CBC's Conrad Collaco speaks with Dr. Catherine Clase, an Associate Professor of Medicine at McMaster University and a Nephrologist at St. Joseph's Healthcare Hamilton. She and her team looked through a century of research on cloth masks to find out how effective they have been in the past. 

They found, Clase said, that while there's no perfect face covering, masks with a layer of flannel sandwiched between muslin were extremely effective. Cotton was also found to be a strong material. Multiple layers of cloth seem to even be enough.