Technical Procedures Disclaimer
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.
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 OR DRIVE THE STAINS DEEPER INTO POROUS STONES. USE THE PRODUCTS AND TECHNIQUES DESCRIBED HERE ONLY FOR THE COMBINATIONS OF DIRT/STAIN AND STONE SPECIFIED.
- This procedure includes guidance on poulticing marble stained with paints which have a linseed oil binder and "carbonaceous" or sooty soiling.
- Historic Structures Precautions:
- Efflorescence may appear after treatment.
- There is a risk of brown ferric hydroxide stains being formed in the presence of iron compounds in the stone.
- Protective clothing and eye protection should be worn to prevent burns, irritation and optic damage.
- Adjacent paint work may be damaged, if not covered or protected.
- See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- 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).
- For additional information on poulticing, see 04455-02-R.
- For general information on the characteristics, uses and problems associated with marble, see 04455-01-S.
- Prosoco, Inc. www.prosoco.com
- Baking soda or some other alkaline cleaner to be used to form the poultice paste: Available from hardware store.
- Liquid laundry bleach for making the paste
- Mineral water
- Plastic sheeting
- Clean dry towels for blotting the area after treatment
A commercial cleaner such as "Stand Off Oil & Grease Stain Remover" (Prosoco), or approved equal.
- Glass or ceramic container for mixing the solution
- Wooden utensil for stirring the ingredients
- Wood or plastic spatula
- Masking tape
- Examine the marble CAREFULLY to determine the cause of staining before proceeding with any cleaning operation.
3.02 ERECTION, INSTALLATION, APPLICATION
NOTE: DO NOT USE BLEACH ON DARK COLORED STONES AS THIS WILL CAUSE THE STONE TO LIGHTEN.
- Protect adjacent painted surfaces.
- Rinse the area to be treated with mineral water.
- Pour the liquid laundry bleach in a glass or ceramic bowl.
- Thoroughly moisten the stained surface with this liquid. Be sure to dampen well beyond the stain.
- 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.)
- 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 clean stone.
- Check the coating for air pockets or voids.
- After the poultice has been applied, cover it with damp cloths to keep the poultice moist.
- Leave the cloths in place overnight.
- Remove the cloths and wet the poultice with mineral water.
- Remove the poultice with a wooden or plastic spatula to avoid scratching the surface.
- Thoroughly rinse the treated area with mineral water, blot, and allow to dry completely.
- If there is residual staining, repeat the procedure.
If using a commercial cleaning product, follow manufacturer's instructions.