A. PROBLEM: Peeling from Mill-Glazed Western Red Cedar or Redwood Siding
CAUSE: Mill-glaze occurs on smooth, flat-grained western red cedar and occasionally on redwood. Controversy exists over the exact cause of this condition, but the general belief is that it occurs as a result of planing and/or drying the lumber. During the milling or planing process, overheating of the flat-grained smooth siding may bring water soluble resins to the surface creating a hard, varnish-like glaze.
SOLUTION: If the surface is unpainted, it is advisable to roughen smooth siding slightly prior to priming. Two coats of primer may be necessary where severe staining exists. A waiting period of 24 hours after application of first primer coat is recommended before applying second coat and/or finish coat. Tannic acid stains will penetrate first coat of primer leaving brownish streaks or rings. If stains do occur, reprime stained spot and dry thoroughly before applying finish coat. For repainting over mill glaze problem areas, remove the failed coating areas by pressure washing or hand scrapping. Sand and prime as recommended above. Newly installed siding should be sanded and primed as soon as possible. Ultraviolet rays from the sun tend to degrade the integrity of the wood's surface. A 50% loss in adhesion occurs on western red cedar weathered for 16 weeks prior to finishing. Bare weathered siding should be sanded prior to coating to remove loose, dead wood fibers caused by extended exposure.
B. PROBLEM: Peeling from Asbestos Shingles
CAUSE: After years of wear, asbestos cement siding can develop a surface layer of fine dust similar to chalk causing paint to peel.
SOLUTION: CHECK FOR LOCAL OR STATE REGULATIONS REGARDING THE REMOVAL OF PRODUCTS CONTAINING ASBESTOS BEFORE TRYING TO CURE THIS PROBLEM!
Loose paint should be removed by pressure washing. Use extreme caution when scraping or sanding asbestos shingles. It is extremely important to wear protective gear to prevent inhaling asbestos dust particles. It is equally important to prevent fibers and dust from entering occupied areas and to prevent accumulations of dust being left for tracking into these areas. After the shingles have completely dried, check for structural integrity. If they remain soft, no coating will offer long term service.
C. PROBLEM: Peeling from Galvanized Metal
CAUSE: * Improper priming of surface. * Chemicals on new, unweathered galvanized surface. * Rusting. * When alkyd or oil-based product is applied over bare galvanized surface, a chemical reaction occurs and a soap film forms between metal and coating.
SOLUTION: Remove all loose, flaking paint down to bare metal. Galvanized metal must be clean, dry, and free of oil or grease. Wipe new metal with mineral spirits to remove any oil film remaining from manufacturing operations.
