Watch Old-School Single-Use Flash Bulbs Explode in Slow-Mo

Exploding flash bulb in slow motion

YouTuber Alec Watson of Technology Connections explored the fascinating history behind the single-use camera flashes of days past — and it’s a blast.

In the video, “Flash photography used to be pretty wild,” Watson and Gav from The Slow Mo Guys tests some old-school single-use flash bulbs and the Magicube, created in 1970 by Kodak and Sylvania.

The first consumer-friendly single-use flash bulbs were still a chore to use, however. The cost added up since they could only go off once, and they got extremely hot. On top of buying the flash bulbs, camera users of yesteryear also needed a flash unit to place the bulbs. The flash unit slotted into a camera’s hot shoe and had a reflector come out around the bulbs.

A bulb from a Magicube close up.

Enter flash cubes, which offered four flash bulbs in one. It also didn’t need a separate unit. Oh, and it was explosive.

As Watson explains, when the tube coming out of the bulb is struck quickly, the contents explode, creating the bright light needed to take a decent picture (to put it in simple terms). It was still quite expensive, though. A package of three Magicubes providing 12 flashes retailed for @.25, which would be about $18 today, Watson explains. That breaks down to $1.50 per flash on top of the cost of film and processing. Phew.

Sylvania Magicubes flash cubes in a line.

Watson’s video is fascinating, especially in how it breaks down both types of bulbs going off in slow motion. For this portion, Gav and his trusty Phantom high-speed camera help viewers see what the human eye usually can’t. Under close inspection, it’s possible to see smoke rising, the bulbs expanding and cracking, and pieces of the filament smoldering. Up close and using a camera recording an incredible 200,000 frames per second, viewers can observe what looks like bubbles of molten metal pop within the bulbs.

A single use flash bulb from a Magicube close up shows bubbles of metal.
At super-fast frame rates, Phantom cameras can’t record using the entire image area, which is why this screenshot has such a wide aspect ratio.

Sparks inside a Magicube bulb.

“A plume of sparks shot of from the base of the bulbs and ignited the zirconium, with the filings burning like brilliant fuses,” Watson remarks, watching the super slow-mo footage.

Eventually, Watson and Gav get a bit experimental and break open a single-use flash bulb to see what’s happening inside. They end up realizing that both types of bulbs actually use some “explosive” power to create the bright light of a flash.

“And people flew with these?” Gav asks toward the end with a laugh.

Image credits: Technology Connections