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Historic Preservation - Technical Procedures
Treating Bleached Areas On Marble
Stain Removal Guide For Stone - F. M. Hueston
Treating Bleached Areas On Marble
TREATING BLEACHED AREAS ON 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 treating marble which
has been lightened or etched as a result of improper
exposure to bleaching agents. Household bleach contains
the acid Sodium Hypochlorite. All acids can be harmful
to marble materials if they are not sufficiently diluted,
and cleaners containing acids can be harmful to marble by
etching or discoloring the surface.
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).
F. For general information on the characteristics, uses and
problems associated with marble, see 04455-01-S.
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. Oxalic Acid (COOH)2 or (H2C2O4):
1. A poisonous strong acid that occurs in various
plants as oxalates and is used especially as a
bleaching or cleaning agent and in making dyes.
2. Other chemical or common names include Dibasic
acid; Ethanedioic acid; Acid of sugar*.
3. Potential Hazards: TOXIC; CORROSIVE TO CONCRETE,
STEEL, WOOD OR GLASS.
4. Available from chemical supply house, dry cleaning
supply distributor, drugstore or pharmaceutical
supply distributor, hardware store, or photographic
supply distributor (not camera shop). (Often sold
under a manufacturer's brand name; the chemical
name may appear on the label.)
B. Linseed Oil: Available from hardware or paint store.
C. Clean, soft, white cloths
A. Stiff fiber bristle brush
A. Examine the marble surface CAREFULLY to determine the
cause of staining before proceeding with any cleaning
3.02 ERECTION, INSTALLATION, APPLICATION
A. Thoroughly rinse the area with clean, clear water to
remove any bleach remaining on the surface.
B. If the marble surface is etched, repolish the area with
a polishing powder such as aluminum oxide or oxalic acid.
For guidance, see 04455-15-R "Removing Etch Marks in
Marble" followed by 04455-02-P "Repolishing Marble".
C. If the area is lightened, try applying a thin application
of linseed oil to the affected area. This might darken
the stained area so that it is not as noticeable. NOTE:
ALWAYS TEST A SMALL AREA FIRST, AND OBTAIN APPROVAL FROM
RHPO BEFORE PROCEEDING WITH THE TREATMENT OF LARGER
END OF SECTION