Watching paint dry

Traditionally the preserve of the bored observer, the paint drying process is jam-packed with chemistry

Paint basics

Paint has three basic ingredients: resin to form the paint film (this will be a natural or synthetic polymer known as the binder); pigment for colour; and solvent to dissolve the binders in order to get the right consistency.

Is paint drying really chemistry?

You may think solvent evaporation is the key to paint drying, and it can be. But chemical processes are harnessed to provide another way. Speciality paints might include two reactive epoxy binder components to mix together at the last minute, prompting a reaction to turn the two liquids into a solid. More run-of-the-mill paints will first evaporate to leave a sticky resin film (often an alkyd resin), which will auto-oxidise in air to leave a hard plastic solid.

Hidden hazards

Bang! Watch out all you DIY aficionados, drying paint can lead to spontaneous combustion. If your paint-soaked rag is left in a heap, the heat generated by auto-oxidation can’t escape and the resin, polymer or oil in the paint, can get hot enough to cause ignition.