Phosphors radiate visible light after being energized. This means you have to expose the items to light for a while before they will glow in the dark. Phosphors then slowly release their stored energy over time. As they release the energy, they emit small amounts of light, which we see as an object glowing.
Pig bladders were used in the 19th century to store an artist’s paint. The bladder would be sealed with a string and then pricked to get the paint out. This option wasn’t the best because it would often break open. American painter John G. Rand was the innovator who made paint tubes from tin and screw cap in the 19th century.
Many modern 35 mm film projectors use three-blade shutters to give 72 images per second—each frame is flashed on screen three times. Motion picture film In the motion picture industry, where traditional film stock is used, the industry standard filming and projection formats are 24 frames per second (fps).