Installation Guide

26
Accelerator . . . . . . . . . . . . . . . . . . . A substance used to shorten or speed up the setting action (time) of the plaster.
Admixture . . . . . . . . . . . . . . . . . . . . A substance other than water, or aggregate added to the plaster to alter its properties.
Aggregate . . . . . . . . . . . . . . . . . . . . An inert material used as a filler or texturing aid.
Anhydrite. . . . . . . . . . . . . . . . . . . . . An anhydrous form of gypsum.
Basecoat. . . . . . . . . . . . . . . . . . . . . . A plaster coat applied over a substrate prior to application of the finish coat.
Blistering . . . . . . . . . . . . . . . . . . . . . Bulging or separation of the wet finish plaster coat away from the base.
Bond . . . . . . . . . . . . . . . . . . . . . . . . . Adhesion between plaster coats or between plaster and substrate produced by mechanical and
chemical properties of the plaster, or intermediate bonding agents applied prior to plastering.
Bonding Agent . . . . . . . . . . . . . . . . An adhesive substance applied to a substrate to provide a medium for plaster bond.
Brown Out . . . . . . . . . . . . . . . . . . . . A darkening of the exposed plaster surface indicating setting action is complete.
Buck-Up . . . . . . . . . . . . . . . . . . . . . . A premature stiffening of plaster mortar shortly after mixing. Usually indicates a plaster deficiency
or an adverse reaction to a job addition of aggregate.
Calcine . . . . . . . . . . . . . . . . . . . . . . . To drive off water of crystallization by heating.
Calcined Gypsum . . . . . . . . . . . . . . Gypsum with 1-1/2 molecules of combined water removed – also called plaster, stucco, hemihydrate, semihydrate.
Cat Face . . . . . . . . . . . . . . . . . . . . . . A blemish or rough depression in the finish coat plaster.
Chemical Bond . . . . . . . . . . . . . . . . Bond produced by the formation and subsequent interlocking of gypsum crystals during the setting process.
Coat. . . . . . . . . . . . . . . . . . . . . . . . . . A thickness, covering, or layer of plaster applied in a single operation.
Consistency . . . . . . . . . . . . . . . . . . . An amount of water required to bring a unit weight of dry plaster to a workable fluidity.
Craze Cracks . . . . . . . . . . . . . . . . . . Fine random fissures or cracks in the plaster surface caused by plaster shrinkage due to loss of water before setting.
Cure. . . . . . . . . . . . . . . . . . . . . . . . . . The state of or conditions conducive to complete hydration of the plaster.
Dolomite . . . . . . . . . . . . . . . . . . . . . A type of lime or limestone containing calcium with up to 50% magnesium as the hydroxide or carbonate.
Double-Up . . . . . . . . . . . . . . . . . . . . Plaster placement characterized by application of material from the same mixed batch in successive
operations without setting or drying allowed between coats – double-back, laid-off, or two-coat work.
Draw-Up. . . . . . . . . . . . . . . . . . . . . . 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.
Dry-Out. . . . . . . . . . . . . . . . . . . . . . . A condition where some or all of the water necessary for plaster hydration is lost by evaporation or excessive suction.
Efflorescence. . . . . . . . . . . . . . . . . . A white, fleecy surface deposit of salts.
Fat . . . . . . . . . . . . . . . . . . . . . . . . . . . Soft usable plaster accumulated on trowel during finishing operation, often used to fill in small imperfections.
Finish Coat. . . . . . . . . . . . . . . . . . . . The last layer of plaster applied – smooth or texture.
Finishing Brushes . . . . . . . . . . . . . . Brushes used to dash water onto the surface of finish plaster during smooth troweling.
Float . . . . . . . . . . . . . . . . . . . . . . . . . Tool or procedure used to straighten and level the finish coat surface to correct surface irregularities
produced by other tools and to impart a distinctive surface texture.
Float Finish . . . . . . . . . . . . . . . . . . . A finish coat texture derived primarily from aggregate particles in the plaster.
Gauging . . . . . . . . . . . . . . . . . . . . . . Gypsum plaster added to lime putty to provide and control set.
Green . . . . . . . . . . . . . . . . . . . . . . . . Newly applied plaster that has set but not completely dried out.
Hawk. . . . . . . . . . . . . . . . . . . . . . . . . Tool used by plasterers to hold and carry plaster mortar, in conjunction with troweling.
Hemihydrate . . . . . . . . . . . . . . . . . . Calcined gypsum.
High Calcium Lime. . . . . . . . . . . . . The oxide or hydroxide derived from limestone, which is principally calcium carbonate.
The product contains less than 5% magnesium oxide or hydroxide.
Hydrate. . . . . . . . . . . . . . . . . . . . . . . Term used to denote hydrated lime.
Hydrated Lime . . . . . . . . . . . . . . . . Quicklime (oxide) which has been hydrated to yield the hydroxide, a dry powder.
Joining . . . . . . . . . . . . . . . . . . . . . . . The juncture of two separate plaster applications on a common surface.
Landplaster . . . . . . . . . . . . . . . . . . . Ground natural gypsum.
Lay Down. . . . . . . . . . . . . . . . . . . . . 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.
Glossary of Terms