I recently had to patch a large hole in a wall (a past owner of my house used shoddy workmanship and zero planning).
Over the weekend, I started painting the patched hole – primer, then house paint.
While painting, I started thinking – modern house paint is a pretty amazing mixture of chemicals. House paint needs to do and be a lot of things at different times – it needs to coat and stick to the paintbrush, it needs to coat the wall smoothly and consistently, hide everything underneath, dry quickly, achieve a specific surface texture, be resistant to fading, chipping, and sometimes even mold and moisture. Oh, and it needs to come off your tools easily when you’re finished painting.
Modern house paints can contain thousands of chemicals, I’ll cover the major parts:
Parts of house paint:
Solvent:
This is what keeps the paint liquid while it’s in the can, be runny enough that you can apply it to a wall, and then when the paint is on the wall, the solvent evaporates quickly and leaves behind all the other components. Depending on the type of paint you use, a different mix of solvents are used – with varying degrees of danger to people exposed to them.
Pigment:
Nearly all modern house paints contain titanium dioxide – it’s pure white, reflects light nicely, and hides everything underneath the paint you’re applying – it’s often called a hiding pigment.
Before we all realized how terrible lead paint can be, house paints widely used lead oxides as a pigment, binder, and to increase durability.
In addition to titanium dioxide, there are the color pigments – these can be anything from clays to engineered organic molecules.
Binder:
Most of what we think of as “paint” is just the binder: the latex, polymer, urethane, and/or enamel base of the paint that is left over when the solvent leaves. It’s called binder because it binds to the bare wall (and/or previous paint layers) and holds the pigment.
More info: wikipedia
(image by Flickr user M.A.R.K. – click image for more info)
