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LATH & PLASTER Section 09200 15-1207 C. At the beginning of each day and after each new delivery of sand, use a calibration box to establish how many No. 2 shovels are required to equal one cubic foot for each material. D. Machine -mix for three (3) minutes but never more than five (5) minutes. DO NOT OVERMIX! Clean machine mixer following each batch. Use only freshly mixed materials in good condition. Re -tempering (adding water to dilute a curing and stiffened mix) is not allowed. E. Control plaster system thickness and surface evenness using grounds or screeds. Use temporary screeds or plaster screeds within plastered areas to supplement fixed grounds and screeds. Finish surfaces smooth and even within tolerance of 1/8 inch in 10 feet from true plane. F. Scratch Coat: Apply scratch coat in specified thickness with sufficient material to form good keys, completely embed the lath, and to allow for scoring of cement plaster surface. Lightly score scratch coat horizontally. Moist cure scratch coat, morning and evening, for at least 48 hours (2 days) before applying brown coat. Cover with polyethylene sheets to retard evaporation during extreme heat or windy conditions. Machine application requires approval of Architect. G. Brown coat: Apply brown coat in specified thickness, over damp scratch coat. Apply a fine spray of clean water to cured scratch coat, so as to dampen only. Do not saturate. Allow sheen to disappear before applying the brown coat. Apply brown coat with sufficient material and pressure to ensure a tight uniform bond to scratch coat. Moist cure Brown Coat, morning and evening, for 48 hours (2 days). Cover with polyethylene sheets to retard evaporation during extreme heat or windy conditions. Machine application requires approval of Architect. Brown Coat to be flat within 1/8 inch per 10 feet, one way. 1. The Architect will consider requests to reduce the curing time of the brown coat, as specified for the base or finish coat, upon receiving a written opinion from the Wall and Ceiling Bureau. 2. Any reduction in curing time request will need confirmation of the use of the Moh's Hardness Test to establish a base line hardness of the brown coat. 3. Curing of the brown coat starts after the first wetting, after the final set of the plaster, when the plaster is hard enough to moist cure. H. Waterproof Membrane: No sooner than 28 days following proper application and curing of brown coat, apply over brown at all sloped, non -vertical surfaces in accordance with manufacturer's recommendations. Lap over adjacent vertical surfaces a minimum of 6 inches. Parge Coat (exterior & interior applications): Apply over brown coat where necessary to bring the surface within acceptable tolerances for application of the finish coat. 1. No sooner than 28 days following proper application and curing of brown coat, apply parge coat per manufacturer's recommendations, as required to provide smooth, even surface, and fill voids, not to exceed 1/8" in a single pass. 2. Allow parge coat to cure a minimum of 24 hours until completely dry. Cool, humid conditions may require longer cure times. 100% Acrylic Finish Coat: No sooner than 28 days after proper application and curing of Brown Coat and no sooner than 2 days after application of parge coat/base coat, where occurs, apply 100% Acrylic Finish Coat: 12