A. Robin Raymer of Plasterzone.com, an author, educator, and veteran plastering contractor, responds: Plaster-base gypsum board — or blue board — is designed for veneer-coat plaster. It has an absorbent paper face that draws moisture out of the plaster as it sets. The paper chemically reacts to the plaster applied over it, strengthening the bond between the plaster and the blue board.
Regular gypsum board — drywall — has the same core, but the paper face is slicker and less absorbent so that moisture in the joint compound dries to the air rather than being absorbed by the board. Regular gypsum board is sometimes hung with the back facing out in the mistaken belief that this gives the board more suction and gripping power for...
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