Acoustic plaster – a porous sound absorbing plaster.

Admixture – Any ingredient added to the plaster mix other than the basic three ingredients (i.e. water, aggregate and binder).

Aggregate – A granular material used in mixes and to add texture. Examples are sand, crushed marble, granite, quartz, perlite, and vermiculite.

Angle plane – A hand tool with cross blades used for preparing a set brown coat for the finish coat by knocking down high spots.

Base coat – All plaster coats applied prior to the application of the finished coat.

Bead – Edging trim such as cornerbead, stopbead and casing bead.

Blistering – Bubbles in the finish coat where it separates from the base coat. Similar to blisters you get on your feet.

Bond – Adhesion of plaster to other surfaces.

Bonding agent – A material used as an admixture or applied as a coating to a substrate to enhance bonding of the subsequent layer. It has been none also as “paint on lath”.

Brown coat – The second coat of a three coat plaster application. It is the coat of plaster applied over the scratch coat to straighten and allow a good surface for the final textured finish coat.

Brown out – “To complete” an application of a brown coat.

Browning brush – A brush used to throw water on the surface of the plaster to provide a slippery surface and provide ease in straightening the surface of the plaster. It is also used to wash plastering tools.

Casting plaster – A very fine plaster used in molds for art and statues.

Checking – Fine, random, shallow and irregular cracks in the plaster surface.

Control joint – A break in the plaster or stucco to allow for expansion or contraction of the material to reduce cracking. Also known as expansion joint.

Corner reinforcement – Metal trim used for reinforcement at corners between two plaster walls.

Corner trowel – There are inside and outside corner trowels and each is used to finish corners as the name implies.

Cornice – A horizontal molding projecting along the top of a wall or building.

Curing – A period of time following application when the plaster is wet (or kept wet) to allow proper hardening.

Darby – An instrument made for leveling base coat plaster. It has one serrated edge that is used on base plaster for bonding.

Dash brush – A texture brush used for dipping into the finish material and throwing it on the surface.

Dash texture – A finish coat of thick plaster that is applied with a Dash brush by hand splattering.

Discoloration – A change in the color of the plaster from the normal or desired.

Double-back – An application of a second coat of plaster to the scratch coat as soon as the scratch coat has become sufficiently rigid to receive it.

Efflorescence – A white substance that can form on the surface of plaster during evaporation.

Expanded metal lath – Sheets of metal lath that have diamond shaped openings and are used as reinforcement for plaster.

Expansion joint – A break in the plaster or stucco to allow for expansion or contraction of the material to reduce cracking. Also known as a control joint.

Exposed aggregate – In stucco finishes, it is the stones or pebbles embedded and seen in the finished texture.

Featheredge – A long straight and sturdy tool used for evening a plaster finish and straightening corners.

Finish coat – The final coat of plaster which is usually colored and textured to provide a decorative finish.

Finishing brush – A felt or bristle brush of high quality used to apply water to the plaster surface and prevent the surface from being scratched.

Float – A tool similar to a trowel, but with a pad added. The pad material can be foam, cork, rubber or even carpet. It is basically used to level off humps and fill in hollows.

Gauge (Gage) – In plastering, to mix the right proportions, depending on the required drying time.

Gauging plaster – Special plaster designed to set at definite time intervals.

Gypsum – Also known as calcium sulphate. It is a common substance used in plastering and found naturally in the environment.

Hairline cracks – Very fine cracks that have basically a straight line pattern.

Hawk – An instrument used to hold plaster mud needed for immediate use during hand application. It is used in conjunction with a trowel which picks up the mud from the hawk.

Hod – A tool which has a bucket-like container attached to a long handle that allows the hod-carrier to balance the bucket with mud on this shoulder and enable him to carry mud up scaffolding.

Hod carrier – A helper to a journeyman plasterer. He usually does a lot of the mixing and hard labor such as hauling the mud to where the plasterer is working. The name is derived from a tool called a hod.

Hydrocal – A special molding plaster that is stronger and harder than molding plaster.

Hydrostone – An extremely strong casting plaster used for industrial applications.

Keenes cement – A high strength white plaster with slaked lime that can be remixed if the material starts to set.

Lath – The applied base over which coats of plaster are applied. Lath has developed over the years and today is mostly applied over metal lath or gypsum boards, but in the past has also been applied over other materials such as reeds and wood.

Lathing hatchet – Also known as a lathing axe. A tool used by plasterers to cut and nail lath. It has a thin, sharp, long blade on one end and a hammering edge with grooves on the other end.

Lime – Lime for plastering is from limestone which is a natural rock made up mostly of calcium carbonate.

Lime mortar – This type of mortar is the oldest used by plasterers. It is still used today under certain conditions, but has mostly been replaced by Gypsum mortar. The basic mixture is lime and sand with enough water added to make a workable mixture.

Lime putty – A slacked lime that is strained for lumps and let set to form a smooth paste.

Marble dust – Marble which is ground up finely and used as an aggregate in a plaster mix.

Marblecrete – A type of exposed aggregate finish where the exposed aggregate is pieces of marble which are embedded in the stucco finish.

Margin trowel –A small hand tool with a square tip that is used where a larger trowel will not fit and also used to clean tools similar to the pointing trowel. Plasterers often put a notch in the sides of this trowel to aid in trimming the base coat along corner bead.

Mechanical bond – The adhesion of one plaster coat to another or to a substrate created by irregularities such as those made with a scratcher.

Metal lath – A variety of metal backing for plaster that includes wire mesh, expanded metal lath, expanded rib lath, wire lath and sheet lath.

Midget trowel – Similar to a regular plasterers trowel but smaller. They are used for window sills, closets and small areas.

Mineral pigments – Also known as natural pigments. Color pigments derived from minerals mined directly from the earth.

Miter rod – Pieces of metal used to shape joints and miters in cornice work and for sharpening of inside angles.

Molding plaster – A fine plaster used in molds for trim, cornices and cast work.

Mortar mixer – A large drum- like machine with rotating paddles used to mix larger amounts of plaster mortar thoroughly and in a short period of time.

Muriatic acid – An acid that is mixed with water and used to wash concrete surfaces in preparation for plaster.

Ornamental plaster – Artistic additions to plaster including but not limited to molded or casted plaster pieces, cornices, and columns etc.

Pipe trowel – Similar to the regular plasterers trowel but has a longer thiner blade for reaching behind fixtures and pipes.

Pointing trowel – A small hand tool, with a pointed end, that is used where a larger trowel will not fit and also used to clean tools.

Pool trowel – A hand trowel like a regular plasterers trowel but with rounded edges.

Portland cement – Invented in 1824 to be a mortar that would harden under water. It is basically a mixture of lime and clay. Although there are different types of cement products, regular Portland cement is the most common and widely used by plasterers today.

Putty coat – A common plaster finish, also known as hard coat, cream coat, or smooth coat. It can be worked to a smooth surface and is easily repairable.

Retempering – After initial mixing, adding water and remixing plaster that has started to stiffen.

Rod – Also known as a straight-edge. It is a tool used to straighten the face of walls and ceilings by cutting off excess plaster to establish a flat plane.

Scarifier – Also known as a scratcher. It is a tool with flexible steel tines used to scratch the surface of an undercoat to allow the succeeding coat to have sufficient bond.

Scoring – The act of making grooves in the scratch coat with a scratcher or scarifier to enable bonding of the subsequent coat.

Scratch coat – The first coat of plaster applied to a surface (usually lath) in a two or three coat application.

Scratcher – Also known as a scarifier. It is a tool with flexible steel tines used to scratch the surface of an undercoat to allow the succeeding coat to have sufficient bond.

Screed – A strip or trim placed at intervals along a wall to be plastered, to gauge the thickness of the plastering.

Self-furring – Metal or wire lath that has raised areas that hold the lath away from the surface and allow good bonding for the plaster.

Set – The change in plaster from a workable state to a solid rigid or unworkable state.

Silica sand – Is a special white sand that comes in various sizes and is used for textured finishes and some veneer plaster bases.

Slaked lime – A process whereby water is added to baked quick lime, then strained, and aged for at least six months. Slaked lime is used in Venetian plaster.

Stilts – Used by plasterers in place of low scaffolding to reach high places (usually ceilings).

Structo-gauge – A gauging plaster that is also an extremely high strength finishing plaster.

Suction – The absorptive capacity of a surface.

Thickness of plaster – Plaster thickness is measured from the lath backing (metal, wood etc.) to the specified plaster surface (i.e. scratch, brown or finish).

Tin snips – A tool used by plasterers to cut metal lath, corner bead and other trim pieces.

Trowel – A flat steel hand tool and one of the main tools used by plasterers to apply spread and shape and smooth plaster materials.

Veneer plaster – A plaster designed for a one or two coat application (i.e. designed to eliminate or reduce the brown coat). It is also known as rapid or thin coat plaster.

Vermiculite – A natural ore that resembles mica and is used in plaster for its acoustic, insulating and fireproofing properties.