You open yesterday’s wet palette and find paint that still moves. That does not mean it has exactly the consistency it had at the end of the session. Before taking it back to a painting, give both the mixture and the palette a quick check.
A wet palette slows drying by keeping a suitable sheet over a damp reservoir. Its paper, foam and case have different care requirements. Redgrass’s foam-care instructions recommend gentle cleaning and thorough rinsing for its own material, and specifically warn against using paint removers or alcohol on the foam.
Do not clean every component the same way
Read the instructions for your palette and membrane. A method permitted for a hard plastic case may damage its absorbent insert. Remove old paint and replace or clean the working sheet as directed. Refresh the water rather than continually topping up a dirty reservoir.
Visible staining in foam is not automatically the same as active mould, but an unpleasant smell or growth deserves attention. Follow the maker’s cleaning and replacement guidance. Adding household chemicals to the water without instructions can change the materials and the paint you intend to use.
Test the paint on a spare surface
Take a small amount to a test scrap. Does it still cover, mix and brush as expected? If a saved colour has become watery or separated, do not assume it will match an earlier layer simply because it came from the same dab.
For a longer break, empty and dry the palette components according to their instructions instead of relying on a sealed lid to preserve them indefinitely. Keep notes of important colour mixtures separately; the palette should not be the only record of a colour you need to reproduce.
A clean setup and a short test stroke make returning to a project calmer. You can then decide whether the remaining paint is useful for the next passage or whether a fresh mix will give you a more predictable result.