When we started on Glowscreen, we'll admit we only knew we wanted the biggest number on the label. Then we learnt there are actually two numbers, and they're measuring two different things.
SPF is the sunburn number
SPF measures protection from the UV rays that cause sunburn, which are mostly UVB. It's tested by timing how long skin takes to redden under artificial sunlight, with and without sunscreen.
At SPF 15, roughly 1/15 of the burning rays reach your skin when it's applied properly. The higher the number, the smaller that slice.
PA is the UVA rating
UVA doesn't burn the way UVB does, so SPF doesn't tell you much about it. The PA system, used by many Asian and especially Japanese brands, grades UVA protection with plus signs.
- PA+
- UVA protection factor of 2 to 4
- PA++
- 4 to 8
- PA+++
- 8 to 16
- PA++++
- 16 or above. The top grade, added in 2013.
Which is why we wanted both numbers on one stick.
What's doing the work in Glowscreen
Glowscreen uses four UV filters together. Zinc oxide covers UVA and UVB, titanium dioxide mainly covers UVB, Uvinul A Plus absorbs UVA, and Tinosorb S absorbs both. You can read about each one in our Ingredient Corner.
Swipe it on 15 to 20 minutes before you head out, cover your face, neck and ears, and reapply every 2 hours and after swimming, sweating or towel drying. A hat and sunglasses still help on long days.