I bought an actual glass palette two years ago. Grey, nice weight, cost more than I want to admit. It lives in the closet now because I ended up using a rimmed aluminum cookie sheet from the dollar store instead.

The rim is the whole point. I work wet into wet a lot and the sheet keeps the puddles contained, so I'm not chasing a run of burnt sienna across the table at 10pm. Also it's big enough that I can keep a muddy corner on one end and clean mixes on the other, which I could never do on the glass one.

It's stained now. There's a permanent greenish ring in one corner from a mix I made in March and a scratch from where I scraped it with a palette knife instead of being patient.

Anyway I have a workshop coming up in two weeks, first one since last fall, and I'm already dreading being the person who shows up with a cookie sheet and a plastic cup for water while everyone else has the nice setup. Then I remember I'm 42 and nobody cares.