One Panel #505: What Is Star-Spangled Kid's Costume Made Of?

From Star-Spangled Kid: "The Flying Buzz Saw" by Jerry Siegel and Hal Sherman, Star-Spangled Comics #4 (January 1942)

In Star-Spangled Comics #4, we find out it's made of silk. How fancy. Not only is it the perfect insulator for handling electrified traps, but it's also super soft on the skin. Other superheroes have to deal with rashes and harsh burlap burns.

Lace undies complete the outfit.