Removing Iodine Stains From Marble

CSI Division
Division 4- Masonry
Section
Marble
Last Modified

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Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.

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We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.

THE CLEANING OR REMOVAL OF STAINS FROM STONE MAY INVOLVE THE USE OF LIQUIDS, DETERGENTS OR SOLVENTS WHICH MAY RUN OFF ON ADJACENT MATERIAL, DISCOLOR THE STONE SURFACE OR SEND STAINS DEEPER INTO POROUS STONES. USE THE PRODUCTS AND TECHNIQUES DESCRIBED HERE ONLY FOR THE COMBINATIONS OF DIRT/STAIN AND STONE SPECIFIED.

PART I—GENERAL

1.01 SUMMARY

  1. This procedure includes guidance on removing iodine stains from marble with an alcohol poultice.
  2. See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
    1. Safety Precautions
    2. Historic Structures Precautions
    3. Submittals
    4. Quality Assurance
    5. Delivery, Storage and Handling
    6. Project/Site Conditions
    7. Sequencing and Scheduling

    8. General Protection (Surface and Surrounding)

      These guidelines should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from the Regional Historic Preservation Officer (RHPO).

  3. For additional information on poulticing, see 04455-02-R.
  4. For general information on the characteristics, uses and problems associated with marble, see 04455-01-S.

PART 2—PRODUCTS

2.01 MATERIALS

NOTE: When the common name of a chemical is used on the label, it is usually a sign that the substance is not as pure as the same chemical sold under its chemical name. However, the grade or purity of the common-name substance is almost certain to be adequate for stain removal work, and because it is likely to be less expensive, the common-name product should be purchased when available. Common names are indicated by an asterisk (*).

  1. Denatured Alcohol:
    1. Other chemical or common names include Methylated spirit*.
    2. Potential hazards: TOXIC AND FLAMMABLE.
    3. Available from hardware store, paint store or printer’s supply distributor.
    4. Denatured alcohol, which carries no liquor tax, should be a satisfactory substitute for ethyl alcohol for stain removing purposes.
  2. White absorbent material (molding plaster, powdered white flour, white talcum, paper towels, powdered chalk, talc, fullers earth or laundry whiting)
  3. Mineral water
  4. Plastic sheeting
  5. Clean dry towels for blotting the area after treatment

2.02 EQUIPMENT

  1. Glass or ceramic container for mixing the solution
  2. Wooden utensil for stirring the ingredients
  3. Wood or plastic spatula
  4. Masking tape

PART 3—EXECUTION

3.01 EXAMINATION

  1. Examine the marble surface CAREFULLY to determine cause of staining before proceeding with any cleaning operation.

3.02 ERECTION, INSTALLATION, APPLICATION

  1. Iodine stains will normally disappear without treatment.
  2. For quick removal, apply a poultice of denatured alcohol and whiting.
    1. Thoroughly rinse the area to be treated with mineral water.
    2. Pour the denatured alcohol in a glass or ceramic bowl. Use an amount adequate to fully cover the affected area.
    3. Thoroughly moisten the stained surface with this liquid. Be sure to dampen well beyond the stain.
    4. Mix the remaining liquid with the white absorbent material to form a paste the consistency of oatmeal or cake icing. (Approximately one pound of paste is needed for every square foot of surface area to be treated.)
    5. Using a wooden or plastic spatula, apply the paste to the stained surface in layers no more than 1/4 inch thick. The poultice should extend well beyond the stain to prevent forcing the stain into previously unstained areas.
    6. Check the coating for air pockets or voids.
    7. Cover the poultice with plastic sheeting and seal with masking tape.
    8. Let set for 48 hours (unless otherwise specified).
    9. After set period, dampen the poultice with mineral water.
    10. Remove the poultice with a wooden or plastic spatula to avoid scratching the surface.
    11. Again, rinse the cleaned area with mineral water, blot with clean towels and allow the surface to dry.
    12. Once the surface has dried completely, check for remaining residue and repeat the treatment if necessary.
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Last updated: Jul 2, 2025
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