Interior System Preparation – 9.2 <strong>INT</strong> 9.2 PLASTER AND GYPSUM BOARD Remove sand, dust, dirt, oil, grease, wax, silicone, glue, and all other foreign matter. Any defects apparent before, and after, the primer coat has been applied shall not be the responsibility of the Painting Contractor. The resulting surface must be made acceptable to the Painting Contractor before application of the finish coat(s). Drywall Defects Many defects in the drywall substrate cannot be seen until after the primer, and in some cases, the intermediate coat, have been applied. This condition in drywall is not connected with the quality of either the paint or its application. In addition, structural deficiencies in studding and improperly applied drywall can cause other problems such as "nail popping", ridging, pinholes, etc. Latex primer sealers are flat in appearance, and deficiencies can be hard to detect, particularly under low lighting conditions. However, when materials with a slight to high gloss are applied, the deficiencies in the drywall are very noticeable. At this point, the drywall contractor should be obligated to correct all remaining imperfections. Joint Fillers The Painting Contractor should be cautious when painting drywall (gypsum board), as some of the new type of joint fillers on the market may have an alkali content too high for normal paint coatings. Some lightweight joint fillers are so porous, they require refilling, different filler, or the addition of an extra coat of sealer or finish coating, none of which was called for in the painting specifications. This should not be the financial responsibility of the Painting Contractor. Only top line primer sealers with excellent sealing properties must be used. Recycled paper, often used to produce drywall facings, may require additional preparation such as careful sanding and the application of an additional coat of primer sealer to eliminate suction spots etc. Stain blocking or alkyd based sealers may be required to block the leaching of water soluble materials occasionally found in recycled paper. Plaster Newly applied plaster must cure a minimum of 30 days at 75° F (24° C). The surface must then be tested for alkalinity (See 1.2 pH Testing). Wash and neutralize high alkali surfaces where they occur. Any imperfection in the plaster must be corrected by the plaster trade. Large holes, cracks, joints and other visible imperfections, must be corrected before surfaces will be accepted. Paint should not be applied until repaired surfaces are completely dry. After the application of the primer coat, fill minimal cracks, holes and imperfections, and sand smooth to match adjoining surfaces. Moisture readings must be taken to assure that no more then 12% moisture is in the plaster at the time of the coatings application. Porous areas that show suction spots must be double primed. Environmental conditions before and during application and during drying should be as outlined (See 1.1 Environment). Where plaster “hot spots” or questionably cured plaster surfaces are encountered, the use of an alkali resistant sealer, such as MPI #3, is recommended.
MPI Approved Product # 50 MPI #50 Interior Latex Primer Sealer A white, pigmented, waterborne latex sealer used on new interior plaster, concrete and gypsum wallboard surfaces that are subsequently painted with latex or alkyd finish coat(s). Its purpose is to reduce the porosity of the substrate for finish coats. Not intended for use on wood. [Evaluated characteristics include consistency/viscosity, dry time, fineness of grind, hiding power by contrast ratio method, reflectance, alkali resistance holdout properties, and sanding properties. See MPI ‘Detailed Performance’ Specs for complete details, specific requirements, and/or reference specs.] MPI VOC Ranges (grams/L.) E3
Change language