ITI/NCVT Painter General (AITT Theory) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Flash point

The lowest temperature at which a liquid gives off enough vapour to form an ignitable mixture with air near its surface; it is the key flammability rating for paints and thinners.

Isocyanate sensitisation

Repeated skin or inhalation exposure to isocyanate hardeners can make a person allergic, causing asthma-like reactions; supplied-air respiratory protection and gloves are required.

Putty knife use

A flexible-bladed scraper used to apply stoppers and fillers; hold it at about 30–45 degrees so the filler spreads evenly without ridges or drag marks.

Abrasive grit sequence

Abrasive paper is graded by grit number, where lower numbers are coarser; bare wood is typically worked from 60-80 grit up to 150-180 grit before priming.

Vernier least count

Least count equals one main-scale division divided by the number of vernier divisions; a 50-division vernier on a 1 mm scale reads to 0.02 mm.

Micrometer least count

Least count equals the screw pitch divided by the number of thimble divisions; a 0.5 mm pitch with 50 thimble divisions reads to 0.01 mm.

Blast cleaning grade Sa 2½

A very thorough blast cleaning in which mill scale, rust and foreign matter are removed, leaving only light shadows; it is the usual specification before protective coating.

Knotting

A shellac-based sealer applied over resinous knots in wood before priming, preventing resin from bleeding through and staining the finished paint film.

Volume solids

The percentage of a wet paint film that remains as dry film after the solvent evaporates; it is used to calculate spreading rate and dry film thickness.

Pot life

The usable working time of a mixed two-pack product before it thickens or gels; the batch must be discarded after this time and never thinned to extend it.

Spreading rate formula

Theoretical coverage in square metres per litre equals volume solids percent multiplied by ten, then divided by the required dry film thickness in micrometres.

Laying off

The final light brush strokes in one direction after paint is applied, levelling the film and removing brush marks for a uniform finish.

Spray gun distance

The gun is normally held 200-300 mm from the surface, perpendicular to it, with about 50 percent overlap per pass to give an even coat.

Orange peel defect

A stippled, uneven spray film resembling orange skin, caused by paint that is too thick, too little atomising air, or an incorrect thinner.

Compressor air dryer

Equipment that removes moisture from compressed air before it reaches the spray gun; water in the line causes fisheyes, blisters and poor adhesion.

Downdraught spray booth

A booth that draws filtered air from the ceiling down through a filtered floor, carrying overspray away from the wet film and the operator.

Scumble glaze

A translucent oil-based glaze applied over a dry ground coat and worked with combs or brushes to imitate wood grain, then protected with clear varnish.

Wood graining

A decorative technique using a ground colour, a glaze and graining tools to draw and soften grain lines that imitate a chosen wood species.

Fisheye defect

Small circular craters in a coating caused by oil, silicone or moisture contamination of the surface or air supply, which prevent the paint from wetting the spot.

Blooming defect

A milky haze and loss of gloss on a dried film, usually varnish, caused by moisture condensing on the surface during drying in damp, cold conditions.

Metamerism

A condition where two colours appear to match under one light source but differ under another, because their pigment combinations reflect different spectra.

Tinting strength

The colouring power of a pigment; strong pigments such as phthalocyanine blue or carbon black tint a batch with only a very small addition.

Zinc-rich primer

A primer containing at least about 80 percent zinc in the dry film, which protects steel galvanically by corroding in preference to the steel beneath.

Intumescent coating

A fire-protective coating that swells on heating to form an insulating char layer; its thickness is calculated from the steel section factor and fire rating.

Barrier protection

A coating prevents corrosion by sealing the steel from water and oxygen; performance depends on low permeability and adequate dry film thickness.

Sacrificial protection

Galvanising and zinc-rich primers protect steel because the zinc corrodes preferentially, acting as the anode in the electrochemical corrosion cell.

Paint quantity formula

Litres required equals total area in square metres multiplied by the number of coats, divided by the spreading rate in square metres per litre.

Pipe surface area

The external area of a pipe equals pi multiplied by the outside diameter multiplied by the length; end areas are added only if they are coated.

5S housekeeping

A workplace organisation method: Sort, Set in order, Shine, Standardise and Sustain; in a paint shop it reduces accidents, dust and material waste.

Job card discipline

Following the written job card, recording materials used and reporting errors promptly; it keeps work traceable and prevents coating failures from wrong products.

Safety data sheet sections

A standardised document with 16 numbered sections; Section 2 covers hazard identification, Section 4 first aid, and Sections 7-8 handling and exposure controls.

Spreadsheet estimation

Entering area, spreading rate and rate per litre in separate cells with formulas, so that changing one input automatically recalculates the material quantity and cost.