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scratch coat[′skrach ‚kōt]
The first layer of plaster applied to a surface; the surface is scratched to improve the bond with the next coat.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
In three-coat plastering, the first coat of plaster, which is then scratched to provide a bond for the second (brown) coat.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.