Removing Mortar Deposits And Stains From Marble
REMOVING MORTAR DEPOSITS AND STAINS FROM MARBLE
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.
A. This procedure includes guidance on removing mortar
deposits or other concrete-based residues from marble.
Mortar deposits may be spattered onto adjacent surfaces
during repointing or other repair work. If left on the
surface, these deposits and residual film can be
difficult to remove.
B. 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
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).
C. For guidance on the general cleaning of marble, see
D. For general information on the characteristics, uses and
problems associated with marble, see 04455-01-S.
A. ProSoCo, Inc.
NOTE: Chemical products are sometimes sold under a common
name. This usually means that the substance is not as pure as
the same chemical sold under its chemical name. The grade of
purity of common name substances, however, is usually adequate
for stain removal work, and these products should be purchased
when available, as they tend to be less expensive. Common
names are indicated below by an asterisk (*).
A. Hydrochloric Acid (30-35%):
1. A strong corrosive irritating acid.
2. Other chemical or common names include Chlorhydric
acid; Hydrogen chloride; Muriatic acid* (generally
available in 18 degree and 20 degree Baume
solutions); Marine acid*; Spirit of salt*; Spirit of
3. Potential Hazards: TOXIC, CORROSIVE TO FLESH;
CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS,
FLAMMABLE. CAN CAUSE ETCHING OF POLISHED MARBLE.
4. Available from chemical supply house, drugstore or
pharmaceutical supply distributor, or hardware
B. Clean, potable water
C. Liquid Marble Cleaner: A water-soluble non-acidic
chemical cleaner manufactured specifically for
restorative type cleaning of polished and honed marble
surfaces. Cleaner shall contain no abrasives, grease,
lye, or other caustic or corrosive ingredients, such as
"Sure Klean 942 Limestone and Marble Cleaner" (ProSoCo, Inc.) or
approved equal. May damage highly polished surfaces, do test sample area.
D. Drying Materials: Clean natural fiber rags
A. Garden hose and nozzle
B. Stiff bristle brushes (non-metallic)
C. Wood or plastic scraper
A. Examine the marble surface CAREFULLY to determine the
cause of staining before proceeding with any cleaning
1. Provide adequate wash solutions (i.e. water, soap
and towels) before starting the job.
2. Whenever acid is used, the surface should be
thoroughly rinsed with water as soon as its action
has been adequate. Otherwise it will continue
etching the masonry even though the stain is gone.
3.03 ERECTION, INSTALLATION, APPLICATION
NOTE: TEST CLEAN A SMALL AREA BEFORE ATTEMPTING TO CLEAN
LARGE AREAS. LET TEST AREA REST FOR SEVERAL WEEKS AND EXAMINE TO DETERMINE IF ANY ADVERSE IMPACTS. SEEK ADVICE FROM THE RHPO.
A. If possible, remove large pieces of mortar deposits using
a wood or plastic scraper.
B. For light staining: Clean the surface with a commercial
stone cleaner and water. Follow manufacturer's
C. For more difficult staining:
1. Wash down the affected area with a diluted solution
of hydrochloric acid. CAUTION: HYDROCHLORIC ACID
CAN SEVERELY ETCH POLISHED MARBLE SURFACES. USE
EXTREME CAUTION AND FOLLOW MIXING INSTRUCTIONS
a. For textured stone, mix 1 part hydrochloric
acid with 20 parts water.
b. For polished stone, mix 1 part hydrochloric
acid with 40 parts water.
2. Agitate the treated surface with a stiff fiber
3. Thoroughly rinse the surface with clean, clear
water and allow to dry.
4. If necessary, re-hone or re-polish the surface.
See 04455-02-P for guidance on re-polishing.
END OF SECTION