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 |
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