
Then I was just touching up a frame here and the light bulb flashed on in my brain: casein! You seem to be pleased with the medium as a full-service plein air sketch medium. I’ve never used it except on frames. But I have a full array of tube colors. Have you taken casein on a trip as your prime medium? When you travel with casein, do you work on watercolor paper? Or just in a sketchbook? And what have you used for a travel palette for casein? I guess the big issue I’d be concerned with is losing quantity of dry paint on the palette. (whereas gouache can kind of be re-wet)."
What do you think? I’d really appreciate your thoughts and experience with the medium.

Hi, Jim,
Like you, I don’t take my oils traveling as much as I used to, mainly because of TSA hassles and solvent, stains, and drying-time issues. I always take watercolor and water-soluble colored pencils in my most basic belt-pouch kit (I take this kit EVERYWHERE including the opera and the ballet!), but I add gouache or casein when I want to get more involved in opaques. I like the fact that I can ramp up from drawing to drawing-and-watercolor and then to watercolor-plus-opaque. This completely bridges the gap between drawing and painting.
Casein is an older medium than oil, and I'm told Egyptians used it, and that it actually conserves better than oil--no yellowing for one thing.
I usually work in hardbound watercolor-paper sketchbooks. The paper is beefy enough to handle full wet washes. Casein emulsion isn't that strong in impastos, so if you want to work with a lot of texture you need to either preload the whites with acrylic modeling paste or thick gesso or paint on a very solid surface. Unless you really gob on the impastos, there shouldn’t be any issues with cracking or adhesion. Of course you could work on stretched watercolor paper, board, or panel.
Gouache is probably better than casein for fine detail. I think casein lends itself best to bold opaque direct handling, as with the illustrators John Berkey and Harry Anderson. Some people don’t particularly like casein because of the “chalkiness,” the shift in drying colors, the matte surface, or the general lightness of the darks, but I love all those qualities.
Casein is also a good underpainting medium for oil. If you want a more oil-like surface with casein alone, you can varnish it. You can get casein emulsion and casein varnish. I've tried varnishing it, but I think the velvety matte surface has an attraction all its own.
There’s no way to rewet the dry paint on the palette, but you can keep it wet longer if you put it on a damp paper towel. I wouldn’t want to keep it wet on the palette for more than a few hours because of the risk of mold forming.
Other issues: it kills brushes, and has some ammonia in it, so you shouldn't use natural bristles or sables, but synthetics instead.
I use a variety of limited palettes, and usually only take out about five tubes at a time, just to keep life simpler. The last time I went out I took one similar to Stobart’s palette (Titanium white, ultramarine blue, pyrrole (Winsor) red, burnt sienna, cadmium yellow light, and permanent green). Are you familiar with that one?

One last thing: it has an unusual smell which you either like or don't like, but I've discovered that the smell attracts animals. Maybe it's the milk-based binder.

One last thing: it has an unusual smell which you either like or don't like, but I've discovered that the smell attracts animals. Maybe it's the milk-based binder.
All the best.
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Here's more about the tools I was using:
I was using Richeson / Shiva casein
1/4 inch flat brush
Moleskine watercolor notebook
Waterman Phileas red fountain pen
Lots of info on casein at Richeson's FAQ about casein
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Here's more about the tools I was using:
I was using Richeson / Shiva casein
1/4 inch flat brush
Moleskine watercolor notebook
Waterman Phileas red fountain pen
Lots of info on casein at Richeson's FAQ about casein