Oil on Masonite, 5 w x 5 h inches.
I took some liberties in painting, but most of the textures, color layering, and painted line details are pretty much what thick film birefringence looks like in the polarizing microscope.
If you have access to one, try this:
Take a thick soap paste or liquid wax. Place a drop onto a glass slide. Put a cover slip on top and gently tap to make a flat top. Look at in the the polarizing microscope.
There are lots of sources for birefringence and other optical effects in this type of thick film. They’re too complicated and messy to be good research samples, but they sure are pretty.