OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION (OSHA):
An agency of the federal government that sets workplace health and safety standards for U.S. employees.

OIL-BASED PAINT:
Paints made with a drying oil, such as linseed, soya or tung oil, as the vehicle and binder, and mineral spirits or paint thinner as the thinning agent. They generally dry very hard, but take longer to dry than latex paints and require more time to recoat.

OPACITY:
The ability to keep light from passing through. A paint with a high opacity will hide the substrate well.

OPAQUE STAIN :
Exterior stain that obscures the natural color and grain of wood, but still allows the texture to show through. Generally, one coat is applied to bare wood.

ORGANIC:
Refers to a substance derived from living matter; the molecular structure contains carbon.

OXIDATION:
A chemical reaction with oxygen. For example, the drying of oils in oil-based paint, or the rusting of iron or steel.