List your oil layers from the bottom up. Each layer should carry at least as much oil as the one beneath it and dry no faster. Times use the pigment, oil, temperature and humidity from Estimate.
| Layer | Mix | Paint it from |
|---|
| Property | Oil | Acrylic |
|---|---|---|
| How it dries | Oxidation: the oil absorbs oxygen and cross-links into a solid film | Evaporation: water leaves and the polymer particles fuse |
| Working time | Hours to days | Minutes; longer with retarder or open acrylics |
| Touch-dry, normal layer | About 2–5 days at room temperature | About 20–60 minutes |
| Varnish | Traditionally after 6–12 months | After about 3 days to 2 weeks, over an isolation coat |
| Layer rule | Fat over lean; slow-drying over fast-drying | No fat-over-lean rule |
| Humidity | Small effect | Large effect — damp air slows drying a lot |
| Cold | Slows curing; skins may wrinkle | Below about 10 °C (50 °F) the film may not form properly |
| Color on drying | Stays close; dull "sunk-in" patches can appear | Darkens slightly as the milky binder turns clear |
| Combining | Oil over an acrylic ground is fine | Never acrylic over oil paint |
| Clean-up | Solvent, or oil then soap and water | Water while wet |
Estimates are ranges for typical studio conditions with moving air. Pigment load, ground absorbency, airflow and brand formulas all shift real drying times — test a corner before you varnish.