This is a start of a painting I am working on from my own reference of some flowers outside my apartment complex.
I worked up the composition quickly and have blocked in the area quickly, I will worry about refining it later but wanted to get the major shapes and flow of color in place. This is on cardboard that has begun to warp slightly from the casein paint, which is normal, but this painting is just a little something for myself for practice so I am not terribly concerned with how long it lasts (or I would have painted it on a more durable surface).
Working in Casein is a real joy, I love the fact that I can reactivate areas to rework as I see fit for the next few days, and my palette (of all 3 of my colors, Burnt Umber, Titanium White, and Ultramarine Blue) has been staying good for the past 3 days in a stay wet palette.
I used only a number 2 flat hog hair bristle brush for this so far, with my only medium being water. Casein has been the most wonderful kind of paint I have used besides oils, being everything I like about painting in other mediums without the drawbacks of any particular medium. Wish I had found it a decade ago as it is quickly becoming my go to medium for sketching, underpainting, and studies.