Spraying money around?
Popular brands of aerosol sunscreens cost around $16–20 per can, and supermarket brands are about $9-10. Thanks to unit pricing on supermarket shelves, we can see this works out to about $8-11 per 100 grams for name brands, or about $5-6 per 100 grams for supermarket brands.
At first glance these prices may seem comparable to sunscreen lotions and creams. But the weight of the can includes the sunscreen product, which (mostly) lands on the skin, and aerosol propellants which disperse into the air when sprayed. On the other hand, a tube or bottle of sunscreen cream or lotion – or a pump-spray product – contains only the sunscreen.
To find out roughly how much of the can is sunscreen, versus the propellant, we did some tests.
First we weighed the can and a sheet of baking paper – this was our 'before' weight. We then sprayed sunscreen onto the paper, and weighed the can and paper again – our 'after' weight. The difference between the before and after weights was the weight of propellants and other volatile chemicals that disappeared into the air when we sprayed.
After repeating this many times, indoors and outdoors, we found that only 40-60% of the can was sunscreen. So you spray out 10 grams, about 4-6 grams of product ends up on the surface you're spraying. You may lose more to overspray, especially if it's windy or you're spraying a small area.
As a ballpark, then, doubling the cost per 100 grams of aerosol spray will give you a more realistic price for the product – and it may be surprisingly expensive.
Our backgrounder on spray sunscreens has more information about these products, including potential safety issues.