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Historic Preservation - Technical Procedures

Spectitle:

Removing Dirt From Stone Masonry By Steam Cleaning

Procedure code:

0440002P

Source:

Developed For Hspg (Nps - Sero)

Division:

Masonry

Section:

Stonework

Last Modified:

06/13/2012

Details:

Removing Dirt From Stone Masonry By Steam Cleaning



REMOVING DIRT FROM STONE MASONRY BY STEAM CLEANING


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing dirt
           build-up on stone masonry by steam cleaning.  

    B.   Advantages of Steam Cleaning:  

         1.   Is effective in cleaning heavily deteriorated
              ornate masonry that can not withstand pressure
              washing or abrasive cleaning techniques.

         2.   Allows use of the mildest possible cleaning agents
              and rinsing pressures for removal of severe carbon
              encrustations on calcareous surfaces.

         3.   Effective in removing organic growth from the
              masonry surface.

         4.   There is less of a chance of staining as compared
              to other cleaning methods.

    C.   Limitations of Steam Cleaning:  

         1.   This method is more expensive (due to the high cost
              of steam-generating equipment) and requires more
              time than other methods.  

         2.   Excessively high temperatures with this procedure
              is a safety hazard to the operators.

         3.   It is sometimes difficult for the operator to
              monitor his progress due to the cloud of steam
              generated with this technique.

         4.   This method is NOT effective in removing severe
              staining.

    D.   Safety Precautions:  

         1.   Precautions should be taken to guard against
              unnecessary water infiltration.  Monitors should be
              set within the walls to determine moisture content
              and possible problems.

         2.   Soft water should NOT be used on carbonate stone.
              Soft water sometimes contains minerals that can
              bring out impurities in the stone resulting in
              permanent discoloration.  Mildly acidic water can
              also cause carbonate stone to become more soluble
              resulting in the eventual dissolution of the stone.

    E.   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).

    F.   See also 04400-01-P and 04400-03-P for alternative
          guidance on removing dirt from stone masonry.


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.  Dow Chemical
         www.dow.com    
         

    B.  Union Carbide Corporation
         www.unioncarbide.com
         
         
    C.  Ashland Chemical
         www.ashland.com 
                
        
    

2.02 MATERIALS

    A.   Non-ionic detergent such as "Tergitol,
          "Triton, "Igepal", or approved equal.

         1.   Use dilution as approved by testing on material to
              be cleaned.

         2.   Acidic or alkaline products are NOT acceptable.

    B.   Clean, potable water (preferably mineral water)

2.03 EQUIPMENT

    A.   Garden hose and nozzle (approximately 1/2" diameter)

    B.   Non-metallic brushes (no iron or brass wire)

    C.   Wood scrapers

    D.   Flash boiler for generating the steam


PART 3---EXECUTION

3.01 PREPARATION

    A.   Protection:

         1.   Cleaning methods should be tested prior to
              selecting the one for use on the building; The
              simplest and least aggressive methods should be
              selected.

         2.   The level of cleanliness desired should be
              determined; A new appearance look is both
              inappropriate and requires an overly harsh cleaning
              method.

         3.   Prolonged exposure of water causes rapid
              deterioration in older structures.

         4.   Take precautions to ensure that the water does not
              penetrate the surface and cause damage to the
              interior of the structure.

         5.   This procedure may cause corrosion of hidden iron
              work and steel anchors causing either staining or
              cracking due to the rapid expansion of the metal.

         6.   If the masonry remains saturated during the first
              frost, surface pieces may spall off as the water
              freezes.

         7.   Iron and chloride in the water can cause
              disfigurement and staining.

    B.   Surface Preparation:

         1.   Fill the buckets, usually one or two, with about
              two gallons of water.

         2.   Beginning at the top and gradually working down,
              scrub lightly with the fiber brush to remove any
              superficial deposits. Take care to avoid scratching
              or otherwise damaging any polished surfaces.

         3.   Rinse with clear water.

         4.   Dry with clean, lint-free toweling or rags.

         5.   Tenacious mineral deposits may be treated locally
              with gentle abrasion using wooden paddles or
              sticks.  Great care should be exercised to avoid
              damaging the highly polished surfaces of masonry
              where they exist.

3.02 ERECTION/INSTALLATION/APPLICATION

    A.   Direct steam (generated in a flash boiler) against the
         masonry surface.  The heat of the steam will swell and
         soften dirt deposits and loosen them from the masonry
         surface.

         1.   Use a very low-pressure nozzle (10-30 psi)- about
              1/2 inch diameter aperture.  

         2.   Hold the nozzle tip consistently a minimum of 12
              inches from the masonry surface.

    B.  Remove softened dirt by hand, scrubbing with non-metallic
         brushes.  Use a wooden scraper to remove heavy sulphate
         crusts.

   C.   Rinse thoroughly with water until surface tests as neutral as

          indicated with pH strip.


    D.   If steam alone is not effective, it may be supplemented
         with a non-ionic detergent.

                         END OF SECTION
 


dirt, stone, masonry, steam cleaning, hot water cleaning