For water-based paint the limit is the freezing point of water. Hempel's storage guideline says waterborne coatings should never be exposed to frost and that below freezing the paint is irreversibly destroyed; one winter night on an open truck is enough.
| Product | What cold does |
|---|---|
| Water-based paint | Irreversibly destroyed |
| Solvent-based paint | Resists frost, thickens, returns to its old consistency when slowly warmed |
| High-solids epoxy and polyurethane (two-component) | Binder may crystallise; warming and re-mixing are needed |
A tin that froze looks normal from outside. Lumps or a jelly-like mix on stirring and a faulty film on application show the damage, and by then the cost is labour and reapplication. Leave a load that has to wait overnight in a heated place, and get the limit figure from the supplier and write it on the delivery note.