LIGHT

The body reads light as a signal, not just brightness to see by. Morning exposure to natural daylight helps regulate melatonin, the hormone that governs when the body feels ready for sleep, and keeps the internal clock aligned with the actual time of day. Research on people's own homes has found that more daytime access to daylight is associated with better-aligned circadian rhythms and better sleep at night. The same mechanism works in reverse after dark: light heavy in blue wavelengths, the kind most white and daylight-toned bulbs produce, has been shown to suppress melatonin even at fairly low brightness, while warmer, amber-toned light does far less to interrupt it. A room lit the same cool white all evening is quietly working against the body's own signal to wind down.

WHAT LIGHT DOES

Light has a second, quieter effect indoors, one that has nothing to do with how a person feels and everything to do with how an object ages. Ultraviolet light is the main driver: it breaks down pigments and finishes at a molecular level, which is why wood dulls and shifts color over years of sun exposure, and why leather dries and stiffens in the same way. Ordinary window glass blocks most UVB but lets a meaningful amount of UVA through, so a piece doesn't need direct sun to fade, just a spot near a window it sits in every day. A cyanotype print makes the point especially clearly: the same light sensitivity that makes the process possible in the first place is exactly what keeps fading the image long after it's framed.​