PORTLAND – A pair of Mainers who became Internet celebrities by plopping Mentos into Diet Coke to create geysers are about to become hits on mainstream media.

Fritz Grobe, 37, and Stephen Voltz, 48, were scheduled to appear on David Letterman’s show Thursday night and on the Today show Friday morning to demonstrate their explosive and entertaining chemistry experiments featuring candy and soda.

The Buckfield residents have had more than 3.5 million hits on their Web site since they posted a 3-minute video of their homemade experiment involving more than 500 Mentos and more than 100 two-liter plastic bottles of Diet Coke in early June.

“This has turned into a global phenomenon in a way that was totally unexpected. We expected to tell our friends, who would tell their friends, and then maybe a few weeks later we would start seeing some larger interest. But we never anticipated this,” Grobe said Wednesday.

Grobe and Voltz are known around Maine for their regular appearances as part of “The Early Evening Show” at the Oddfellow Theater, a 156-seat theater in Buckfield.

Their Mentos-Diet Coke experiment began on a whim eight months ago. “Stephen heard from a friend that if you drop Mentos in soda it makes a fountain,” Grobe said.

“We tried it like so many others have, and said, ‘This is really cool,'” he said.

They started with 10 bottles and saw the potential for more. “We knew there were so many more possibilities. We were just scratching the surface,” he said.

The geysers created on their video look like choreographed fireworks or the dancing fountain at Bellagio Hotel in Las Vegas.

On Letterman’s show, they hoped to use 120 bottles of soda, if time permits.

Grobe said it isn’t essential to use a Coke product, although diet soda seems to work better than regular soda, he said. “And don’t forget Moxie,” he said of the soft drink that originated in Maine. “Moxie works very well, as well.”

On the Net: www.eepybird.com