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Sealants Glossary

Browse Atlas Supply’s Sealants Glossary below for the definitions of building construction sealant terms. Visit Sealants & Adhesives afterwards, for product descriptions from building construction sealant manufacturers ranging from 3M™ and DOWSIL™ to Sika and Master® Builders Solutions MasterSeal® (formerly Sonneborn).

Accelerated Aging
A set of laboratory conditions designed to produce in a short time the results of normal aging. Usual factors included are temperature, light, oxygen, and water.
The clinging or sticking together of two surfaces. The state in which two surfaces are held together by forces at the interface.
Adhesion, Mechanical
Adhesion due to the physical interlocking of the adhesive with the surface irregularities of the substrate.
Adhesion Failure
Type of failure characterized by pulling the adhesive or sealant loose from the adherend.
The progressive change in the chemical and physical properties of a sealant or adhesive.
Cracking of a surface into segments so that it resembles the hide of an alligator.
A compressible material used at the base of a joint opening to provide the proper shape factor in a sealant.
A sealant or compound after application in a joint irrespective of the method of application, such as caulking bead, glazing bead, etc. Also a molding or stop used to hold glass or panels in position.
Bed or Bedding
The bead of compound applied between light of glass or panel and the stationary stop or sight bar of the sash or frame, and usually the first bead of compound to be applied when setting glass or panels.
Amount of overlap between the stop and the panel or light.
Bock (Setting)
A small piece of neoprene or other suitable material used to position the glass in the frame.
The attachment at an interface between substrate and adhesive, or sealant.
Bond Breaker
Thin layer of material (e.g., bond breaker tape) used to prevent the sealant from bonding to the bottom of the joint.
Bond Strength
The force per unit area necessary to rupture a bond.
Butt Joint
A joint in which the structural units are joined to place the adhesive or sealant into tension or compression.
Application of putty or sealant compound to the flat surface of some member before placing the member in position, such as the buttering of a removable stop before fastening the stop in place.
Butyl Rubber
A copolymer of isobutene and isoprene. As a sealant it has low recovery and slow cure, but good tensile strength and elongation.
Substance added in small quantities to promote a reaction, while remaining unchanged itself.
Caulk (noun)
A sealant with a relatively low (less than 20%) movement capability.
Caulk (verb)
To fill the joints in a building with a sealant.
Formation of a powdery surface due to weathering.
A three-sided, U-shaped opening in sash or frame to receive light or panel, as with sash or frame units in which the light or panel is retained by a removable stop. Contrasted to a rabbet, which is a two-sided L-shaped opening, as with face glazed window sash.
Channel Depth
The measurement from the bottom of the channel to the top of the stop, or measurement from sight line to base of channel.
Channel Glazing
The sealing of the joints around lights or panels set in a U-shaped channel employing removable stops.
Channel Width
The measurement between stationary and removable stops in a U-shaped channel at its widest point.
The formation of slight breaks or cracks in the surface of a sealant.
Chemical Cure
Curing by chemical reaction. Usually involves the crosslinking of a polymer.
Wire spring devices to hold glass in rabbeted sash, without stops, and face glazed.
Coefficient of Expansion
The coefficient of linear expansion is the ratio of the change in length per degree to the length at 0°C.
The molecular attraction which holds the body of a sealant or adhesive together. The internal strength of an adhesive or sealant.
Cohesive Failure
The failure characterized by pulling the body of the sealant or adhesive apart.
Compressible Tape
A preformed sealant which is installed then compressed and held in compression.
Pressure exerted on a compound in a joint, as by placing a light or panel in place against bedding, or placing a stop in position against a bead of compound.
Compression Set
The amount of permanent set that remains in a specimen after removal of a compressive load.
A series of fine cracks which may extend through the body of a layer of sealant or adhesive.
The deformation of a body with time under constant load.
Molecules that are joined side by side as well as end to end.
To set up or harden by means of a chemical reaction.
Cure Time
Time required to effect a complete cure at a given temperature.
Curing Agent
A chemical which is added to effect a cure in a polymer.
Curtain Wall
Any building wall, of any material, which carries no superimposed vertical loads. (i.e., any non-bearing wall)
The ability of a material to return to its original shape after removal of a load.
A rubbery material which returns to approximately its original dimensions in a short time after a relatively large amount of deformation.
An organic material used to increase the volume and lower the cost of a sealant or adhesive.
The ability of a sealant to stretch under tensile load.
Exterior Glazed
Glass set from the exterior of the building.
Exterior Stop
The removable molding or bead that holds the light or panel in place when it is on the exterior side of the light or panel, as contrasted to an interior stop located on the interior side of the light.
Extrusion Failure
Failure which occurs when a sealant is forced too far out of the joint. The sealant may be abraded by dirt or folded over by traffic.
Face Glazing
On rabbeted sash without stops, the triangular bead of compound applied with a glazing knife after bedding, setting, and clipping the light in place.
Fatigue Failure
Failure of a material due to rapid cyclic deformation.
Finely ground material added to a sealant or adhesive to change or improve certain properties.
Strips, usually of sheet metal, to waterproof the junctions of building surfaces, such as roof peaks and valley, and the junction of a roof and chimney.
Pre-formed shapes, such as strips, grommets, etc., of rubber or rubberlike composition, used to fill and seal a joint or opening either alone or in conjunction with a supplemental application of a sealant.
The top member of a window or door frame.
Heel Bead
Compound applied at the base of channel, after setting light or panel and before the removable stop is installed, one of its purposes being to prevent leakage past the stop.
Hot Melt
As a sealant it is material which will soften when heated (approx. 375°F) can be pumped when hot, gains strength when cooled.
Interior Glazed
Glass set from the interior of the building.
Interior Stop
The removable molding or bead that holds the light in place, when it is on the interior side of the light, as contrasted to an exterior stop which is located on the exterior side of a light or panel.
The side of a window, door opening, or frame.
Joint (adhesive use)
The opening between component parts of a structure.
Lap Joint
A joint in which the component parts overlap so that the sealant or adhesive is placed into shear action.
Latex Caulks
A rubbery emulsion caulking material. The most common latex caulks are polyvinyl acetate or vinyl acrylic.
Light (Lite)
Another term for a pane of glass used in a window.
Mastic (broad interpretation)
Any field molded sealant or adhesive. Includes materials which are gunned, poured, or troweled into place.
The ratio of stress to strain.
A material composed of single molecules. A building block in the manufacture of polymers.
External structural member in curtain wall building. Usually vertical. May be placed between two opaque panels, between two window frames, or between a panel and a window frame.
Descriptive of a compound that does not form a surface skin after application.
Open Time
Time interval between when an adhesive is applied and when it becomes no longer workable.
Formation of an oxide. Also the deterioration of rubbery materials due to the action of oxygen or ozone.
A reactive form of oxygen. A powerful oxidizing agent, it occurs naturally in the atmosphere.
Peel Test
A test of an adhesive or sealant using one rigid and one flexible substrate. The flexible material is folded back (usually 180°) and the substrates are peeled apart. Strength is measured in pounds per inch of width.
Permanent Set
The amount of deformation which remains in a sealant or adhesive after removal of a load.
A material which softens a sealant or adhesive by solvent action.
The cgs unit of viscosity. Example: A polysulfide highway joint sealant might have a viscosity of 500 poises, at 77°F. Higher numbers indicate a more viscous material.
A compound consisting of long chain-like molecules. The building units in the chain are monomers.
Polysulfide Rubber
Synthetic polymer usually obtained from sodium polysulfide. The polymer segments are generally terminated with -SH groups. Polysulfide rubbers make very good sealants.
Preformed Sealant
A sealant which is preshaped by the manufacture before being shipped to the job site.
Pressure Sensitive Adhesive
Adhesive which retains tack after release of the solvent, so that it can be bonded by simple hand pressure.
A preparatory material which is applied to joint faces in order to improve adhesion.
A two-sided L-shaped recess in sash or frame to receive lights or panels. When no stop or molding is added, such rabbets are face glazed. Addition of a removable stop produces a three-sided U-shaped channel.
The framed opening ready to receive a pre-glazed sash or panel.
Reinforcement (in rubbers)
Increase of modulus, toughness, tensile strength, and so forth, by the addition of selected fillers.
A measure of energy stored and recovered during a loading cycle. It is expressed in percent.
Solid organic materials, generally not soluble in water, which have little or no tendency to crystallize. Example: Epoxy and polyester resins.
The frame including muntin bars when used, and including the rabbets to receive lights of glass, either with or without removable stops, and designed either for face glazing or channel glazing.
Any material used to seal joints or openings against the intrusion or passage of any foreign substance such as water, gases, air, or dirt.
A surface coating generally applied to fill cracks, pores, or voids in the surface.
Self-Leveling Sealant
A sealant which is fluid enough to be poured into horizontal joints. It forms a smooth, level surface without tooling.
Screw-on Bead or Stop
Stop, molding or bead fastened by machine screws as compared with those that snap into position without additional fastening.
Shear Test
A method of deforming a sealed or bonded joint by forcing the substrates to slide over each other.
Strength is reported in units or force per unit area (psi).
Shelf Life
The length of time a sealant or adhesive can be stored and still retain its properties.
Shore Hardness
Measure of firmness of a compound by means of a Durometer Hardness Gauge (Range of 20-25 is about the firmness of an art gum eraser. (Range of 90 is about the firmness of a rubber heel.).
Percentage weight loss under specified conditions.
Silicone Rubber
A synthetic rubber based on silicone, carbon, oxygen and hydrogen. Silicone rubbers are widely used as sealants and coatings.
Sight Line
Imaginary line around the perimeter of a glazed glass product defined by the top edge of stationary and removable stops, or the line where the glazing sealant or gasket contacts the glass.
Liquid in which another substance can be dissolved.
Spacers, Flat
Small blocks of composition, neoprene, etc., placed on each side of lights or panels to center them in the channel and maintain uniform width of sealant beads. Prevent excessive sealant distortion.
Spacer Shims “L” Shape
Devices that are “L” shaped in cross section and an inch or more in length, placed on the edges of lights or panels to serve both as shims to keep the lights or panels centered in the sash or frames, and as spacers to keep the lights or panels centered in the sash or frames, and as spacers to keep the lights or panels centered in the channels and maintain uniform width of sealant beads.
The panel on a curtain wall which covers the area between floors.
Spandrel Lite
Same as spandrel except made of opaque glass.
Stationary Stop
The permanent stop or lip of a rabbet on the side away from the side on which lights or panels are set.
Either the stationary lip at the back of a rabbet, or the removable molding at the front of the rabbet, either or both serving to hold light or panel in sash or frame, with the help of spacers.
An adherend. The surface to which a sealant or adhesive is bonded.
The stickiness of the surface of a sealant or adhesive.
Tear Strength
The load required to tear apart a sealant specimen. ASTM test method D-624 expresses tear strength in pounds.
Tensile Strength
Resistance of a material to a tensile force (a stretch). The cohesive strength of a material, expressed in psi.
A material which can be repeatedly softened by heating. Thermoplastics generally have little or no chemical crosslinking.
A material which hardens by chemical reaction. Not remeltable. The reaction usually gives off heat.
Nonsagging. A material which maintains its shape unless agitated. A thixotropic sealant can be placed in a joint in a vertical wall and will maintain its shape without sagging during the curing process.
Poisonous or dangerous to humans by swallowing, inhalation, or contact resulting in eye or skin irritation.
Ultimate Elongation
Elongation at failure.
Ultraviolet Light
Part of the light spectrum. Ultraviolet rays can cause chemical changes in rubbery materials.
Term normally used to refer to one single light of insulation glass.
United Inches
Total of one width and one height in inches.
A family of polymers ranging from rubbery to brittle. Usually formed by the reaction of a disocyanate with a hydroxyl; also called polyurethane.
Vinyl Glazing
Holding glass in place with extruded vinyl channel or roll-in type.
A measure of the flow properties of a liquid or paste. Example: Honey is more viscous than water. Water (the standard of comparison) has a viscosity of 1/100 of a poise.
Improving the elastic properties of a rubber by a chemical change.
An environmental chamber in which specimens are subjected to water spray and ultraviolet light.