A material that shortens the setting time of

gypsum plasters and other cementitious

materials.

Sound-absorbing plaster formulated for

application where reduction in sound

reverberation or intensity is required.

Any substance added to a plaster component

or plaster mortar for the purpose of modifying

its properties.

An inert granular material, usually silica sand,

limestone, perlite or vermiculite, which may

be added to gypsum plaster on the job, or is

present in mill-prepared plaster. Fiber may be

considered to be an aggregate.

A condition associated with machine gypsum

plaster application, where the sand (usually)

aggregate segregates, or “falls out of,” the

cementitious slurry during pumping; the

plaster or stucco is therefore referred to as

having poor sand “carrying” capacity or

quality.

The process by which air in the form of small

isolated bubbles is introduced into a mortar

while in a liquid or plastic state.

A massive, dense, crystalline, softly textured

form of nearly pure gypsum.

See: Craze Cracks.

A classification of specially processed

calcined gypsums of low consistency and

high strength.

A plaster finishing tool having a surface bent

to form a right angle; used to finish interior

angles.

See: Plaster Base.

Any plaster coat applied over lath or other

substrate prior to application of the finish coat

of plaster. See also Scratch Coat and Brown

Coat.

A preformed metal screed with perforated or

expanded flanges to provide a ground for

plaster, and to separate areas of dissimilar

materials.

A strip of sheet metal, usually formed with a

projecting nosing and one or two perforated

or expanded flanges. Nosing provides the

plaster base; e.g., corner bead, casing bead,

base bead, etc.

See: Joint Deformation.

A coat of plaster (usually portland cement

exterior stucco) to receive lump aggregate or

other coarse decorative material. This

aggregate is embedded into the soft plaster

prior to set.

See: Watering Out.

A condition characterized by bulging of the

finish coat layer as it separates and draws

away from the basecoat.

A subjective and often misused term relating

to the working properties of a plastic

cementitious mass such as gypsum or

portland cement plaster, generally referring to

the relative stiffness or resistance to

movement under the trowel.

A material applied to a surface to improve the

quality of bond between it and succeeding

plaster application.

See: Delamination.

A specially formulated gypsum plaster applied

over monolithic concrete as a bonding coat

for subsequent plaster application.

The second layer in three-coat plaster

application.

1. To apply the second layer or brown coat of

a three-coat plaster application.

2. The visual darkening of a plaster surface

which indicates the completed setting

(hydration) of the plaster.

A condition associated with lime putty, veneer

and other plastering materials characterized

by poor workability or stiffness well before

normal setting. This condition may be related

to exposure of the dry material (open bag)

prior to wet mixing; use of material beyond

published shelf life; or rapid dispersion of

particles within the plaster when mixed in

water.

The weight of a material per unit volume

expressed as pounds per cubic foot (lb./ft.3)

or kilograms per cubic meter (kg/m3).

or kilograms per cubic meter (kg/m3).

A special formed rounded external angle with

a radius of 1/29 (12.5 mm) or more; usually

associated with Tudor or Spanish

architecture.

associated with Tudor or Spanish

architecture.

associated with Tudor or Spanish

architecture.

1. Color imperfections in a lime putty finish

coat that smear out under trowel pressure.

2. An interior corner angle trowel (see Corner

Tool).

A special configuration mixing tool designed

to provide high-shear mixing action with

minimum air-entrainment in veneer plaster

mixing. Provides quick and efficient

dispersion of plaster additives to achieve

optimum mortar plasticity.

To drive off chemically combined water or

carbon dioxide (CO2) by heating. With

gypsum, combined water is driven off in

calcination to yield stucco (CaSO4 • 1/2H2O)

or dead-burned gypsum (CaSO4). In limestone

calcination, carbon dioxide is lost to form

quicklime (CaO) or dolomitic quicklime

(CaO • MgO).

gypsum, combined water is driven off in

calcination to yield stucco (CaSO4 • 1/2H2O)

or dead-burned gypsum (CaSO4). In limestone

calcination, carbon dioxide is lost to form

quicklime (CaO) or dolomitic quicklime

(CaO • MgO).

or dead-burned gypsum (CaSO4). In limestone

calcination, carbon dioxide is lost to form

quicklime (CaO) or dolomitic quicklime

(CaO • MgO).

calcination, carbon dioxide is lost to form

quicklime (CaO) or dolomitic quicklime

(CaO • MgO).

calcination, carbon dioxide is lost to form

quicklime (CaO) or dolomitic quicklime

(CaO • MgO).

Partially or fully dehydrated gypsum used as a

cementitious base for gypsum plaster.

A single-flange bead used as a plaster stop

and as exposed trim around windows and

door openings; also used at junction or

intersection of plaster and other wall or ceiling

finishes.

See: Moulding Plaster.

Blemish or rough depression in the finish coat

caused by variation in basecoat thickness,

poor finish coat mixing, and/or poor

application technique.

A material or mixture of materials that, when

in a plastic state, possesses adhesive and

cohesive properties and which will set in

place.

A component of plaster (gypsum, portland

cement, etc.) that, when mixed with water,

provides plasticity required for placement. On

setting, it serves to bind aggregate and filler

particles together, forming a rigid

heterogeneous mass.

Variously defined as plaster containing

portland cement.

See: Craze Cracking.

See: Craze Cracking.

Fine cracks in a finish plaster coat similar to

craze cracks except that bond is partially

destroyed, producing concave fragments of

the finish.

A thickness or layer of plaster applied in a

single operation.

The line at which, or the method by which,

two separate plaster applications are jointed

to provide a continuous plane surface. The

first application (set, but not dry) is terminated

at a sharp line using the trowel edge. The

second application is brought up to the line of

set material and finished to provide a smooth

continuous surface. This method is used

where termination of a plaster application at

an edge, angle, control joint or bead is

impractical.

A plaster finish coat containing integrally

mixed color pigments or colored aggregates.

Water chemically retained as water of

crystallization; e.g., in calcium sulfate

dihydrate (gypsum) or calcium sulfate

hemihydrate.

Maximum load sustained by a material when

subjected to a crushing force expressed as

pounds per square inch (lb./in.2) or kilograms

per square centimeter (kg/cm2).

per square centimeter (kg/cm2).

A term denoting the fluidity or viscosity of a

plaster or cementitious paste; also refers to

the amount of water required to bring a given

quantity of dry cementitious material and

aggregate to a given fluidity.

See: Expansion Joint.

A term referring to relative workability of a

plaster application resulting from water

absorption of the substrate (usually basecoat),

or of a plaster’s tendency to relinquish water

to the substrate. A cool basecoat contains

substantial free water (either freshly installed

and not dried, or rewet prior to finish

application); the finish applied to this

basecoat will be cool working, or have little

tendency to lose its water to the basecoat,

thereby maintaining sufficient water to provide

easy working and finishing characteristics.

Material used at reentrant or interior angles to

provide continuity between two intersecting

plaster surfaces.

A tool consisting of a right angle (90°) metal

form with a handle used for application of

plaster and finishing of interior angles.

A concave molding or curved surface used at

the junction between a ceiling and a wall.

Fine, random fissures or cracks of the finish

plaster surface caused by plaster shrinkage.

These are generally associated with lime

finish coat improperly gauged or troweled, or

with veneer plasters subjected to rapid-drying

job conditions.

In gypsum plastering, to provide environmental

conditions conducive to complete gypsum

hydration (low air movement and moderate

temperatures); in portland cement plastering, to

maintain sufficient quantity of water to complete

hydration.

A flat wooden or metal tool about 49 wide and

429 long with handles; used to smooth or

float the brown coat; also used on finish coat

to give a preliminary true and even surface.

429 long with handles; used to smooth or

float the brown coat; also used on finish coat

to give a preliminary true and even surface.

float the brown coat; also used on finish coat

to give a preliminary true and even surface.

float the brown coat; also used on finish coat

to give a preliminary true and even surface.

See: Anhydrous Calcium Sulfate.

The physical separation of plaster coats, or of

a plaster coat from the substrate, that results

from chemical or physical impairment of

plaster bond to previous coats or other

substrates.

The point at which air becomes saturated with

water vapor and condenses to form dew.

Types of metal lath having small diamond

pattern produced by slitting and expanding of

metal sheets. See Expanded Metal Lath.

A type of limestone containing calcium

carbonate, with up to 50% magnesium

carbonate. Also refers to the quicklime or

hydrated lime derivatives of this type of

limestone.

A term used by plasterers for additives of any

type that adjust setting, workability or bond

characteristics.

A small lump of plaster placed on a surface

(usually scarified basecoat) between grounds

to assist the plasterer in obtaining the proper

plaster thickness and aid in aligning the

surface.

Calcium magnesium hydroxide Ca (OH)2 • Mg

(OH)2, the product obtained from reaction of

water with dolomitic quicklime (CaO • MgO).

When mixed with water, forms a plastic paste

(lime putty) which may be mixed with gauging

plaster and applied as a finish plaster coat.

(OH)2, the product obtained from reaction of

water with dolomitic quicklime (CaO • MgO).

When mixed with water, forms a plastic paste

(lime putty) which may be mixed with gauging

plaster and applied as a finish plaster coat.

water with dolomitic quicklime (CaO • MgO).

When mixed with water, forms a plastic paste

(lime putty) which may be mixed with gauging

plaster and applied as a finish plaster coat.

water with dolomitic quicklime (CaO • MgO).

When mixed with water, forms a plastic paste

(lime putty) which may be mixed with gauging

plaster and applied as a finish plaster coat.

Successive plaster coat application with no

setting or drying time allowed between coats,

usually associated with veneer plastering. The

double-up coat is applied (from the same mix)

to a scratch coat over gypsum base.

A workability problem encountered during

knockdown or finish troweling, where

excessive pressure is required to draw the

trowel across the surface to smooth it. This

occurs when the material has not retained

sufficient surface moisture to lubricate the

trowel; in the extreme, the trowel may skip or

“chatter” across the surface, creating ripples.

A condition caused by excessive evaporation

or substrate water absorption, when the

plaster loses some or all of the water required

for hydration (setting). Appears as a lightcolored

soft area.

Low plasticity (hard or poor workability) of

plaster occurring substantially prior to actual

setting (hydration) reaction; see also Bucking.

A white, powdery surface deposit sometimes

found on plaster or masonry. Results from

migration of soluble salts to the surface; also

called “whiskering” or “saltpetering.”

See: Chip Cracks.

A heating system comprised of an electric

resistance heating cable attached to radiant

heat plaster base, and covered in two coats

with a specially formulated heat-resistant

plaster.

Ca2A12(SO4) • XH2O, where X = 0-30;

a dimensionally unstable material formed

when gypsum plasters or gypsum-containing

materials intimately contact portland cements

in the presence of excess moisture. As

additional moisture is made available, the

ettringite crystal (and bulk material) expands,

creating bulges, cracks, and delamination at

the portland cement/gypsum interface.

a dimensionally unstable material formed

when gypsum plasters or gypsum-containing

materials intimately contact portland cements

in the presence of excess moisture. As

additional moisture is made available, the

ettringite crystal (and bulk material) expands,

creating bulges, cracks, and delamination at

the portland cement/gypsum interface.

a dimensionally unstable material formed

when gypsum plasters or gypsum-containing

materials intimately contact portland cements

in the presence of excess moisture. As

additional moisture is made available, the

ettringite crystal (and bulk material) expands,

creating bulges, cracks, and delamination at

the portland cement/gypsum interface.

A general term to denote slit and drawn sheet

metal forming openings of various

configurations; used as a plaster base.

A product formed from sheet metal having

“W” shaped cross section; provides controlled

discontinuity at locations in a plaster

membrane to relieve stress.

Rapid stiffening (not setting) of portland

cement plaster, which can be counteracted

through additional mixing. Similar reactions

with lime and gypsum plaster are described

as bucking or early stiffening.

A mixture of fine lime and/or gypsum particles

and water accumulated on the trowel during

the finishing operation, which is used to fill in

small surface imperfections.

A metal or wood tool having a beveled edge.

Used in finish coat work to straighten

reentrant angles.

Usually a basecoat plaster containing animal

(hair), vegetable or glass fibers, which

promote cohesiveness in the mix.

The last layer of plaster applied in a multilayer

application.

Brushes used to apply water to a smooth lime

finish coat during final troweling; may be fiber

or felt type.

A term describing small blemishes (about 1⁄49

in diameter) found in lime/gauging finish

coats, caused by insufficient finish-coat

mixing.

A “photographing” or “see-through” effect

observed with plaster finishes applied over

block or tile mortar joints, plaster base joints,

and beads and trims, where nonuniform

water absorption can occur.

See: Quick Set.

A tool or procedure used to straighten and

level the finish coat, to correct surface

irregularities produced by other tools, and to

impart a distinctive surface texture.

Finish-coat texture that is rougher than a

smooth trowel finish, and which is derived

from aggregate in the mortar.

An artistic or decorative medium consisting of

a water-soluble paint applied to freshly

applied plaster.

A term applied to spacer elements (channels,

rods or strips) used to maintain a space

between a plaster application and the

structural elements behind it.

A cementitious material, such as gypsum

plaster, Keene’s cement or portland cement,

added to lime putty to provide and control set;

also the act of adding gauging material.

Glass fiber mesh material of various widths

used to reinforce joints in veneer plaster

applications over gypsum base. Attached with

stapes or pressure-sensitive adhesive.

A term to describe freshly applied plaster that

has set, but has not dried.

Piece of wood or metal attached to the plaster

base so that its exposed surface acts as a

gauge to define the thickness of plaster to be

applied. Also a term used to denote plaster

thickness.

Gypsum or portland cement plaster used to fill

crevices or to fill hollow metal door and

window frames.

A surface gypsum deposit containing loam,

clay, sand and humus impurities; gypsum

content ranges from 60% to more than 90%.

Hydrated Calcium Sulfate (CaSO4 • 2H2O);

a naturally occurring mineral that, when

calcined, serves as the base to formulate

plastering materials and other building

products.

a naturally occurring mineral that, when

calcined, serves as the base to formulate

plastering materials and other building

products.

a naturally occurring mineral that, when

calcined, serves as the base to formulate

plastering materials and other building

products.

A plaster base manufactured in sheets of

various dimensions. Composed of special

gypsum core surfaced with multilayered

absorptive face paper suitable to receive

gypsum plasters.

A cast gypsum building unit of various

dimensions for use in nonloadbearing interior

construction for protection of columns,

elevator shafts, etc., against fire.

Ground calcined gypsum combined with

various additives to achieve specific

application, working and set characteristics.

A term referring to a method of application of

plastering materials using a hawk and trowel.

A generic term referring to conventional gypsum

basecoat plaster.

A tool used by plasterers to hold and carry

plaster; consists of a flat wood or metal piece

from 109 to 149 square, with a wooden

handle centered and attached to the

underside.

handle centered and attached to the

underside.

handle centered and attached to the

underside.

CASO4 • 1/2 2H2O; a calcined gypsum used

for plaster formulation.

for plaster formulation.

for plaster formulation.

A type of lime containing mainly calcium oxide

or hydroxide and not more than 5%

magnesium oxide or hydroxide.

A term describing the ease with which a

plaster may be handled with a hod or hawk;

depends on plaster flow characteristics and

angle of repose.

The water retention characteristic or property

of a plaster.

Opposite of cool; refers to plaster working

characteristics, where reduced spread and

plasticity result from excessive basecoat

absorption of available water from the plaster,

or plaster has an increased tendency to

relinquish available water to the basecoat.

To chemically combine water as in the

hydration of calcined gypsum: CaSo4 •

1/2H2O + 3/2H2O Õ CaSO4 • 2H2O, or

slaking of quicklime: CaO + H2O Õ Ca (OH)2.

Also the product resulting from this

combination.

1/2H2O + 3/2H2O Õ CaSO4 • 2H2O, or

slaking of quicklime: CaO + H2O Õ Ca (OH)2.

Also the product resulting from this

combination.

slaking of quicklime: CaO + H2O Õ Ca (OH)2.

Also the product resulting from this

combination.

Also the product resulting from this

combination.

Also the product resulting from this

combination.

Ca (OH)2 or Ca (OH)2 • MgO; produced by

slaking, or adding water to, calcium quicklime

(CaO) or dolomitic quicklime (CaO • MgO).

slaking, or adding water to, calcium quicklime

(CaO) or dolomitic quicklime (CaO • MgO).

slaking, or adding water to, calcium quicklime

(CaO) or dolomitic quicklime (CaO • MgO).

The dimensional response (expansion or

contraction) of gypsum laths and set

cementitious materials due to a variation in

relative humidity.

See: Retarder.

The junction of two masonry, gypsum lath or

other plastering bases, in a plane surface.

Deviation of the formed joint from a plane

surface; may be referred to as “ridging,”

“beading,” “lipping” or “stepping” of the joint.

Condition may be caused by improper lath

attachment; improper joint treatment to

achieve reinforcement; irregular water

absorption over the joint; abnormal substrate

movement in response to thermal,

hygrometric (humidity), structural and other

construction influences.

A plasterer or lather who, through training

and experience, has become thoroughly

skilled in the trade.

An anhydrous gypsum plaster of low

consistency that, when mixed with lime putty,

provides a dense, hard finished surface. This

material is unique in that it may be

retempered using water and reworked with a

trowel to resume the plastic, workable state.

An intermediate plaster finishing step where

sizable surface imperfections of the partially

stiffened plaster application are removed prior

to final finish troweling.

Coarse-ground natural gypsum that is

calcined for the manufacture of gypsum

plasters.

Dry powder or emulsified admixtures that

improve plaster plasticity, surface hardness

and compressive strength of the set material,

and that improve bond between the plaster

and base.

A metal or gypsum material applied

separately to a structure that serves as a base

for plaster.

Any plaster which has a high ratio of

aggregate to cementitious material. Usually

exhibits poor or hard working characteristics.

Low-density, inert aggregates such as

vermiculite and perlite (as opposed to silica

sand and pumice).

The principal product derived from calcining

various types of limestone consisting of

oxides or hydroxides of calcium or

magnesium.

A basecoat plaster consisting of lime and

aggregate.

A finishing material resulting from slaking of

quicklime or soaking and mixing hydrated

lime with water to form a plastic mass;

usually mixed with a gauging plaster or

gauging and aggregate as a finish over

basecoat.

Plaster application by mechanical means;

generally by pumping and spraying.

See: Type “N” Hydrated Lime.

The physical kerfing of one plaster coat to

another, or to a plaster base; e.g., clinching

of plaster keys to expanded metal lath, and

the bond obtained between adjacent plaster

coats by brooming or crossraking the first

coat prior to set.

A metallic plaster base manufactured from

sheet metal by slitting and expanding, or by

punching and forming.

A plastic mixture composed of water and a

cementitious material, which may be machine

or hand applied, and which hardens in place.

A basecoat gypsum plaster product produced

and supplied without aggregate. It is intended

to be job mixed with aggregate, such as sand,

perlite or vermiculite.

A fine-grind, high-consistency hemihydrate

gypsum that, when mixed with water, yields a

pourable slurry for casting ornamental trim

units or decorative plaster runwork.

Veneer plastering; the veneer finish is applied

to veneer gypsum base or other approved

substrate in a scratch and double-up method

(both “coats” from the same batch), to a full

thickness of 1/169 (1.6 mm) to 3/329

(2.4 mm).

The amount of time, from the point of mixing,

during which a plaster retains a plastic

workable consistency, until it becomes too

stiff to be applied.

To coat with plaster; usually refers to

application to foundation walls and rough

masonry.

Mild steel rods of 3/169 (4.8 mm), 1/49

(6.4 mm), or 3/89 (9.5 mm) diameter, used to

provide rigid internal reinforcement of the

base for plaster application.

provide rigid internal reinforcement of the

base for plaster application.

provide rigid internal reinforcement of the

base for plaster application.

A siliceous volcanic glass that, when

expanded by heat, is used as a lightweight

plaster aggregate.

A cementitious material or combination of

cementitious materials and aggregate that,

when mixed with water, forms a plastic mass.

When applied to a surface, plaster adheres to

it and subsequently sets or hardens,

preserving in a rigid state the form or texture

imposed during the period of plasticity.

CaSO4 • 1/2H2O or hemihydrate gypsum

without set control additives, used in casting

and industrial applications.

without set control additives, used in casting

and industrial applications.

without set control additives, used in casting

and industrial applications.

The property of plaster that permits

continuous and permanent deformation in any

direction. As opposed to fluidity, a plastic

material requires a measurable force (yield

value) to initiate flow. A material of low

plasticity is usually described as being “poor”

or hard working; high plasticity is described

as “rich” or easy working.

An admixture to improve plasticity,

workability, and spread under the trowel.

See: Chip Cracks. Usually refers to gauged

lime putty finish where the unhydrated

magnesium oxide (MgO) in the hydrated lime

hydrates over a long period of time when

exposed to free moisture. Results in local

areas of high expansion in the finish surface

that may crack and “pop” off, leaving small

craters or blemishes in the surface.

A cementitious material made by heating a

mixture of limestone and clay containing

oxides of calcium, aluminum, iron and silicon

in a kiln, and pulverizing the resultant clinker.

This material is usually mixed with lime and

aggregate for exterior plastering (stucco

work), or in interior construction in areas

where high resistance to moisture is required.

Alum; a generally recognized accelerator of

gypsum plaster. Usually spray applied as a

solution to dry basecoat plaster or faded

veneer gypsum base to promote bond of

subsequent layers of plaster.

An open-weave, glass-fiber joint

reinforcement tape used in veneer finishing,

coated with a pressure-sensitive adhesive for

easy application to base without need for

staple attachment.

A smooth-troweled finish plaster coat

containing lime putty and a gauging plaster.

CaO or CaO • MgO; materials produced by

burning or calcining limestone. For plastering,

quicklime is slaked with water to hydrate the

material to form Ca(OH)2 or Ca(OH)2 • MgO.

The resulting lime putty is gauged for use as

a finish coat.

The resulting lime putty is gauged for use as

a finish coat.

The resulting lime putty is gauged for use as

a finish coat.

Premature hardening (setting) of a plaster.

This condition may be attributed to improper

job use of accelerator, damp plaster prior to

mixing, contamination of the mix (rusty or

dirty mixing water, equipment or tools), or

other factors.

A plastering tool with tines (teeth) that is used

to roughen or scarify basecoat plaster

application prior to set. Promotes mechanical

bond with the finish-coat plaster layer.

Job environmental conditions that cause

premature removal of water from the plaster

(prior to set), which results in incomplete

hydration of the gypsum plaster; e.g., high

temperature, low relative humidity and high

air movement. These conditions promote dryout

and a variety of shrinkage cracking

problems as a result of rapid and excessive

evaporation.

Gypsum neat plaster “Type R”; calcined

hemihydrate gypsum mill-mixed with

materials to control set and working

properties; sand aggregated on the job for

application over gypsum lath to a maximum

thickness of 1/49 (6.4 mm).

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.

An admixture used to delay the setting action

of plasters or other cementitious materials.

A procedure whereby plaster (usually Keenes

cement or portland cement) is remixed to a

workable consistency using water and/or

mechanical action.

See: Plasticity.

See: Joint Deformation.

A straightedge tool of various lengths used to

straighten the surface of wall and ceiling

plaster applications.

A plaster installation where the material is

applied in a continuous formed method

using a metal or wood template; usually

done as a decorative application at

wall/ceiling junctions.

A warping condition in ceiling construction

where the lath and plaster bow down from the

framing members; can result from a variety of

causes, such as improper framing, spacing,

long-setting plaster, slow drying conditions,

excessive weight of insulation, and improper

placement of vapor barrier.

A portable gas or oil-burning heater used at a

jobsite to provide minimum comfortable

working conditions and prevent freezing of

plaster.

Loose granular aggregate resulting from

natural disintegration of siliceous rock or from

crushing of friable sandstone; serves as an

inert filler and provides internal expansion and

contraction stress relief in plaster mix,

minimizing cracking problems.

See: Scratch Coat.

1. A method of texturing a sanded finish coat

that raises sand particles to the plaster

surface through use of a dampened

sponge or sponge rubber float.

2. Refers to the type of finish texture

obtained through use of a sponge or

sponge rubber float.

A temporary platform or network of support

members erected at a jobsite to permit safe

and convenient construction, repair or

cleaning of a structure.

See: Rake.

Noun, See: Grounds; Verb, to level or

straighten a plaster coat application with a

rod, darby or other similar tool (e.g., a

“screed” bar).

Woven natural or artificial fiber material

coated with a binder or binder and adhesive;

used to provide joint reinforcement.

The elapsed time required for a cementitious

material to attain a specified hardness after

mixing with water. The set time is a physical

indicator for the chemical reaction of

hydration in gypsum plasters.

Metal lath formed by punching perforations in

steel sheets; made from heavier gauge steel

than expanded metal lath; has greater

stiffness.

See: Storage Life.

See: Sand.

See: Hydrated Lime.

A thin finish plaster coat troweled smooth.

See: Hydrated Lime.

A beveled device four feet (1.2 m) long and 69

to 89 (15.2-20.3 mm) wide, sometimes used

by a plasterer in place of a darby to level and

smooth a plaster coat.

by a plasterer in place of a darby to level and

smooth a plaster coat.

by a plasterer in place of a darby to level and

smooth a plaster coat.

A plaster workability characteristic relating to

the relative ease with which the trowel is

drawn over the plaster surface both during

application and after the coat has stiffened or

“taken up.”

See: Chip Cracking.

A term referring to the extendibility or

coverage obtained with a plaster; sometimes

used incorrectly to refer to plaster workability.

Fiber-reinforced ornamental plaster casts.

Devices employed by plasterers which are

strapped to the feet, providing an elevated

footrest to permit ceiling and high wall

application without use of cumbersome

scaffolding. Stilts have extension capability of

up to three feet (0.91 m).

The time during which packaged material can

be stored under specified temperature and

humidity conditions and remain suitable for

use.

1. A cementitious material used in exposed

exterior building construction.

2. A plaster manufacturing term referring to

freshly calcined gypsum not yet formulated

or processed into a finished plaster product.

The absorptive quality of a surface, such as

concrete masonry, gypsum lath, previous

plaster coat, etc., which is to be plastered.

A defective gypsum plaster condition

characterized by a soft, damp area remaining

after the surrounding area has set. This is

usually caused by insufficient ventilation,

which inhibits normal drying.

The loss of water of a plaster into the

absorptive substrate during application, as

evidenced by a moderate stiffening of the

plaster coat.

A gauge or pattern used as a guide to

produce arches, curves and other shapes or

forms of a repetitive nature (see: Runwork).

A patterned plaster finish as contrasted to a

smooth finish.

A stress created by an extreme or sudden

change in temperature that may result in

cracking of plaster after application.

See: Rapid Plaster or Veneer Plaster.

The property of a plastic mass that enables

the material to achieve higher fluidity on

agitation, and to thicken on subsequent rest.

The application of plaster in three successive

coats—scratch, brown, finish—leaving time

between coats for setting and/or drying of the

plaster.

Soft annealed steel wire used to joint lath

supports, attach metal lath to supports, and

reinforce metal lath joints.

A natural, well graded plastering sand

obtained from pits along the Fox River, west

of Chicago, Illinois.

A tool used by a plasterer to apply, spread,

shape and smooth plaster.

See: Blistering.

See: Double-Up.

A veneer plaster installation consisting of a

veneer basecoat and finish coat. Each coat is

applied using the scratch and double-up

method, with the basecoat allowed to set

prior to finish coat application. Each coat is

applied to a nominal 1/169 (1.6 mm)

thickness, for a total installation thickness of

1/169 (3.2 mm) to 3/169 (4.8 mm).

thickness, for a total installation thickness of

1/169 (3.2 mm) to 3/169 (4.8 mm).

See: Type “S” Hydrated Lime.

See: Rapid Plaster.

A special hydrated finishing lime, distinguished

from type “N” (normal or mason’s hydrated

finishing lime) by restrictions on the amount of

unhydrated oxides.

A gypsum lath with specially formulated core

to increase fire retardent properties and

improve system fire-resistance rating.

UV light; the component of sunlight that can

degrade gypsum-lath face paper to produce

organic acids. These acids react with an

alkaline veneer plaster, forming a potent

retarder at the plaster/gypsum base interface,

and destroying the mechanical bond of the

plaster to the gypsum base.

See: Basecoat.

A term referring to the condition of a plaster

installation whereby the hardened mass has

lost internal strength, exhibiting cracking,

spalling, delamination, etc. This general state

may be contributed to by excessive aggregate

addition, water damage, poor drying

conditions, overwatering and other factors.

A special lath four feet (1.22 m) wide and in

various lengths, having blue-tinted face

paper; used as a plaster base for one- and

two-coat veneer plaster application.

A calcined gypsum plaster specially

formulated to provide specific workability,

strength, hardness and abrasion-resistance

characteristics when applied in thin coats

(1/169 nominal) over veneer gypsum base or

other approved base. The term thin-coat

plaster is sometimes used in reference to

veneer plaster.

other approved base. The term thin-coat

plaster is sometimes used in reference to

veneer plaster.

other approved base. The term thin-coat

plaster is sometimes used in reference to

veneer plaster.

See: Aggregate. A micaceous mineral

expanded by heat and used as a lightweight

plastering aggregate.

See: Combined Water.

A plaster condition indicative of a poor waterretention

characteristic. When at rest on a

mortar board, the plaster loses or “weeps”

free water in puddles or depressions in the

mass.

The ability or characteristic of a plaster to

retain sufficient water, when applied to an

absorptive surface, to maintain a plastic

workable state under the trowel for ease of

application.

See: Water-Out.

A gauged lime putty finish plaster or, more

generally, any white finish plaster coat.

See: Aggregate.

A mill-prepared gypsum plaster formulated

with shredded or ground-wood fiber; usually

used as a scratch coat over expanded metal

lath.

A general term encompassing the

performance of a plaster mortar under the

trowel in terms of spread, plasticity and slip.

See: Open Time.

A gypsum plaster specially formulated for use

in construction wherever x-ray equipment is used.