Cross-section of an oil paint layer with arrows of oxygen coming down from the air: the surface dries first while the paint below stays soft longer, very slowly when thick; it is dry to the touch in days and keeps hardening for years.

Concept · Working With Each

Oil Cures

Oil cures: it reacts with oxygen in the air, and its molecules link into one solid network.

Follow the arrows: oxygen reaches the top first, so the paint underneath lags behind, most of all in thick paint.

  • Driers added to the paint speed the reaction.
  • Cured oil can't be thinned back into wet paint.
  • In a 2022 lab study, oil paint films were still stiffening after 30 years.

Image: Made for this site · Original work

11 / 38