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Historic Preservation - Technical Procedures

Spectitle:

Cleaning Darkened Or Discolored Travertine

Procedure code:

0440002R

Source:

Apt Bulletin, V. 23, N. 2 (1991), Doebly, Lewin & Aronson

Division:

Masonry

Section:

Stonework

Last Modified:

06/13/2012

Details:

Cleaning Darkened Or Discolored Travertine



CLEANING DARKENED OR DISCOLORED TRAVERTINE


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on cleaning darkened or
         discolored travertine.

    B.   Travertine naturally darkens over time.  The iron
         compounds in the stone, when combined with oxygen,
         eventually produce a dark reddish-brown tone.

    C.   Travertine may also darken from accumulations of
         particulate dirt.

    D.   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).


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.   Synthetic detergent containing sodium dodecylsulphonate
         and marketed for use in home laundry, such as "FAB"
         detergent, or approved equal.

    B.   Sodium Hypochlorite (NaOCl):

         1.   An unstable salt produced usually in aqueous
              solution and used as a bleaching and disinfecting
              agent.

         2.   Other chemical or common names include Bleaching
              solution*; Household bleach*; Laundry bleach*;
              Solution of chlorinated soda*.

         3.   Potential Hazards:  CORROSIVE TO FLESH.

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

         -OR-

         Calcium Hypochlorite (CaCl2O2):

         1.   A white powder used especially as a bleaching agent
              and disinfectant.

         2.   Other chemical or common names include Chlorinated
              calcium oxide; Bleaching powder*; Calcium
              oxymuriate*; Chloride of lime*; Chlorinated lime*;
              Hypochlorite of lime*; Oxymuriate of lime*.

         3.   Potential Hazards:  CORROSIVE TO FLESH; FLAMMABLE
              (WHEN IN CONTACT WITH ORGANIC SOLVENTS).

         4.   Available from chemical supply house, dry cleaning
              supply distributor, drugstore or pharmaceutical
              supply distributor, janitorial supply distributor,
              swimming pool supply distributor, or water and
              sanitation supply distributor.

    C.   Clean, dry cloths

    D.   Clean, potable water

2.02 EQUIPMENT

    A.   Garden hose

    B.   Stiff bristle brushes and/or acrylic mesh pads

    C.   Paint rollers (for large surface areas)

    D.   Squeegees and/or wet/dry shop vacuums.


PART 3---EXECUTION

3.01 PREPARATION

    A.   Surface Preparation:  Conduct test on small area to
         determine time required to remove the soiling without
         overcleaning.

3.02 ERECTION, INSTALLATION, APPLICATION

    NOTE:  THE EFFECTS OF THIS PROCEDURE ARE ONLY TEMPORARY.  THE
    STONE WILL AGAIN, OVER TIME, DARKEN DUE TO THE REFORMING OF
    IRON OXIDE ON THE SURFACE OF THE STONE.

    CAUTION:  ACIDIC AND ALKALINE CLEANERS WILL ETCH TRAVERTINE
    AND MAY INTRODUCE SOLUBLE SALTS INTO THE POROUS MATERIAL.

    CAUTION:  CLEANERS CONTAINING SODIUM CARBONATE OR ACIDIC
    PHOSPHATES ARE HARMFUL TO TRAVERTINE AND CAN DAMAGE THE
    SURFACE.

    NOTE:  WHEN CLEANING, AVOID OVERCLEANING.  AIM FOR ACHIEVING
    85% CLEAN.  MOST DAMAGE OCCURS WHEN ATTEMPTING TO CLEAN THE
    LAST 15%.  

    NOTE:  BEGIN CLEANING BY USING THE GENTLEST METHOD POSSIBLE.
    TEST CLEAN A SMALL AREA BEFORE ATTEMPTING TO CLEAN LARGE
    AREAS.  TEST IN AN INCONSPICUOUS LOCATION.

    A.   Thoroughly wet the surface to be cleaned.

    B.   Apply synthetic detergent in a 1-2% aqueous solution.

         1.   For small areas, scrub the surface with stiff
              bristle brushes and acrylic mesh pads.

         2.   For large areas, apply with paint rollers and allow
              to remain on the surface for the length of time
              determined by previous testing.

    C.   Thoroughly rinse the surface with clean, clear water and
         allow to dry.  For interior applications, contain liquids
         using squeegees and wet/dry shop vacuums.

    D.   If some soiling still remains, scrub with a 5-1/4%
         solution of sodium hypochlorite or calcium hypochlorite,
         or apply cloths soaked in bleach.

         CAUTION:  BLEACH CAN IRRITATE THE SKIN AND CAN CAUSE
         BLISTERING OF EYES AND MUCOUS MEMBRANES.  IT IS ALSO
         TOXIC IF INGESTED.  WASH HANDS THOROUGHLY AFTER USE.

                         END OF SECTION
 


iron staining, travertine staining, reddish-brown stains, dirt