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COPY SOCIAL SECURITY BUILDING Federal Works Agency Public Buildings Administration Washington, D.C. Office of the Supervising Architect September 20, 1940. McNulty Bros. Company c/o McCloskey & Company 3rd & Independence Avenue, S.W. Washington, D.C. Attention Mr. Parrott Gentlemen: We have reviewed the samples of white river sand, lime putty and brick dust submitted by you for the scratch coat of plaster for the mural spaces in the above building. The river sand is considered too fine and the brick dust too course for the purpose. The river sand should be screened and should be of the size which could pass through a number 12 screen but will be retained by a number 16 screen. The brick dust should be of the size that will pass through a number 16 screen. Provided the sand and brick dust are screened accordingly the samples will be satisfactory. The lime putty is also satisfactory. The following information is offered you in connection with mixing and laying on the scratch coat: Foundation Coats or Scratch Coat Consists of one part rough sand #16 and one part crushed brick- to be mixed together dry. To this mixture is added one part of slacked lime. It may be necessary to make this coat a little ricker [[richer]] in lime, depending on the quality of the lime. The parts used in measuring are by volume and not by weight. The scratch coat must be well mixed, allowed to stand for at least twenty-four hours and must be covered in water to prevent drying out. Before laying on the scratch cot it should be mixed well again; this is most important. The wall must be thoroughly moistened with plenty of water and after having been allowed to absorb well into the wall the first coat may be laid on about 1/2" thick. This coat must be of even thickness, any filling of the walls' contours should be made in the brown coat. In laying plaster plenty of pressure should be used in order to