Kodachrome is stable as long as it’s in darkness. Light fades them pretty quickly. Back in the day originals would be on Kodachrome, from which copies would be

Kodachrome is stable as long as it’s in darkness. Light fades them pretty quickly. Back in the day originals would be on Kodachrome, from which copies would be made on Ektachrome for projection in slide displays or an inter-negative on Kodacolor for enlarging.