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Historic Preservation - Technical Procedures

Spectitle:

Removing Dirt Build-Up From Slate Shingles

Procedure code:

0731502R

Source:

Unknown

Division:

Thermal And Moisture Protection

Section:

Slate Shingles

Last Modified:

02/24/2012

Details:

Removing Dirt Build-Up From Slate Shingles



REMOVING DIRT BUILD-UP FROM SLATE SHINGLES


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing surface dirt
         from slate shingles.

    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).


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.   For Light Dirt:

         1.   Murphy's oil soap

    B.   For Heavy Dirt Build-up and Staining:

         1.   Oxalic Acid (COOH)2 or (H2C2O4):

              a.   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.

              b.   Other chemical or common names include
                   Ethanedioic acid.

              c.   Potential Hazards:  TOXIC; CORROSIVE TO
                   CONCRETE, STEEL, WOOD OR GLASS.

              d.   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.)

         -OR-

              Muriatic Acid (generally available in 18 degree and
              20 degree Baume solutions):

              a.   A strong corrosive irritating acid.

              b.   Other chemical or common names include
                   Chlorhydric acid; Hydrochloric acid (30-35%);
                   Hydrogen chloride; Marine acid*; Spirit of
                   salt*; Spirit of sea salt*.

              c.   Potential Hazards:  TOXIC, CORROSIVE TO FLESH;
                   CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS,
                   FLAMMABLE.

              d.   Available from chemical supply house,
                   drugstore or pharmaceutical supply
                   distributor, or hardware store.

    C.   Clean, potable water

2.02 EQUIPMENT

    A.   Clean, soft cloths

    B.   Stiff bristle brush


PART 3---EXECUTION

3.01 ERECTION, INSTALLATION, APPLICATION

    A.   For Light Dirt:

         1.   Apply Murphy's oil soap to the slate and rub with a
              clean, soft cloth.

         2.   Thoroughly rinse the slate with clean, clear water
              and allow to dry.

    B.   For Heavy Dirt Build-up and Staining:

         1.   Mix oxalic acid with water using proportions
              recommended by manufacturer.

              -OR-

              Mix 1 part muriatic acid with 3 parts water.

              CAUTION:  ALWAYS WEAR RUBBER GLOVES AND SAFETY
              GLASSES WHEN WORKING WITH ACID; ALWAYS POUR ACID
              INTO WATER (NEVER THE REVERSE); KEEP A PAIL OF
              WATER HANDY TO QUICKLY NEUTRALIZE ANY DAMAGE CAUSED
              BY SPILLAGE.

         2.   Apply the cleaning solution to the slate and rub
              with a clean, soft cloth.  Use a stiff bristle
              brush to aid in dirt removal.

         3.   Thoroughly rinse the slate with clean, clear water
              and allow to dry.

         4.   Repeat as necessary to achieve the desired level of
              cleanliness.

                         END OF SECTION