Chapter 8: Watching Paint Dry

“Things aren't like they used to be – thank goodness”. The bad old days of paints are gone and modern paints do an amazingly good job because they harness all the principles of good adhesion discussed in earlier chapters. One of the keys to modern water-based paint is that the semi-solid emulsion particles are able to join together (coalesce) to produce a tough, resilient film. That's easy enough, but then you need to keep lots of pigments happily dispersed through the paint, the film needs to get stronger as it ages, it must tangle with whatever is beneath it (wood, plasterboard, metal, paint primer) and it must contain the minimum of volatile organic compounds. Automotive paints take things to a higher level because they achieve so many different goals (rust proofing, smoothing, being chip resistant, adding a great look and feel) via a chain of specific formulations for each paint layer. Even the best paint can be ruined by bad application. A paint that is too runny or too thick is a challenge, so we need “thixotropic” paints that adjust themselves as you paint. As a bonus you get to know why it is a false economy to buy a cheap paintbrush.