S

Sagging (extended definition)
Coating defect: unsightly gravity-driven flow of a paint film applied on vertical surfaces. Caused by to too much flow, often related to application technique or environment. Sagging can be prevented by rendering the paint pseudo-plastic, but this may deteriorate the leveling.

Salt atmosphere
Moist, heavily laden air with a high chloride concentration. Used as a test for accelerated corrosion evaluation.

Sandability
Ease of sanding of a coating.

Satin finish
Appearance of paints having a 60?gloss reading between 10 and 40.

Scratch resistance
Ability of a coating surface to resist to damage caused by sharp and hard objects. Influenced by the hardness, the coefficient of friction and the thickness of the film.

Scrub resistance
Ability of a coating surface to resist to damage caused by rough objects in the presence of an active medium (water or organic liquid, abrasive material).

Sealer
Coating used on absorbent surfaces prior to a finish coat.

Secondary drier
Additive used in combinations with a primary drier to accelerate the drying of a coating film. Syn. Auxiliary driers.

Sedimentation
Coating defect: pigment and extender particles sinking to the bottom of the paint, caused by gravity. The velocity of sedimentation increases with particle size and the difference in the density between the particle and the medium liquid.

Seeding
Coating defect: formation of small agglomerates or gel particles (seeds) in a coating. Caused by resin insolubility, aggregation of pigment particles, or a combination of both factors.

Separation
Formation of two or more phases in paints when stored or heated. Can be caused by loss of compatibility between polymer components or by pigment separation.

Settling
Coating defect: formation of hard sediments on the bottom of the coating can due to aggregate instability of a pigment, extender or other solid suspension.

Shade
Particular hue or tone of the paint.

Shelf Life
Period of time during which a paint stored according to the manufacturer's instructions (packaging, temperature, humidity) retains its expected properties.
Syn. Pot life

Siccative
Catalyst used for drying according to the oxidative polymerization mechanism.
Syn. Drier

Side effect
Negative effect caused by interaction between an additive and an other component of the coating formulation. Can induce coating defects.

Silicone
Polymeric product possessing a molecular backbone made up of alternating silicon and oxygen atoms and which has pendant hydrocarbon groups attached to the silicon atoms. Offers excellent resistance to water and large variations in temperature (-100°F to +600°F).

Silking
Coating defect: fine parallel irregularities in a paint film that give the appearance of silk. This defect usually is a special case of floating and flocculation in coating finishes.

Skinning
Formation of a thin, tough film on the top of a liquid paint, caused by a chemical reaction to moisture in the air (partial curing or drying of the repellency).

Slip agent
Additive which reduces the friction coefficient and thereby improve slip characteristics of coating films. Various waxes, silicones or modified polyesters can be used to increase surface slip.

Solids by volume
Percentage of the total volume occupied by nonvolatile compounds.

Solids by weight
Percentage of the total weight occupied by nonvolatile compounds.

Solubilizate
Colloid form of dispersion between true solutions and emulsions. A solubilizate is formed when a water-insoluble liquid is added to water in the presence of an excessive amount of surfactant - more than is needed to form and stabilize a regular direct emulsion.

Solvent
Substance that dissolves other substances. Usually readily flammable volatile.
Syn. Diluent

Solvent entrapment
Coating defect: encapsulation of solvent within a cured coating due to improper formulation or drying conditions. Results in a non-continuous film.

Spray head
Combination of needle, tip, and air cap.

Spray pattern
Configuration of coating sprayed on the surface.

Special-effect pigment
Metal flake, pearlescent, sparkle and related pigment. Creates special optical effects such as metallic, Hammer finish and different color perception depending on the angle.

Spreading process
Flow of a coating composition over the substrate to be coated driven by a combination of forces, including the interfacial tension, gravity, mechanic shear, and inertia, and controlled by the viscosity of the coating composition.

Spread rate
Coverage, usually at the specified dry film thickness.

Stabilizing additive
Additive used to enhance coating durability and resistance to destructive factors and protect coating film from chemical and structural changes.

Streaks
Coating defect.
Syn. Brush marks

Stress corrosion cracking
Coating defect: spontaneous cracking produced by the combined action of corrosion and static stress.

Structural stabilizer
Additive used to stabilize the polymer structure of the binder.

Structural viscosity
See Thixotropy

Substrate
Surface to be coated.

Substrate wetting agent
Additive used to improve substrate wetting. Substrate wetting agents help in promoting spreading, enhancing adhesion durability, and eliminating coating defects.

Surfacer
Easy sanding paint used to fill depressions and surface irregularities in order to obtain a smooth, uniform surface before applying the finish coat.

Surface tension
Energy required to expand the surface of liquid by unit area (N.m-1 or J.m-2). Liquids tend to reduce their surface area due to unequal intermolecular attractive forces in this region.
Syn. Interfacial tension

Surface active agent
Syn. Surfactant

Surface conditioner
Additive used to provide improved mechanical, optical and electrical surface properties to organic coatings. Enhances anti-blocking properties, scratch and mar resistance, and imparts water-repellency. This type of additive is used in wood, decorative, powder and coil coatings and in industrial, can coatings, and inks.

Surface defect
Defect of a coating application. Gives coating bad appearance or performance. A coating defect can be caused by a lot of things such as poor substrate wetting, loss of flow, surface deformation, solvent evaporation, air...

Surface flow
Viscous distortion of a surface layer of a fluid driven by mechanical shear, gravity or surface tension.

Surface modifier
Additive used to enhance slip properties, anti-blocking properties, or abrasion and scratch of coating applications.
Syn. Surface conditioner

Surfactant (extended definition)
Additive which reduces surface tension thereby improving wetting or helping to disperse pigments or inhibit foam. Amphiphilic molecules of surfactants contain hydrophilic polar and hydrophobic apolar parts. They tend to adsorb at surfaces or interfaces.

Suspension
Relatively coarse, noncolloidal dispersion of solid particles in a liquid.