Watercolour, Gouache & Ink Palettes
Watercolour and Gouache are re-wettable mediums, which means that if they dry out on the palette they are still usable at a later stage. Watercolour palettes are designed with "wells" to store the paint in. In doing so the paint can remain on the palette and simply be topped up from a paint tube as it runs low. the liquid-like consistency of these paints usually requires a well to contain the colour or colours to be mixed.
Apart from the material they are manufactured from, the other main differences across the range is the number of wells and the convenience of a lid for storage and travelling purposes.