Re: Any tips for keeping Casein palette active?
I haven't used casein all that much but do really like it. I've used gouache much more so I can compare a little bit.
I've kept casein on my StaWet palette for quite a long time - maybe a couple of weeks before it became unusable. I don't use the StaWet brand sponge but one that I picked up at the Dollar Store that's very similar. (I also use a generic paper palette on top). The sponge is only slightly damp and the paints are misted before storing. If I don't plan to paint for a few days, I also go back and mist the paints as needed. Adding a tiny bit of casein medium also really helps keep the paints usable.
As far as reactivation goes, the casein on your painting can be reactivated if they aren't completely dry but it's much less so than gouache. How much will depend on how dry the painting is.
I think you'll enjoy the new Casein paints but like any medium, there's a learning curve and you'll have to practice to find your way of best working with them.
Looking forward to seeing any painting you do with them and hearing how you like them! Have fun!