'Chemical vs Physical' Is a Myth: Mineral Filters Absorb UV Too
The tidy story that mineral filters only 'reflect' UV while chemical filters 'absorb' it is largely wrong, and the truth is more interesting.
Contrary to the popular framing, titanium dioxide and zinc oxide absorb the majority of UV through their semiconductor electronic properties rather than merely reflecting or scattering it.
Materials scientists at BASF explain that mineral UV filters work largely by absorption tied to their semiconductor properties, and Stanford Medicine likewise notes the 'physical only reflects' framing oversimplifies how these filters actually behave.
Questions we get a lot
Do mineral sunscreens only reflect UV rays?
No. While zinc oxide and titanium dioxide do reflect and scatter some UV, they absorb the majority of it through their semiconductor electronic properties. Reflection accounts for only a small portion of their action. The idea that mineral filters merely 'bounce' UV away is a common but inaccurate simplification.
Is the 'chemical vs physical' distinction meaningful?
It is a loose label rather than a precise mechanism, because both filter types absorb UV. The cleaner difference is chemical makeup and feel, not 'reflect vs absorb.' As Stanford Medicine notes, the popular framing oversimplifies the science, so choose a sunscreen based on broad-spectrum protection and how well you tolerate it.
r/SkincareAddiction: 'I always heard mineral sunscreen sits on top and bounces UV away — is that not actually how zinc oxide works?'