Here's a portrait of my son Frank, who is apprenticing at glassblowing.
It's fun to watch the process. Propane mixes with oxygen to make a powerful diagonal jet of fire that heats up and softens the glass. The stream of blue-colored flame turns to yellow-orange as soon as the glass touches it.
The warm light from the flame lit the front surfaces. Some cool fluorescents lit his back and the top of his head.
I used casein in a watercolor sketchbook held up on a camera tripod. Having the work up high, close to my line of sight, makes accurate judgments much easier. I liked where I was sitting because my work was lit by the window behind me. The brim of the hat shields my eyes from the dangerously bright orange light.