As day two of BottleRock kicked off, festivalgoers sipped rosé, IPAs and tropical drinks out of hollowed coconuts under a sunny Napa sky.

While the third day of the festival was expected to be overcast and possibly rainy, the weather of day two was warm and breezy. Some spread out on blankets and basked in the sun.

Guests wandered about the numerous food trucks and vendors, deciding what to eat. People posed in giant letters spelling “LOVE” and kids twirled through a fog of bubbles near the entrance of the festival. Their parents looked forward to headliners such as Neil Young, Pharrell Williams and Juanes.

Marco Barba of Bakersfield said he got tickets because his girlfriend loved Neil Young and wanted to come to a festival. He also looked forward to seeing Cypress Hill, one of his favorite bands in high school and college.

Plus, he said, the weather and food was great.

BottleRock has “decent music for a food festival,” he quipped.

Frances Fort and Joe Cress of Sacramento said they have gone to many festivals, but were impressed with BottleRock’s lineup.

“We came for the music,” Fort said. “Like, the better music.”

While waiting for their favorite artists to come onstage, some people passed the time by getting their faces painted near the Firefox Stage at a booth hosted by the company. Face painters from San Francisco’s Happy Cake Face Painting were on hand with neon colors, sponges, makeup wipes and brushes — and lots of glitter.

At the front of the booth was a large monitor and a webcam that tracked the faces of people passing by.

But Alex Chan, a Firefox ambassador, went undetected. That’s because artists painted a design on his face that outsmarted the facial recognition software.

Firefox is an open-source, open-code browser that doesn’t track users or collect their data, Chan said.

The booth’s back wall read “Check yourself(ie)” and visitors could pick up buttons with the hashtag #privacyplease.

Some online companies have made a business of collecting data, Chan said.

“There’s a monetary aspect to it,” he said.

Face painting at the booth was free.

Artists worked at stations complete with laptops and webcams to allow visitors to check and see whether their design fooled the face recognition software. Designs painted across the face in a Z-shape tended to confuse computers the most, said artist Thao Ngo.

And while face painters had perfected their incognito looks, most visitors preferred flowers, stars or butterflies.

“Everyone wants to feel glammed up,” she said.

Brian Hinch of Tellart, a company that specializes in art installations, said the Firefox installation was meant to make people think critically about online privacy risks, including data harvested for advertisers.

A board next to the screen asked “Who is using your selfie?” and noted that pictures can be used for policing or employment, even without your consent.

Not all companies use such technology in bad ways, but people should be aware of the risks, Hinch said. People just need to be aware of what they’re opting into.

“Once people have some awareness ... then you can have a more nuanced conversation,” he said.

The issue of online privacy has been a hot topic in the news, from social media companies harvesting user data to company data breaches, Hinch said. There’s not a lot of transparency in how data is collected and people don’t seem to know how they feel about it.

“We’ve got to unpack it as a society to make any progress on it,” he said.

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Public Safety Reporter

Courtney Teague is the Napa Valley Register public safety reporter. She can be reached at 707-256-2221. You can follow her reporting on Twitter and Facebook, or send her anonymous tip at: tinyurl.com/anonymous-tipbox-courtney.