Answer: Aluminum Powder

The special effects found in the original Star Trek looked futuristic on the screen, but were surprisingly low-tech in real life. The automatic doors located around the ship, for example, were anything but automatic. They were actually opened by a film crew member yanking on the main control wire, which activated the wires running through the pulleys and opened the doors. Many of the bloopers from the show hinged on a film crew member daydreaming at their post and letting an actor walk right into the still closed doors.

In this regard, the transporter system on the Starship Enterprise was no different. The actors and actresses on the show would walk up onto the transporter platform, take their places, be filmed for a few moments, and then—as the audience would later see it—be beamed down for some exciting adventure on the planet below. In reality, the actors and actresses would simply step down off of the transporter platform and then, during post-processing, a sort of compositing magic would happen.

The modern CGI-wizardy we take for granted in the 21st century simply didn’t exist back in the 1960s. The sparkling effect you witness when watching old Star Trek episodes was executed in a very analog fashion. The special effect was created by Darrell Addison Anderson of the Howard Anderson Company, a popular optical effects production company.

To create the effect, Anderson set up a slow-motion camera, turned it upside down, and pointed it at a dark production stage. He then backlit the focal plane and sifted grains of aluminum powder down through the frame creating a sort of sparkling snow effect. This footage was then later, using an analog masking and post-processing technique, layered over the outline of the actors. If you’ve ever wondered why the transporter seems to freeze the people in place before beaming them down, it’s because compositing the image over a moving actor was simply too time-consuming. Freeze framing them allowed the film crew to use just a single mask in order to create the effect.

When you see the crew beam down in a burst of shimmering light and atomic rearrangement, what you’re actually seeing is light shining off thousands of grains of aluminum powder backlit with a high power stage lamp.