It is also clear that home-made masks such as teacloths may still confer a significant degree of protection, albeit less strong than surgical masks or FFP2 masks. Home made masks however would not suffer from limited supplies, and would not need additional resources to provide at large scale. Home made masks, and to a lesser degree surgical masks, are unlikely to confer much protection against transmission of small particles like droplet nuclei, but as the reproduction number of influenza may not be very high [14] a small reduction in transmissibility of the virus may be sufficient for reducing the reproduction number to a value smaller than 1 and thus extinguishing the epidemic
Translation - better than nothing. We don't own any tea cloths. I would think something with a high thread count and/or thick or multiple layers would make a difference. Especially multiple layers or pleated to create multiple layers would be decent. Just need a sewing pattern.
I have two drawers of tea towels. Fabric from the 1950s to today. The weave is too wide. A kleenex would be better. Did it say how many layers of tea towels?
Just read an article on making a mask from 3 layers of t-shirt fabric. IMO, again, too loose a weave and it stretches making the holes even larger.