Do cloth face masks really work? We tested them in the lab

FRESNO, Calif. -- ABC30 teamed up with a Fresno State microbiologist in an attempt to settle the great mask debate.

Scientists have pointed to simple cloth masks as effective tools in slowing the coronavirus, but that hasn't quite settled the issue.

Two weeks into California's mask requirement, even one of Hollywood's scariest masked characters is promoting face coverings.

"Behind the mask, I'm just a regular guy," said Friday the 13th villain Jason Voorhees in a public service announcement designed to convince New Yorkers to wear a mask for protection.

But plenty of people are still fighting to free their faces and arguing masks don't help.

So we decided to check with the scientists.

Fresno State microbiologist Dr. Tricia Van Laar coughed and sneezed and talked into Petri dishes for us Wednesday.

"So, I'm just having a normal conversation," she said as she stood about three feet away and faced an open dish.

And then she put them away in an incubator. We waited 24 hours for a verdict.

When she took them out, we found no real surprises. The results aren't all dramatic, but they're clear.

"With my mask completely on, there are no colonies that grew on the plate," she said of the plate on which she sneezed while wearing a mask.

Sneezing spread the most bacteria, but a basic mask stopped it all.

Coughing and talking spread some bacteria too, but a mask also prevented it from spreading.

The coronavirus spreads in your respiratory droplets - the saliva and mucus you share with the world when you cough or sneeze or talk.

Viruses won't show up in these cultures, but bacteria act as a proxy because they'd help carry the virus.

"Especially with this SARS-coronavirus," said Dr. Van Laar. "It's surrounded by this envelope that's made of pretty much the same stuff bacterial cells are made of and your cells are made of, so if you can get rid of bacterial cells you have a really good chance of being able to disinfect for the virus as well."

Our experiment shows a mask helps get rid of both.

But even government scientists haven't always made that clear.

Coronavirus task force member Dr. Anthony Fauci admits some mixed messaging initially.

And President Trump has refused to wear a mask in public even as he announced the CDC recommends it.

"It's voluntary," he said at the April 3 press conference. "You don't have to do it."

But the tide has turned in recent days, with partisanship fading into the background and science stepping forward with clear evidence.