ASE B2 Painting & Refinishing key terms

The underlying material being painted, such as steel, aluminum, plastic, or existing cured finish. Its condition and identity determine which cleaning, sanding, and primer steps are required before topcoat application.

A solvent blend applied before sanding to dissolve wax, silicone, oil, and road film from the surface. It is wiped on and off with clean cloths so contaminants are lifted away rather than spread.

A lint-free cloth treated with a sticky resin that picks up dust, sanding particles, and loose debris from a panel just before coating. It is used with light pressure after blowing off or vacuuming.

The abrasive particle size rating printed on sandpaper or discs; lower numbers cut faster and coarser, higher numbers polish finer. Coarse grits shape and strip, while finer grits prepare for primer or blend topcoats.

A gradual taper sanded into the border of a repaired area so the new coating transitions smoothly into the surrounding finish without a visible ridge. Poor feather edging shows through as a ring after topcoat.

A two-part polyester paste used to fill dents and low spots before priming. It is mixed with hardener, spread in thin layers, and sanded to shape once cured.

A coating applied over prepared bare metal or repaired areas to promote adhesion, provide corrosion protection, and build a uniform surface for topcoat. Primers are sanded smooth before color is applied.

A fast-drying coating sprayed over primer or old finish to create a uniform, nonporous base that prevents color bleed and improves topcoat holdout. It is often tinted to reduce the number of color coats needed.

A chemical treatment applied to bare metal that changes the surface chemistry to improve paint adhesion and corrosion resistance. It is used on aluminum and steel before primer.

An invisible oil residue that causes craters, fisheyes, and poor adhesion in a sprayed finish. It spreads easily from polishes, dressings, and shop aerosols, so thorough solvent cleaning and clean tools are essential.

The interchangeable nozzle at the front of a spray gun that meters liquid paint flow. Its size is chosen to match coating viscosity and type, with heavier primers needing larger openings than thin clears.

The tapered rod inside a spray gun that seats against the fluid tip and controls paint flow as the trigger is pulled. Needle and tip are matched as a set and replaced together when worn.

The front fitting on a spray gun that shapes and atomizes the paint stream through horn and center air holes. Its pattern and orientation must be cleaned and set correctly for an even fan.

The width and shape of the atomized paint cloud produced by the air cap. It is adjusted with the pattern knob and tested on paper so overlaps are even and edges are not heavy.

The technique of starting air before paint flow and stopping paint before air when moving the gun across a panel. It prevents heavy deposits at the start and end of each pass.

The amount each spray pass shares with the previous one, typically about fifty percent, so film thickness stays even. Too little overlap leaves streaks; too much builds runs and sags.

The spacing between the air cap and the panel during spraying, commonly six to eight inches. Too close causes runs and mottling; too far causes dry spray and rough texture.

A measure of a liquid's resistance to flow, often checked with a viscosity cup. Thick coatings atomize poorly and may need reducer, while thin coatings run easily and cover weakly.

A solvent added to a coating to lower viscosity for spraying and to control drying speed. The correct reducer grade is chosen for shop temperature and the product's technical data sheet.

A small cup with a calibrated hole used to time how long a mixed coating takes to drain. The measured seconds are compared with the product specification to confirm the mix is sprayable.

The specified proportion of base component to hardener, and sometimes reducer, for a multi-part product. It must be measured accurately because incorrect ratios cause curing, gloss, and durability failures.

The working time a mixed multi-part coating remains usable after the components are combined. Once exceeded, the product thickens or gels and must be discarded rather than thinned.

The catalyst component that reacts chemically with a base coating to cure it into a durable film. Its ratio to base is fixed by the manufacturer and cannot be adjusted for convenience.

The manufacturer document listing a product's mix ratio, pot life, recommended reducer, spray settings, dry times, and recoat windows. It is the authoritative reference for correct application.

The process of selecting or adjusting a coating so it matches an existing finish under the lighting where the vehicle will be viewed. It may require tinting, blending, or a variant formula.

An alternate factory formula for the same color code that accounts for production differences between plants or years. Technicians spray test cards of each variant to choose the closest match.

A small panel sprayed with a candidate color and compared against the vehicle in natural light. It reveals metamerism and flake orientation differences that a color chip may hide.

A condition where two colors appear to match under one light source but differ under another. It is why color checks should be done in daylight as well as under shop lighting.

A spray enclosure where filtered air enters at one end and exhausts at the opposite end, moving horizontally across the work. Airflow must be balanced to carry overspray away without disturbing the spray pattern.

A spray enclosure where filtered air enters from the ceiling and moves downward through a floor grate. This design carries overspray and solvent vapor away from the painter and reduces contamination on horizontal surfaces.

The media at the booth's air entry that traps dust and particles before air reaches the work. Loaded or torn intake filters reduce airflow and introduce contamination, so they are replaced on a schedule.

The media at the booth's air exit that captures overspray and keeps it out of the exhaust stack and environment. It must be changed when loaded to maintain airflow and legal emission compliance.

The relationship between intake and exhaust airflow that keeps the booth slightly negative so vapors stay inside. It is confirmed with a manometer or airflow gauge and corrected by adjusting dampers or filters.

The waiting period between coats during which solvents evaporate before the next layer is applied. Skipping it traps solvent and causes solvent pop, blushing, or poor adhesion.

The time range within which the next coat must be applied without sanding for proper adhesion. Applying outside the window requires abrading the surface first or the new coat may lift or peel.

A technique of fading a new color or clear coat into the surrounding original finish so no hard edge is visible. It reduces the area refinished and helps hide slight color differences on adjacent panels.

A bumpy, textured finish resembling citrus skin caused by paint failing to flow out before it sets. Common causes include thick film, fast reducer, low air pressure, and spraying too far from the panel.

A rough, sandy overspray texture caused by atomized droplets drying before they hit the surface. Holding the gun too far away, moving too fast, or using excessive air pressure produces it.

Small circular craters in a coating where the paint pulls away from a contaminated spot. Silicone, oil, or wax on the panel or in the air line is the usual cause and must be removed before recoating.

Tiny blisters or pinholes formed when trapped solvent boils out of a coating as it cures. It results from too little flash time, coats applied too wet, or excessive film build.

A sagging curtain of paint that flows downward before the film sets. Overspraying a pass, holding the gun too close, or applying too wet a coat causes it.

The final color and clear layers that provide appearance and weather protection over primer or sealer. Its quality depends on proper film build, flash time, and a clean spray environment.

A transparent topcoat applied over base color to provide gloss, UV protection, and depth. It requires accurate mix ratio and controlled flash time to cure hard and resist defects.