Reusable vacuum cleaner bags are the best material for making homemade face masks with, the University of Cambridge has concluded after testing everything from socks to jeans. 

The cloth bags, which can be cleaned in the washing machine, were found to be the best at preventing droplets and aerosols from escaping while still enabling wearers to breathe sufficiently well. 

Although some materials, such as thick denim and polyester, were better at stopping the spread of ultra-fine airborne particles, they made breathing too difficult to be useful. 

“A mask which blocks particles really well but restricts your breathing isn’t an effective mask,” said the study’s first author Eugenia O’Kelly, a doctoral candidate from Cambridge’s department of engineering. 

“Denim, for example, was quite effective at blocking particles, but it’s difficult to breathe through so it’s probably not a good idea to make a mask out of an old pair of jeans.”

While there are numerous online patterns to guide people through making their own masks, there is little scientific evidence on what the most suitable materials are.

To find out, researchers placed a fabric sample between two sections of tubing and sent through tiny aerolised particles at high speeds, comparable to someone coughing or breathing heavily.

Finally, they asked wearers to comment on how well they could breathe through each of the materials to calculate an overall score. 

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