What is the expansion space in paint cans?

1. Thermal Expansion
During summer, in transportation or in warehouses exposed to the sun, the solvent inside the can evaporates, resulting in increased pressure. Leaving a 5% void space can reduce the pressure increase to <0.2 bar, preventing can bulging or lid bursting.
2. Cold Expansion
Water-based paint can freeze at temperatures below -5°C, expanding by approximately 9%; leaving a void space prevents ice crystals from cracking welds.
3. Transport Vibration
The jolting of trucks can create a "liquid hammer" impact. The void space can buffer the instantaneous pressure of the liquid on the can wall, reducing the risk of leakage.