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Historic Preservation - Technical Procedures

Spectitle:

Surface Preparation For Painting Wood

Procedure code:

0630002R

Source:

Hspg Prepared For Nps - Sero

Division:

Wood And Plastics

Section:

Wood Treatment

Last Modified:

02/24/2012

Details:

Surface Preparation For Painting Wood



SURFACE PREPARATION FOR PAINTING WOOD


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on preparing wood
         surfaces for painting.

    B.   Wood surfaces scheduled to be refinished with a
         transparent finish shall have existing coating stripped
         and sanded prior to application of new coatings.

    C.   Wood surfaces scheduled to be finished with an opaque
         finish (see 06300-01-S) shall either be stripped or
         sanded as required to produce a smooth substrate for
         application of the new coatings.

    D.   For guidance on paint removal from wood, see 06400-07-R
         "Chemically Removing Paint From Wood Features",
         06400-02-S "Supplemental Guidelines for Removing Paint
         from Interior and Exterior Wood Surfaces" and 06400-09-R
         "Removing Paint From Wood Features Using Thermal
         Methods".

    E.   For general information on paint for wood, see 06300-01-S.

    F.   For additional information on the history, properties and
         uses of paint, see 09900-01-S.

    G.   See 09900-07-S for general guidelines on painting
         interior and exterior surfaces.


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   American International Tool Industries, Inc.
         1116-B Park Avenue
         Cranston, Rhode Island  02910
         800/932-5872 or 401/942-7855

    B.   Benjamin Moore and Co.
         51 Chestnut Ridge Road
         Montvale, NJ 07645
         201/573-9600

    C.   The Sherwin-Williams Company
         101 Prospect Ave. N.W.
         Cleveland, OH  44101
         216/566-2000

2.02 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.   Paste Wood Filler:  Solvent-based, air-drying, paste-type
         wood filler for use on open-grain wood on interior wood
         surfaces such as "Benwood Paste Wood Filler" (Benjamin
         Moore and Co.), "Sher-Wood Fast-Dry Filler" (The Sherwin-
         Williams Co.), or approved equal.

    B.   Trisodium Phosphate:  

         NOTE:  THIS CHEMICAL IS BANNED IN SOME STATES SUCH AS
         CALIFORNIA.  REGULATORY INFORMATION AS WELL AS
         ALTERNATIVE OR EQUIVALENT CHEMICALS MAY BE REQUESTED FROM
         THE ENVIRONMENTAL PROTECTION AGENCY (EPA) REGIONAL OFFICE
         AND/OR THE STATE OFFICE OF ENVIRONMENTAL QUALITY.

         1.   Strong base-type powdered cleaning material sold
              under brand names.

         2.   Other chemical or common names include Sodium
              Orthophosphate; Tribasic sodium phosphate;
              Trisodium orthophosphate; TSP*; Phosphate of soda*;
              (also sold under brand names such as).

         3.   Potential Hazards:  CORROSIVE TO FLESH.

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

         -OR-

         Non-ammoniated detergent such as "Tide"

         -OR-

         Liquid bleach containing 5% sodium hypochlorite (common
         household bleach)

    C.   Boiled Linseed Oil

    D.   Turpentine - clean and clear so that it will not
         adversely affect the texture or durability of the paint.

    E.   Caulking Compound (in order of recommended usage):

         1.   Polyurethanes - easily workable; paintable; 15-20
              year life span; limited availability.

         2.   Polysulfides - slow drying; can be sanded and
              painted; highly elastic; limited availability.

         3.   Butyls - paintable but cannot be sanded; 7-10 year
              life span.

         4.   Silicones - some can be painted but generally not
              sanded.

         5.   Acrylic Latex - for exterior work, their use is
              best left to tight, narrow joints; short life span
              especially when compared to polysulfides and
              polyurethanes.

    F.   Clean, potable water

2.02 EQUIPMENT

    A.   Sanding blocks, sanding sponges, orbital sander, all with
         a variety of grits.

    B.   Sanding vacuum such as "S344 Sander Vac" (American
         International Tool Industries, Inc.), or approved equal.

    C.   Stiff, natural and nylon bristle brushes


PART 3---EXECUTION

3.01 PREPARATION

    A.   Protection:  Spot-prime exposed ferrous metals such as
         nails on or in contact with surfaces to be painted with
         water-based paints.  Use a suitable corrosion-inhibiting
         primer capable of preventing flash rusting and compatible
         with the coating being used.  

    B.   Surface Preparation:

         1.   Lightly sand all surfaces, either by hand or with
              an orbital sander, using fine grade sandpaper.

              CAUTION:  WORKERS SHOULD USE PROTECTIVE CLOTHING
              AND RESPIRATORS FOR PROTECTION AGAINST
              CONTAMINATION WITH LEAD DUST.

              NOTE:  CHEMICAL REMOVERS MAY RAISE THE GRAIN OF THE
              WOOD.  SUCH ROUGH FIBERS WILL WEAKEN THE PAINT FILM
              CAUSING PREMATURE PAINT FAILURE.  THERMAL METHODS
              OFTEN LEAVE BEHIND HARD PARTICLES OF PAINT RESIDUE
              WHICH ALSO NEED TO BE REMOVED TO ENSURE A SMOOTH
              FINISHED SURFACE.

         2.   If only limited paint removal is required, feather
              edges of sound paint to provide a smooth transition
              between the old and the new paint.  Use either hand
              methods or an orbital sander.

              NOTE:  BELT SANDERS SHOULD ONLY BE USED BY
              EXPERIENCED PERSONNEL.  THEY WORK VERY QUICKLY AND
              IT IS EASY TO DAMAGE THE WOOD SUBSTRATE IF THEY ARE
              NOT USED CAREFULLY.

              NOTE:  SANDING DUST MAY CONTAIN LEAD; USE SANDING
              EQUIPMENT EQUIPPED WITH A SANDING VACUUM TO PREVENT
              LEAD DUST FROM GETTING INTO THE AIR.  FOLLOW OTHER
              REGULATIONS PROVIDED BY THE EPA REGIONAL OFFICE
              AND/OR THE STATE OFFICE OF ENVIRONMENTAL QUALITY
              CONCERNING THE HANDLING OF LEAD-BASE PAINT.

         3.   Scrape and clean small, dry, seasoned knots and
              apply a thin coat of white shellac or other
              recommended knot sealer before application of putty
              or plastic wood filler to finish surface
              imperfections.  Sand smooth when dried.

         4.   Fill all nail holes, voids, surface defects, etc.
              prior to refinishing.

              a.   Putty stop holes where nails are set and
                   screws countersunk on all finished woodwork.

              b.   Include puttying or spackling repairs to
                   voids, cracks, minor splits, and similar
                   surface defects in finished woodwork to be
                   painted or stain-varnish finished.

         5.   Recondition wood to ensure a tight bond between the
              new paint and the wood.  Wood that is not
              reconditioned after paint removal is often left
              very dry and, therefore, may absorb too much of the
              binder in the paint resulting in poor binding of
              the prime coat.  

              a.   Mix 2 parts boiled linseed oil with 1 part
                   turpentine.  

              b.   Apply liberally with a brush and allow to dry.

              c.   Repeat as necessary until dry surface has a
                   slight sheen.

         6.   If all paint has not been removed, wash the painted
              surfaces to remove all grease, dirt and mildew, and
              to insure adequate adhesion of the prime coat.  

              a.   Wash dirt and grease using a solution of 3
                   quarts warm water mixed with 2/3 cup trisodium
                   phosphate (TSP) and 1/2 cup non-ammoniated
                   detergent.  

              b.   If mildew is a problem add 1 quart of liquid
                   bleach.  For stubborn mildew, straight bleach
                   may be necessary.  Scrub surfaces with a
                   medium bristle brush and rinse with clean,
                   clear water.  Make sure the surface is
                   completely rinsed before painting.  

              NOTE:  WHEN TSP IS MIXED WITH WATER IT FORMS FREE
              ALKALI.  THIS FREE ALKALI WILL CAUSE OIL-BASED
              PAINTS TO BECOME SOAPY SO THAT THEY WILL NOT STICK
              TO THE SUBSTRATE.  RINSE THOROUGHLY WITH CLEAN
              WATER BEFORE PROCEEDING.  (CHECK LABEL FOR
              INGREDIENTS.  SODIUM CARBONATES FOUND IN SOME
              DETERGENTS HAVE SIMILAR PROBLEMS.)

              CAUTION:  DO NOT MIX AMMONIA WITH CHLORINE
              BLEACHES, A POISONOUS GAS WILL RESULT!  DO NOT USE
              BLEACH ON BIRD DROPPINGS.

         7.   Apply a Water Repellent (WR) or Water Repellant
              Preservative (WRP) (See 06310-01-S and 06310-01-P
              for guidance on preparation and application).

              NOTE:  THIS TREATMENT IS RECOMMENDED FOR EXTERIOR
              ITEMS SUBJECT TO EXTREME WEATHERING CONDITIONS, OR
              WHICH ARE ESPECIALLY DRY OR MAY HAVE BEEN
              CONSOLIDATED.  SOME OF THESE EXTERIOR ITEMS MAY
              INCLUDE WINDOWS, CORNICES, OR OTHER ITEMS WHICH MAY
              HAVE HAD SEVERELY PEELING PAINT AND EXPOSED WOOD
              FOR A NUMBER OF YEARS.  

              NOTE:  ALL UNPAINTED WOOD WHICH IS TO BE REPAINTED
              USUALLY BENEFITS FROM THE APPLICATION OF EITHER A
              WR OR A WRP.  

         8.   Caulk any end grain wood subject to water
              infiltration.  Also, caulk where wood trim pieces
              or door and window frames meet wall surfaces.

         9.   Wood trim which has been removed, or new pieces to
              be installed, may be "back-primed" or painted along
              the end grain for additional moisture-proofing.
              When transparent finish is required, backprime with
              spar varnish.

                         END OF SECTION