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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:

01/23/2015

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.    www.paintshaver.com

            B.   Benjamin Moore Co      www.benjaminmoore.com

            C.   Pittsburgh Paints    www.ppgpittsburghpaints.com

            D.  The Sherwin Williams Co.       www.sherwin-williams.com

             E.  Glidden Coatings and Resins    www.glidden.com

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 (TSP):  TSP 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.  IT IS A LEGACY PRODUCT AND ITS USE TODAY SHOULD BE CAREFULLY CONSIDERED.  See the MSDS for a TSP-based cleaner at http://www.dap.com/docs/msds/00079403001_english.pdf

              a.   TSP is a strong base-type powdered cleaning chemical sold under several brand names.

              b.   Other chemical or common names include Sodium Orthophosphate; Tribasic sodium phosphate; Trisodium orthophosphate; TSP*; Phosphate of soda.  Available from chemical supply house, grocery store, supermarket or hardware store.

               c.   Products sold as TSP substitute contain may soda ash (sodium carbonate) and/or zeolites. However, sodium carbonate is not as strongly basic as trisodium phosphate, making it less effective in demanding applications.  Zeolites are used in laundry detergents and rapidly break down in water, claiming to be essentially nonpolluting. 

              c.   Potential Hazards: Inhalation risks from TSP result in burning sensations, coughs, shortness of breath, and sore throat. TSP is corrosive to flesh, causing severe burns and blisters, and is damaging to the eyes. 

              d.   Safety Precautions:  Wear proper personal protective equipment, avoid inhalation, contact with skin and eyes, and do not ingest.

         -OR-

         Non-ammoniated detergent such as "Tide"

         -OR-

         Liquid bleach containing 5% sodium hypochlorite (common household bleach, such as ���������Clorox��������� or ���������Javex���������)

    C.   Boiled Linseed Oil

    D.   Pure steam-distilled 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.[1]

         2.   Polysulfides - slow drying; can be sanded and painted; highly elastic; limited availability (most frequently used for marine repairs).

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

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

         5.   Acrylic Latex ��������� In the past, their use on exteriors was best left to tight, narrow joints; and its short life span compared to polysulfides and polyurethanes was a detriment.  That being said, the chemistry involved with improving the properties of latex caulks in recent years has made great strides, and its mating with silicone and other adhesives has stretched its capabilities, with some companies offering a lifetime guarantee on their latex caulk products.[2]

    F.   Clean, potable water

2.02 EQUIPMENT

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

    B.   HEPA-rated Sanding vacuum.

    C.   Stiff, natural and nylon bristle brushes

PART 3---EXECUTION

3.01 PREPARATION

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

    B.   Lead paint hazards

SANDING DUST MAY CONTAIN LEAD; REGULATIONS PROVIDED BY THE EPA REGIONAL OFFICE AND/OR THE STATE OFFICE OF ENVIRONMENTAL QUALITY CONCERNING THE HANDLING OF LEAD-BASE PAINT MUST BE FOLLOWED.

SURFACES SHOULD BE TESTED FOR LEAD CONTENT IN ADVANCE OF WORK.  IF THE TEST IS POSITIVE AND YOU ARE NOT CERTIFIED TO HANDLE LEAD-ABATEMENT TASKS IT IS ILLEGAL FOR YOU TO PERFORM FURTHER WORK. As of 2010, those who perform indoor or outdoor renovation, repair, and painting projects that disturb lead���������based paint in various facilities that were built before 1978 must be certified, trained, and follow specific work practices to prevent lead contamination. Violators can be fined up to $37,500 per occurrence, per day.

For further lead paint handling information see:

EPA: Learning about lead. http://www2.epa.gov/lead

EPA: The EPA Lead Renovation, Repair & Painting Program -  http://www2.epa.gov/lead/renovation-repair-and-painting-program  

EPA: Required contractor training for abating lead paint http://cfpub.epa.gov/flpp/searchrrp_training.htm

HUD: Lead paint Safety, A field Guide for Painting, Home Maintenance & Renovation Work -  http://www.hud.gov/offices/lead/training/LBPguide.pdf

NCPTT: Lead paint & Historic Buildingshttp://ncptt.nps.gov/wp-content/uploads/2002-07.pdf

Building Research Council: A Teacher���������s Guide to Lead Paint & Historic Buildings ��������� Publication SP-19 http://brc.arch.uiuc.edu/Pubcatalog.htm#special%20pubs

C. Surface Preparation:

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

              NOTE:  CHEMICAL REMOVERS MAY RAISE THE GRAIN OF THE WOOD, AND 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. Paint removal utilizing a steam generator (like those used for wallpaper removal) has been very successfully documented in recent years, and does not generate the fumes that other methods do.[3]  Infared paint stripping has also been perfected in the last decade, and when properly utilized this method meets EPA guidelines for lead paint removal.[4]

         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 a ������ sheet 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.

        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 pure steam-distilled 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.   The traditional method to achieve this would be to wash the 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.  Before attempting this, be sure to read the TSP cautions at 2.02 B. at the top of this technical procedure, and consider other options to TSP use..

              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 BLEACH AS A POISONOUS GAS WILL RESULT!  For the same reason, do not utilize 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 WATER REPELLENT OR A WATER REPELLENT PRESERVATIVE. 

         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
 


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