A year ago, Slate stepped up its video game, committing to twice daily, quick-turnaround pieces on water-cooler talk and memes of the moment. The Trending News Channel, born in December 2010, turned out to be a decent traffic draw for Slate.com, bringing in between 500,000 and 750,000 video plays a month in 2011.

But traffic really took off in March, when Slate began cross-posting the content to its YouTube channel. Those videos have accrued about 18 million views since then.

Today, Slate is one of more than 100 media partners who begin rolling out new, exclusive video channels in a deal with YouTube, which reportedly spent more than $100 million to become a major source of original content. Slate’s slice is called the Slate News Channel.

As part of the deal, Slate is expanding the TNC franchise, producing three stories per day about politics, science, and tech (topics they’ve found tend to draw bigger audiences). And for the first time, Slate will bring its famous Explainer series to video once a week, starting with a videxplainer on how commercial pilots “make up time” in the air.

The video explainer was YouTube’s idea, said Bill Smee, the executive producer of Slate’s video unit, Slate V. “When we pitched the idea of a news channel, they were like, what about the Explainer?” Smee said. “It may be boneheaded that we didn’t do this sooner, since it is one of Slate’s signature franchises, and certainly it makes sense to turn it into a video format.”

The arrangement is novel. YouTube commissioned Slate for the work with a “sizable check,” Smee said — not as sizable as what YouTube might be paying fellow launch partners Shaq and Madonna, perhaps, but sizable enough to cover Slate’s production costs. While Slate ultimately retains ownership of the content, the videos must live exclusively on youtube.com for the first year. YouTube recoups the initial cost by selling advertising. If and when YouTube breaks even, Slate is entitled to a revenue share for every additional dollar, Smee said. The YouTube-exclusive stories will be produced in addition to the two stories a day Slate is already producing for its own site.

To review: Slate spends nothing to produce the content, and if that content is engaging enough to attract eyeballs and advertisers, Slate eventually makes a little profit.

“There’s still a tremendous number of people out there who still don’t know that Slate makes video.”

Back in 2010 and early 2011, Smee said he was a little queasy about Slate potentially cannibalizing its own video traffic by cross-posting to YouTube. That feels like a long time ago. “That’s just no longer a consideration. We see this as added audience,” he said.

“It’s an opportunity for us to build the franchise out. We’re going on five years of making video at Slate. There’s still a tremendous number of people out there who still don’t know that Slate makes video, original video.”

The YouTube deal is a step away from the old-fashioned insistence that a content producer’s work must live on the content producer’s domain. (An insistence, to be fair, inspired in large part by a reliance on ad impressions.)

Smee said Slate’s news videos have an audience because they are “of the web.” They are meme-ish and disposable; they tend not to be stories that hit A1 but “things that might be a little quirkier,” Smee said. Yesterday’s 31-second piece about Rupert Murdoch’s new Twitter account will probably feel stale by tomorrow. Last Thursday’s 47-second piece about the death of Cheetah the chimp feels ancient.

That’s unusual, because video is not as versatile as tweets or text; it takes more time to produce. But Smee’s team has created something of an assembly line. The team initially spent a lot of time building a production template using After Effects and Final Cut Pro, which lets producers create stories with color-by-numbers ease. Writing the scripts takes about 20 to 30 minutes apiece. Then the scripts go to copy edit and narration. Slate produces two pieces a day in about three to four hours each, he said.

“We’ve created a kind of visual voice and style that I think works well on the web,” Smee said. “We are not like some legacy media organizations that are creating video from an old-school playbook — my background, by the way, is television, I was in television for 20 years, so I don’t sit in sneering judgment of television — but I do think TV and print organizations that have come to the web have not tended to kind of experiment with the form in the way ways that I think we have.”