Cute cats, watch out. Photos of empty beer glasses are taking over the Twitterverse in the Twin Cities.

Maybe you've seen them. In early February, beer fans (geeks?) began tweeting images of their pint glasses -- with nothing in them but suds. Why? It's a Twitter movement created to spotlight bars that clean their glassware properly.

In a "beer clean" glass, the suds naturally lace around the interior, creating a creamy tapestry. (It's art!)

No suds? Dirty glass. OK, maybe "dirty" is too strong a word. A more appropriate description might be "soapy." The chemicals used by some bars (and a lack of scrubbing) can leave a residual trace, sometimes strong enough to taste. For the discerning palates of craft-beer devotees, that's blasphemous.

The cleaning crusade was started last year by Joe Falkowski, a tattooed beer salesman for J.J. Taylor, the Twin Cities' largest beer distributor. He started tweeting about clean glassware on a whim back in 2010. He soon persuaded the brass at his company to get behind the movement.

The annual push is back for February, with beer fans tweeting up a storm. After Feb. 29, the bar with the most Twitter mentions will be recognized as having the "Cleanest Pint in Minnesota." J.J. Taylor will also hand out prizes to tweeters. In each tweet, participants are adding the hashtag phrase #MNcleanpint, which allows other people (and J.J. Taylor) to search for tweets related to this topic.

"Dirty glassware is detrimental," Falkowski said. "You'll get soapy flavors. I've sent pints back that I can't even drink. I really hate doing that!"

Tweeting for a cause

The tweets are numbering in the hundreds now. Most are pretty straightforward. A Twitter user generally makes a comment like "Tasty!" or "Delicious!" followed by a photo and the hashtag.

Some tweets are more poetic: A user named @osier33 posted a photo and wrote "The ghost of @surlybrewing Furious," likening the blanket of leftover suds to an apparition. Has an Edgar Allan Poe ring to it.

Of course, there is potential in this movement to shame bars with dirty glassware (mockery being a central tenet of Twitter). Falkowski said that's not his aim.

"It's more about celebrating the bars that are doing a good job," he said. "The line between beer geek and beer snob is very thin. You don't want to come off being a jerk."

For Falkowski, it all started at the Muddy Pig. He remembers sitting at the St. Paul bar and admiring the ribbons of suds draping around his glass of Summit Horizon Red Ale. He snapped a photo that would launch a thousand tweets. Last year, Town Hall Brewery in Minneapolis generated the most tweets. This year, the Nomad Pub is in hot pursuit of the title.

Muddy Pig owner Mark van Wie welcomes the scrutiny brought on my #MNcleanpint.

"Joe got people talking about a very common issue," Van Wie said. "Hopefully every bar will take a little more care with cleaning their glassware. We all benefit from it."

So what's the science behind these leftover bubbles?

It's pretty simple, bar owners tell me. Beer suds will slide right off a soapy glass. But in a "beer clean" pint, the bubbles will stick.

"It's almost like a misnomer, because we're calling it a clean pint, but it looks dirty," Falkowski said.

Different cleaning methods

Certain detergents will leave a film on glassware that won't easily rinse off. It all depends on how the pint glasses are cleaned. Some bars use the three-sink dunk method. Others have carousel wash machines. A few go a step further. The Nomad and Pig & Fiddle have installed bar-top spritzers that shoot water up into an already-clean glass before filling it with beer.

Nomad owner Todd Smith told me, "I'm glad people are acknowledging our work."

In many ways, #MNcleanpint is just a further indication that beer lovers take their drinking as seriously as anyone. (I'm talking to you, wine snobs.)

The whole thing made me wonder: What's next, Twitter photos of clean draft lines? That's probably a bigger issue in bars. If bar owners don't clean their tap lines, bacteria and other nasty deposits can develop in there. A good flush is recommended every two weeks. And it's especially bad for bartenders to dip the tap faucet (where bacteria can build up) into the beer glass.

"Actually, that might be my No. 1 pet peeve," Falkowski said.

Hmm, I don't think my cellphone camera is small enough to fit inside a tap line.