Since the coronavirus pandemic broke out, we have seen various versions of face masks people use to protect themselves against the virus, be it store-bought or homemade. But just how effective are these masks? To find out, a Japanese chemistry professor compared three different types of face masks in a science experiment: a surgical mask, a homemade paper towel mask and a homemade cloth mask. Dr Tomoaki Okuda, an associate professor of applied chemistry at Keio University, measured how well the three masks could block airborne particles using a Scanning Mobility Particle Sizer (SMPS). To put it simply, the hose...