Starbucks will shut its more than 8,000 U.S. locations on Tuesday for an afternoon of racial-bias education for staffers, after video of the arrest of two black men at a Philadelphia store for trespassing kindled a national backlash against the company.

The coffee chain released a five-minute video preview of what 175,000 staffers can expect during the four-hour "conversation and learning session on race, bias and the building of a diverse welcoming company." At each coffee shop, the session will rely heavily on videos — including one hosted by rapper Common — as well as discussions among groups of three to five staff members and exercises in a workbook, Starbucks said.

Experts see the bias training as a good first step — but only if the effort doesn't stop at the end of the day on Tuesday.

"One of the things that Starbucks has made very clear, and I think it's critical to do so, is that this training has to be ongoing," Georgina Dodge, associate provost for diversity, equity and inclusion at Bucknell University, told NBC News. "The four hours will be important to set the stage, but I don't think we could expect someone to change their worldview in that amount of time."

Starbucks' training session, announced last month, comes after the arrest of two black men who were told to leave a downtown Philadelphia location of the coffee shop, despite their protests that they were customers who were waiting for a business associate before ordering.

The company-wide training will focus on a basic understanding of racial bias and its history in public spaces in the U.S. It's part of the company's vision of Starbucks as a "Third Place" where people feel as comfortable as they do at home or at work.

"This effort, and I'm going to call it an effort, it really appeals to the eternal optimist in me because what if this does become a space where discourse can be held?" Dodge said. "Because there aren't that many places like that in our society, where people can gather and have necessary conversations."