SECRETS OF PAINT AND STAIN CHEMISTRY

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PROGRESS

To their credit, today's paint industry inherited its problems from earlier generations, and has been more than cooperative with regulators in making their products safe as reasonably possible for consumer use. But many common products remain environmental hazards, and a few still pose danger to human health.

But, how to judge? Finishings chemistry is technical, making it difficult for most of us to shop knowledgeably for paints, putty, stains, and paint removers. Would you know the difference between (the common solvents) alcohol, ethanol, and methanol? Neither would I, offhand. They are three names for the same thing. Ethanol is common grain alcohol, the solvent used in shellac or "spirit varnish." It is usually laced with methanol ("wood alcohol" that was originally brewed from wood fiber). Methanol is poison—rendering the mix of alcohols "denatured," or unconsumable and indivisible—thus untaxable as distilled spirits.

SECRECY

Furthermore, paint making is shrouded in secrecy, harking back to medieval alchemists and their potions concocted from ordinary compounds and given arcane names: brimstone (sulfur), saltpetre or nitre (ordinary potassium nitrate used for centuries to make comed beef) as well as eye of newt and wing of bat. Further, paint makers are not required to list ingredients on paint or stain containers, and most of us are so ignorant of paint's mysteries that we have to buy whatever the hardware store clerk recommends.

In truth, there's nothing mysterious about conventional paint. It contains a fluid medium or solvent to flow it on, a white filler to give it body, and a white color base—plus a binder to provide smooth consistency and adhesion, and colored pigment. Its purpose beyond ornamentation is to bond with wood or other material to provide protection from corrosion on metal, and from water and ultraviolet sun rays on anything left outdoors. It's also meant to reduce the atmospheric-moisture retention/evaporation that combines with heat variation to cause continual joint destroying movement in wood.

Stains are even simpler. They provide both protection and ornamental enhancement to wood, and can be pure solvent such as Tung oil; a solvent/stain mix such as walnut oil; a mixture of solvent and natural pigment such as an earth color; or a synthesized pigment such as aniline dye.

For centuries red and white leads were mixed into paints because they are cheap, highly stable filler/binders—extremely fine powders that mix well with oil-soluble dyes, stay suspended in a linseed oil medium for extended periods, flow on smoothly, and adhere well to porous surfaces. They just happen to be toxic—but maybe in earlier times little kids weren't left alone to teethe on flaking window sills.

Dirt-common (literally) painter's lime or pipe clay are also finely milled powders that make almost as good a base pigment/filler as white lead. These benign natural earths will mix with water and absorb water-soluble pigments, but need starch or another cohesive binder to keep them from settling quickly, allow them to be applied smoothly, and make them stick. However, they are harder to mix and keep mixed and don't flow as smoothly. The organic binders in the paint (unlike waxy, toxic metallic lead salts) attract mold, and the finish will dry out and chip relatively quickly.

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