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Historic Preservation - Technical Procedures

Spectitle:

Removing Mildew Stains From Marble

Procedure code:

0445526R

Source:

Stain Removal Guide For Stone - F. M. Hueston

Division:

Masonry

Section:

Marble

Last Modified:

07/30/2013

Details:

Removing Mildew Stains From Marble



REMOVING MILDEW 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.


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing mildew from
         marble surfaces.  Mildew stains from fungus, algae or
         other living plants are typically black, green, blue,
         orange or blotchy white in color and tend to disappear
         when the offending object has been removed.  This
         procedure may be used to remove those stains which
         remain.

    B.   Biological growths such as lichens, algae, moss and fungi
         growing on stone masonry walls is usually an indication
         that there is excess moisture in or around the stone
         masonry.  These growths should be removed, as they
         attract moisture to the masonry surface and hold it
         there, which can lead to more serious problems.  Lichens
         and mosses in particular, produce oxalic acid which can
         damage certain types of historic masonry.

    C.   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).

    E.   For information on removing other organic stains from
         marble, see 04455-14-R.

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


PART 2---PRODUCTS

2.01 MATERIALS

    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.   Household Bleach:

         1.   Other chemical or common names include Bleaching
              solution*; Laundry bleach*; Sodium Hypochlorite
              (NaOCl); Solution of chlorinated soda*.

         2.   Potential Hazards:  CORROSIVE TO FLESH.

         3.   Available from chemical supply house, grocery store
              or supermarket, hardware store or janitorial supply
              distributor.

    B.   Mild dishwashing detergent such as "Ivory Liquid", "Joy",
         or approved equal.

    C.   Clean, potable water

    D.   Clean dry towels for blotting the area after treatment

2.02 EQUIPMENT

    A.   Plastic spray bottle


PART 3---EXECUTION

3.01 EXAMINATION

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

    B.   Test cleaning procedure in a small inconspicuous area to
         determine the effectiveness of the treatment.  If the
         stain/mildew is not removed, contact a stone specialist
         or consult RHPO.  Some biological stains are very
         difficult to identify and require laboratory analysis.

3.02 PREPARATION

    A.   Protection:  Provide adequate wash solutions (i.e. water,
         soap and towels) before starting the job.

3.03 ERECTION, INSTALLATION, APPLICATION

    NOTE:  DO NOT USE BLEACH ON DARK COLORED STONES AS THIS WILL
    CAUSE THE STONE TO LIGHTEN.

    A.   Thoroughly rinse the area to be treated with clean, clear
         water.

    B.   Mix a solution of 3 parts household bleach with 1 part
         water and a dash of dishwashing detergent in a spray
         bottle.

    C.   Thoroughly moisten the stained surface with this liquid
         by misting the surface using the spray bottle.

    D.   Mist the surface continuously until the stain disappears.

    E.   Rinse the surface with clean, clear water and allow to
         dry.

    F.   Once the surface has dried completely, check for
         remaining residue and repeat the treatment if necessary.

    G.   For alternative guidance in removing biological growth
         from masonry, see 04200-02-R.

                         END OF SECTION
 


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