots and Rings

a. Buff with a dry 0000 Steel wool or
b. Re-polish or
c. Re-hone

18. Discoloration

Clean with:
a. Alkaline Stripper or
Poultice with:
b. Bleach or
c. Hydrogen Peroxide or
d. Re-hone and polish

19. Swirl Marks from steel wool

a. Re-polish or
b. Re-hone

20. Random Dull Spots

a. Check for etching or
b. Re-polish

21.Excess Lippage


22. Warped Tiles

Remove and Replace

23. Loose Tiles

Remove and Reset

If the problem is serious in nature or too large in size. consider using the services
of a qualified stone restoration expert in your area.

Frediric M. Hueston has a degree in Chemistry and is also an experienced and accomplished marble and stone craftsman, Founder and president of Cambridge Floor Care Systems, based in Winter Park, Florida. Hueston is a recognized leader in the marble and stone care and restoration field.

Hueston is a member of Building Stone Institute's Marble (and stone) Care and Maintenance Committee.

Greg Kazanjian
ASLAN Stoneworks

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