Re: paint, what does it contain? what are some of the main ingrediants in most paints?

Date: Mon Nov 6 10:19:18 2000
Posted By: Keith Allison, , dept: New Product, Technology & Development, Binney & Smith, Inc. (Crayola)
Area of science: Chemistry
ID: 972967277.Ch

Message:

Jerry,

There are three main ingredients in any paint:

solvent ("carrier"),
color,
and film-former ("resin" or polymer).

Solvents are liquids (alcohol, toluene, water, etc.) which carry the color. Nowadays, most paints are water-based, meaning that their solvent is mainly water. Color is added with either dye or pigment. More often pigment is used because it lasts longer. Finally, resins are added which give the paint various characteristics, including how the paint flows, dries, how smooth it looks, how it sticks to different surfaces, etc. Resins are polymers which come in all shapes and sizes; some are natural like gums or starches, and a lot are synthetic like acrylic polymers used in house paints. Other stuff that is added to paints: fillers like clay or opacifiers (make the paint hard to see through), surfactants (chemicals that help stabilize the paint so it lasts longer or brushes easier), "antimicrobial" agents (keeps bacteria and bugs from growing in water-based paint), etc.

In regards to how paints dry on a molecular level: imagine that the resin exists as tiny drops in the water surrounded by tiny surfactant molecules. Also imagine the pigment as tiny pebbles (particles) in the water surrounded by surfactants... Once you brush paint out onto a piece of paper or a wall for instance, the resin droplets begin to lay down onto the surface as the water or solvent begins to evaporate. The resin droplets then "coalesce" or migrate closer together and bind (stick) to each other. The pigment particles begin to stick to the resin. The resin droplets eventually fuse together into one long polymer film on the wall or paper, with the pigment particles trapped and stuck in it.

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