|A square petri dish being used as a watercolor palette. Also works for gouache and gansai tambi.|
I've been looking for a mixing palette with a lid, and while there are quite a few I've seen in action and look quite snazzy, I've found that polystyrene plastic palettes come with lids, are cheaper than art store plastic palettes, and don't stain from phthalo or quinacridone colors. The petri dish shown above is 10 for $8.
These palettes also break in quickly, and after one use colors tend to bead up far less than with other plastic palettes.
You can get round petri dishes in various sizes (60mm is very portable but also small, while 100mm is quite sprawling), and even divided round petri dishes. But my favorites thus far are these square petri dishes. They're gridded, which can make it easier to separate and measure colors for mixing, though the inside of the dish is smooth—the grid is only on the outside.
With these petri dishes, I can save colors for multiple projects in their own dish (or set of dishes, I still keep my 60mm in case I need to mix up a medium sized wash), and they all come with their own covers to keep dust out of the paints. It's pretty perfect system, plus I can place the clear dishes over paper of the same color as my work and get even more accurate assessment than I would in a white or gray palette.
I haven't tried inks, so I have no idea if inks (especially permanent inks) or Inktense will stain. But inks are pretty runny so you're better off getting a porcelain palette with small, rounded wells.
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Ava Jarvis is an ink and watercolor artist with a portfolio site at avajarvisart.com. If you found this post useful, consider a one-time tip or supporting Ava on Patreon.