Removing Stains from Marble and other Natural Stones
Little Billy decided he was 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 this 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.
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. Ammonium 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 Hypochlorite
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
Re-hone
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
Grind/re-hone/polish
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.