I’ve looked into this before. There are several ways of achieving this kind of effect. The first is simply using translucent paints. The second is to use a ‘glaze’ that has to be fired and forms a permanent bond with the glass.

The second gives less consistent, but more permanent results. And is very, very technically challenging.

I am fairly certainly that the large lines are the lead came, and the smaller black lines are an opaque glaze. So the head and hair, for instance, are a single piece that was probably a peach-colored glass that was then painted with glaze–the hair is a built-up color from the base–fired, and soldered into place. The garment appears to use a different color of glass as the base, with built up shadows, fine lines, and (I think?) a white glaze for highlights.

It’s an artform that requires a high degree of technical mastery over multiple different elements. It’s a pity that it’s so rare to see this kind of work anymore. Then again, I’d never be able to afford it, so…

I’ve never seen that level of shading and different tones in individual panes of stained glass.