I had an old issue of either Superboy or Superman Family that had a story called 'The Origin of Superman's Uniform' where Superman told a reporter how his parents came up with idea for an indestructible suit for Clark to wear.
As an infant, Clark was always ruining his clothes, partially because he didn't know his own strength.
Then, one day, there was a fire in the barn and Pa Kent used the blankets from Clark's rocket ship to put out the flames. Pa discovered that the blankets didn't burn or scorch, but the fabric couldn't be cut with normal scissors, so he had to unravel each blanket by hand and then Clark used his heat vision to cut the threads, and Ma Kent sewed the uniform together. Rubber parts from the rocket, Clark molded into boots and glass from the canopy became the lenses for his glasses as they wouldn't melt if he used his heat vision. The cape comes with a pocket where Clark can compress his regular clothes into a tiny bundle. The writer also added the explanation that the Kryptonian fabric stretches as Clark grew; to try and explain why three small baby blankets could clothe a fully grown adult.
