The difference between paint and stain can be looked at in two ways: the appearance wanted from the job, and product the formulation. With a stained appearance, one is usually looking to obtain a certain color of the substrate, while still seeing the texture of the material. Thus, if you stain wood or concrete, for example, you still expect to see the texture of the wood or concrete, while imparting a different color.
Exterior stains have two general classifications: 1) semi-transparent and 2) solid color (or "opaque"). With a semi-transparent stain applied to wood, we expect to see the wood grain and its texture, whereas with a solid color stain, the grain will be hidden while the texture will still normally be noticeable. With a painted appearance, we have created a new surface that completely hides the old surface, and has its own appearance, which is usually smooth, though textured paints are certainly used a lot.
The paint job often includes a primer coat and a finish coat, whereas the stain job will not normally have a primer, unless there is concern about excessive discoloration from tannin bleed-through. The product formulations differ in a broad sense in that stains (especially the semi-transparent types) are less highly pigmented than are paints. Most semi-transparent stains are oil-based, though some latex products are available. Opaque stains are much more like paints in their pigmentation; and like paints, are available in latex and oil-based formulations.
Oil-based stains are formulated for maximum penetra-tion of the substrate; compared with paints, exterior stains tend to be lower in viscosity (thickness) than paints, and are formulated for good lapping properties. For exterior applications (siding, concrete, decks, windows, trim, etc.), semi-transparent and solid color stains are generally applied without a clear finish coat. For interior applications (floors, doors and trim, furniture), most stains are oil-based semi-transparent wiping stains that are applied to bare wood, then immediately wiped off with a rag to reveal the grain; once thoroughly dry, a protective clear coating is generally applied.
Note: rags used to apply oil-based stains, paints, etc., may catch fire by spontaneous combustion if not disposed of properly. They should not be wadded up and put aside, but rather either spread out to dry in a safe place away from children, pets and any source of spark or fire; or put into a fire-proof container.