The day Karen Robinovitz was reintroduced to slime in 2018, she ran up to her New York apartment's rooftop with her friend's 10-year-old daughter and tried drizzling it all the way to the ground.

"It turned me into a 7-year-old for four hours," says Robinovitz, 52.

It was the first time she'd felt joy in a year and a half, she says. Within a nine-month span, her husband had died by suicide and her teenage cousin was killed in the Parkland high school shooting. Amid medications, support sessions and therapy, playing with slime offered Robinovitz some unexpected relief — so she bought a handful, then hundreds, of jars from TikTok creators.

She'd stumbled onto a niche industry: Some small businesses, particularly on TikTok, have reported bringing in more than $1 million per year making and selling stretchy, elastic goo that you can squish and pop in your hands. But Robinovitz, who ran a talent management agency for social media influencers, and her friend Sara Schiller, founder of an event space company, saw a chance to sell more than just slime.

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Today, they co-run The Sloomoo Institute, an interactive slime experience — a description they prefer to "museum" or "play space" — with locations in New York, Los Angeles, Atlanta, Chicago and Houston. After buying tickets, which average $34 per person, visitors are handed a gob of slime and invited to smack it against a wall. Inside, they'll find customizable slime stations, ASMR rooms and white fiberglass vats of slime with different textures and smells.

Sloomoo sells slime too, but about 85% of its revenue — up to $4.3 million per month last year, it says — comes from ticket sales. Its first four locations brought in $28.9 million in revenue in 2023, including $4.6 million in earnings before interest, taxes, depreciation and amortization (EBITDA), according to documents reviewed by CNBC Make It.

The company says its full-year earnings for 2024 aren't yet finalized.

"Karen and I [have] a deep belief that in tapping into your senses, you're creating an emotional connection," says Schiller, 54, adding that Sloomoo has been profitable since the day its first location opened. "That's so much more powerful than just mailing out packages of slime."

'Lines down the block' for slime

Sloomoo unofficially began at one of Robinovitz and Schiller's weekly get-togethers, at Schiller's loft in Manhattan's Soho neighborhood. Both women needed emotional relief: Schiller's husband suffered brain-damaging strokes a couple years prior, making her the family's sole caretaker.

Slime occupied their hands as they spoke: Such sensory-heavy activities can improve depression and anxiety symptoms, some studies show. Then, the pair watched Schiller's daughters, one of whom is nonverbal and has limited motor skills, handling the slime together — a rare way for the siblings to connect and play with each other.

The two friends bought more than 900 jars of slime to study, Schiller says, then worked on their own recipes. (Always start with Elmer's glue, Robinovitz says.) They attended conferences, where they met and hired slime creators, and raised $1 million from a private investor, the co-CEOs say.

They put $400,000 of their investment money aside — "If this flopped, we still had to pay rent," Schiller says — and put the other $600,000 into refurbishing a rental space near Schiller's home.

They invited slime, parenting and lifestyle influencers on hardhat tours mid-construction as a marketing strategy, Schiller says. Their grand opening in October 2019 sold out — 3,000 tickets — before the duo even opened their doors, they say.

"I remember this mother was crying to me, saying, 'My daughter has to come today, all her friends are here,' and I was like, 'I cannot sell you a ticket, we're at capacity,'" Robinvitz recalls. "But when I turned around, the little girl ran [in], threw off her shoes and jumped in the lake of slime."

"There were lines down the block," Schiller adds. "People weren't mad they were jostled in. They couldn't believe they had an opportunity to actually get in."

Debt, expansion and 'doing something that's never been done before'

In its first week, Sloomoo sold $1 million worth of tickets, Robinovitz and Schiller say. Five months in, the Covid-19 pandemic arrived and the business let go of roughly 90 part-time employees, keeping just the co-CEOs, a bookkeeper and their resident slime-maker.

They sold slime online, hosted virtual slime-making camps for kids, and hosted corporate workshops for companies like Google and Pfizer until fully reopening in 2021. The following year, Sloomoo raised $5.8 million in a Series A funding round led by Raptor Group, and opened its Chicago and Atlanta locations.

The company took on $5 million in debt from its investors to open in Houston in 2023 and Los Angeles last year, the co-CEOs say. They've paid the money back, and their future expansion plans include more locations, physical products, leaning programs, games and even live entertainment, they note.

The popularity of their central product, the slime itself, has ebbed and flowed over the decades — from the slippery, chemical-smelling slime of the 1970s to Nickelodeon's "Slime Time Live" in the early 2000s. Since today's TikTok-fueled slime popularity will probably fade eventually, Sloomoo's longevity is dependent on giving visitors memorable, unique experiences, says experience economy researcher, consultant and author Joe Pine.

Experience-based businesses are successful when they're memorable, meaningful, create a sense of awe and, most elusively, change who we are, says Pine. Interactive art exhibition company Meow Wolf and Italian food market chain Eataly, for example, check all four boxes, he says.

Sloomoo's vats, walls and lakes of scented slime fulfill the first three, Pine notes. He's not 100% sold on Sloomoo's ability to transform people — but Schiller and Robinovitz say it's certainly changed the two of them, at the very least.

"Karen and I could be SVPs at major companies, and we've chosen to do this because it's really meaningful to us," Schiller says. "We want people to know that you can choose to try, get out there and do something that's never been done before."

"After what we've both been through, what are we going to be afraid of now?" she adds.

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