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Historic Preservation - Technical Procedures

Spectitle:
Removing Yellow Discoloration From Marble

Procedure code:
0445528R

Source:
Stain Removal Guide For Stone - F. M. Hueston

Division:
Masonry

Section:
Marble

Last Modified:
02/24/2012

Details:
Removing Yellow Discoloration From Marble



REMOVING YELLOW DISCOLORATION 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.


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing yellow
         discoloration from marble surfaces.  Yellowing may result
         from any of the following:

         1.   From the discoloration of waxes or other coatings
              applied to the marble surface.  

         2.   From exposure to ultraviolet light over a long
              period of time.

         3.   From oxidation of iron oxides in the marble.

         4.   From mastics used to set the marble.

    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

         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).

    C.   For general information on the characteristics, uses and
         problems associated with marble, see 04455-01-S.


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Clean, cold water

    B.   Chelating agent such as EDTA (ethylene diamine tetra-
         acetic acid) - used to remove metallic stains from
         masonry.

         1.   The chelating agent serves to keep any iron
              suspended in the water so it does not settle on the
              stone.

         2.   Chelating agents are molecules that coordinate
              metal ions together.  The metal ions in the stain
              attach themselves to the chelating agent to form
              either a soluble or insoluble metal complex that
              can then be removed.

         3.   Available from chemical supply house.

         4.   It is available as an acid or in the form of its
              more soluble sodium salts.  It is known to be used
              as a preservative.  Its most important use,
              however, is in the removal of unwanted metal ions
              from water, as in the manufacturing of agricultural
              chemical sprays.

         5.   FOR USE ON ACID-SENSITIVE MASONRY

         6.   Acid-sensitive masonry includes limestone, marble,
              calcareous sandstone, glazed brick, sand-lime
              brick, architectural terra cotta, and polished
              granite.

2.02 EQUIPMENT

    A.   Stiff bristle brush (non-metallic)


PART 3---EXECUTION

3.01 EXAMINATION

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

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   If the yellowing is caused by oxidation of iron inherent
         in the marble or caused by age, removal of the staining
         will be impossible.  Natural characteristics and aging of
         the stone can not be reversed.

    B.   If the yellowing is caused by the deterioration of waxes
         or other coatings that have been applied to the marble
         surface, strip the coatings from the marble and re-polish
         or re-hone as desired.  See 04455-01-R for guidance on
         removing built-up coatings from marble.  See 04455-02-P
         for guidance on re-polishing marble.

    C.   If the yellowing results from iron deposited on the
         surface from cleaning water that contains high levels of
         iron, try one of the following:

         1.   Wash the stone with water and a chelating agent
              such as EDTA (Ethylene diamine Tetra-acetic Acid),
              or approved equal.  Scrub the surface using a stiff
              bristle brush (non-metallic bristle).

              a.   Allow the cleaner to stand on the surface for
                   approximately 1 hour or as recommended by
                   manufacturer.

              b.   Thoroughly rinse the surface with clean, clear
                   water and allow to dry.


              -or-

         2.   Wash the stone using a commercial rust remover.
              See 04400-06-R for guidance.

                         END OF SECTION