ST. PETERSBURG — People usually have three reactions when they use a credit card at Marina Williams' art gallery and vintage shop on Central Avenue.
Bewilderment. A gasp. Then a squeal.
Paying with plastic at Williams' shop, ARTpool Gallery, is futuristic and a little weird.
Williams and a growing number of other Tampa Bay area businesses are embracing a growing trend in business that can save them money on credit or debit card transaction fees while amusing their customers.
All customers have to do is sign the screen — with their finger.
"They're all like, 'Oooh, I get to sign my name with my finger?' " said Williams, who has been using Square for about two months. "Some of them try to get really precise. Others just go for it."
After the transaction is done, the customer can have a receipt sent to her or his phone or email. No paper needed.
"They always say it's the coolest thing they've ever seen," said Dave Ward, who owns Buddy Brew Coffee in Tampa.
Ward and his wife, Susan, have been using Square at their business since it came out in October 2010. The couple also incorporate iPads into their point-of-sale process.
Ward, a self-described "tech guy," said he heard rumors about Square even before it hit the market. He was intrigued, and wondered how much of an impact it might have on his own business. He said before getting Square, he had a traditional credit card machine with a merchant account.
But most services, Ward said, charge not only a flat monthly fee but also varying percentages of a purchase, depending on what kind of credit card is used.
Square, he said, does neither of those things. Instead, it takes a flat fee of 2.75 percent of a purchase, regardless of what type of card is swiped. And the application and card reader are free.
"Square ended up saving us between $4,000 and $5,000 a year," Ward said. "That's huge. I think it's especially good for small, independent businesses."
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Even the Salvation Army used the device to collect holiday donations in big cities around the country, though not in the Tampa Bay area.
But company officials said the devices are popular here with more than 3,600 active Square users in the area. They include Safari Choppers, a helicopter tour company in St. Petersburg, and Rover Done Over, a mobile pet grooming business in Tampa.
Tampa is one of the top 20 cities in the country when it comes to activations by population, Square spokesman Lindsay Wiese said.
"Someone told me the other day they were at a yard sale and they had one," Williams said.
Still, not everyone is as impressed.
Cheong Choi, one of the owners of Cafe Hey in Tampa, said his business used Square for a few months instead of a traditional credit card machine.
The technology was good, he said, but there were a few glitches when it came for people to add tips to the bill. Ultimately, he said, management decided to keep it as a backup.
"It's a good piece of software, even though it has some things to be worked out," Choi said. "For relatively simple operations, we were really happy. The fees are actually really reasonable."
Williams, who recently moved her shop from First Avenue N to 2030 Central Ave., accepted only cash or checks at her old location. Spending a few hundred bucks on a credit card machine and then more on a merchant account wasn't feasible, she said.
She's already seen a boost in sales. Besides, she said, customers get a kick out of it, too.
"It's so easy. Even my mom can do it," she said. "I think it's just the way of the future."
Times staff photographer Leah Millis contributed to this report. Kameel Stanley can be reached at email@example.com or (727) 893-8643.