You can get acquainted with the process of work in the Instagram https://www.instagram.com/merlin.lightpainting/
I'm doing this paintings using only light, It is called Light painting. Light painting is a photography technique that uses a moving light source (such as a flashlight, laser, fiber optic filament) to add light to a subject when shooting at a slow shutter speed.
this photo is the beginning of a long collection of works, you can get a video of the process of creating this photo on my instagram