Installation Guide

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Lean Mixture. . . . . . . . . . . . . . . . . . High aggregate to plaster ratio; often exhibits poor working qualities.
Light Weight Aggregate . . . . . . . Expanded perlite or vermiculite.
Lime. . . . . . . . . . . . . . . . . . . . . . . . . . Oxides or hydroxides of calcium or calcium and magnesium.
Lime Putty . . . . . . . . . . . . . . . . . . . . A thick paste obtained by “slaking” quicklime or soaking and mixing hydrated lime with a minimum of water.
Mechanical Bond . . . . . . . . . . . . . . Physical keying of plaster to substrate.
Mill Mixed . . . . . . . . . . . . . . . . . . . . Plasters requiring only water addition on the job site.
Mortar . . . . . . . . . . . . . . . . . . . . . . . A material used in plastic state which can be troweled and hardens after placement.
Mud Cracks . . . . . . . . . . . . . . . . . . . Fine random cracks in the plaster surface caused by plaster shrinkage due to loss of water (dry-out) before setting.
Perlite . . . . . . . . . . . . . . . . . . . . . . . . A siliceous volcanic glass – expanded by heating into a lightweight plaster aggregate.
Plaster Bond . . . . . . . . . . . . . . . . . . Adhesion between plaster coats or between plaster and a plaster substrate produced by a mechanical
and chemical interlocking of plaster with the substrate.
Purity . . . . . . . . . . . . . . . . . . . . . . . . The percentage of calcium sulfate dihydrate contained in a fully hydrated gypsum plaster.
Relative Humidity . . . . . . . . . . . . . The ratio of the amount of water vapor actually present in the air to the greatest amount possible
at the same temperature, expressed as a percentage.
Retarder. . . . . . . . . . . . . . . . . . . . . . A material added to plaster which will lengthen the setting time.
Retemper. . . . . . . . . . . . . . . . . . . . . To mix additional water with plaster which has begun to stiffen or set so as to render it workable again.
Sand . . . . . . . . . . . . . . . . . . . . . . . . . A washed and size-graded, granular natural material (aggregate) added to veneer plasters to aid float
texturing of the plaster.
Scratch And Double. . . . . . . . . . . . Plaster application characterized by a tight application of plaster against the substrate and immediately
followed by a second application of plaster from the same batch of mixed plaster.
Setting Time . . . . . . . . . . . . . . . . . . The elapsed time after mixing with water for the plaster to harden or hydrate.
Sweeten . . . . . . . . . . . . . . . . . . . . . . The troweling process after the applied finish plaster has “taken up”, whereby surface irregularities are filled
and leveled with or without the use of fresh plaster on the tools.
Take-Up . . . . . . . . . . . . . . . . . . . . . . A normal stiffening of the applied plaster resulting from the removal of water from the plaster by absorption
(suction) into the substrate.
Trowel Finish. . . . . . . . . . . . . . . . . . Denotes a smooth finish surface produced by troweling.
Veneer Plaster . . . . . . . . . . . . . . . . A specially manufactured gypsum plaster which provides strength, hardness and abrasion resistance and
is capable of thin application over designated substances.
Veneer Plaster Base . . . . . . . . . . . A gypsum board with special paper facing designed to provide water absorption for rapid veneer plaster
application and finishing.
Workability . . . . . . . . . . . . . . . . . . . The ease and speed with which plaster mortar can be applied and finished.