Here I am, demonstrating how a Sundrop is made. I use a 31"x41" fresnel lens, which is made of 1/8" thick plastic with grooves in concentric rings, to focus sunlight. Fresnel lenses were originally designed for lighthouses, to disperse light. By flipping the lens over, it concentrates light instead. On a clear day like in the video, the focal point can reach 3000°F.
Here's a close up view of red glass melting in the 3000°F focal point of the giant magnifying glass.
Shaun demonstrates how to make a single color Sundrop. He places a strip of purple stained glass in the focal point, melts a blob of glass on the end, and allows gravity to pull the molten glass into a perfect Sundrop shape.