Coatings, Materials, and Color
A coating is a binder, pigment, carrier, and additives; the exam tests which is which and what thins what.
Families and thinners
- Waterborne acrylic and latex: thin and clean with water.
- Alkyd and oil: mineral spirits; longer open time, but they yellow.
- Two-component epoxy and urethane: pot life and a recoat window you must respect.
- Lacquer: lacquer thinner.
Sheen
Flat, eggshell, satin, semi-gloss, gloss. Higher sheen means a tighter film, easier scrubbing, and more visible defects.
Color
Hue, value (light to dark), and chroma (intensity). Undertones matter. Metamerism means a match under store light can shift outdoors. Bases are white, mid, and deep; a deep color in a white base will not develop.
Worked example: a product with 45 percent solids by volume applied at 3 mils dry film. Coverage = 1,604 x 0.45 / 3, about 241 sq ft per gallon. The 1,604 sq ft figure is the coverage of one gallon at 1 mil at 100 percent solids, so multiply by solids and divide by film thickness.
Traps
- Pouring water into alkyd.
- Adding thinner beyond the label limit.
- Tinting a deep color in the wrong base.
- Ignoring the recoat window on catalyzed products.
- Confusing grams per liter VOC with pounds per gallon.