A dozen women sat around a table at Little Shop of Crafts on the Upper West Side of Manhattan listening attentively and taking detailed notes as Marla Bosworth gave them the skinny on soap-making.

Over the course of the three-hour workshop on a recent Friday evening, Ms. Bosworth, the founder of Back Porch Soap Company, emphasized the vigilance that’s required when working with sodium hydroxide, better known as lye, a key ingredient in soap. She inveighed against the use of palm oil because of its environmental impact (“I’m going to get on my soap box here for a minute,” she said); likened formulating a soap recipe to building a house; and encouraged creativity.

“You can use anything in your spice cabinet for fragrance,” said Ms. Bosworth, whose fee ($168 per student) included hands-on soap-making from scratch, in this instance whipping up two batches of shea-butter soaps scented with essential oil blends: one with lavender, the other lemongrass.

Tools included an immersion stick blender, a scale, a plastic mixing spoon and a large stainless-steel pot. At the end of the class, everyone went home with some soap and a reminder to let it dry out for four weeks before working up a lather.

“There’s nothing like making your own soap — I love the alchemy of it,” Ms. Bosworth, 52, told her students.

Those students were all hoping for another sort of alchemy: turning their growing skills into a successful business. But they’ll be joining a crowd.

What was a tedious, housewifely chore before the introduction of commercial bar soap has become a hugely popular artisanal endeavor. The term “handmade soap” pulls up more than 76,000 results on Etsy. There are 300,000 soap-making businesses in the United States, according to Leigh O’Donnell, the executive director of the Handcrafted Soap & Cosmetic Guild, a nonprofit trade association. And, she added, “the number is growing.”

Part of what’s helping fuel that growth is soap’s status as a recession-proof indulgence. Whatever the economy, “people are willing to buy that nice-smelling bar for $6 or $8 at the farmers market,” Ms. O’Donnell said.

Further, soap makers — 95 percent of whom are women — view the blending of alkali and oils as something they can do at home to supplement the family income.

“Some are happy staying small, but some are very entrepreneurial and want to have a lot of stores,” Ms. O’Donnell said.

Since soap doesn’t require premarket approval from the Food and Drug Administration — as long as it’s labeled, sold and represented solely as soap — the barriers to entry are low.

As is the price of getting into business. “You can get started for under $50,” said Ms. Bosworth (presuming that you don’t pay for her class).

Soap-making is a relatively simple process as long as you have patience and a precise scale. But as with baking, some have the knack, and some don’t.

Even for people who are highly skilled, turning a big profit is a challenge. One lavender-infused bar smells pretty much like another after all, and removes dirt with equal dispatch.

“Soap is such a commodity,” said Ms. Bosworth, whose website describes her as an herbalist, aromatherapist and energy healer based near Boulder, Colo. “You can find handmade soap anywhere.”

But 19 years ago, when she was starting her business in Massachusetts, there were only four other indie soap makers in the state, she said, and just a few thousand in the country.

When the economy tanked in 2008, “I had a lot of competition all of a sudden,” Ms. Bosworth continued. “It forced all of us to differentiate ourselves.”

For a time, “organic” and “goat milk” were useful terms for soap makers who were understandably eager to set themselves apart from the rest of the competition. “But then someone else would have goats’ milk, and you’d have to come up with something else to make you even more special,” said Ms. Bosworth, whose response, for a time, was to offer sea-inspired soap, like seaweed and sea salt.

Now her company offers 10 varieties of soap, all of which she still makes personally. She charges $8 for a six-ounce bar, but declined to say how many she sells a year.

Some soap-sellers get started in the business because they live on farms and have an abundance of goats’ milk that might otherwise go to waste. Such was the case with Elizabeth Sanders, 33, a soap maker based in Winston-Salem, N.C., whose nine-year-old company, Horse ‘O Peace, sells 17 kinds of raw goats’ milk soap bars, scented and unscented. Five dollars and 50 cents will get you a four-and-a-half-ounce bar through the company’s website and on Amazon.

An average order is six to eight bars, though some customers buy as many as 30 decidedly unpretentious bars a year. “Our soaps are all naturally beige,” Ms. Sanders said. “We’re not trying to beautify with dyes and make it look unnatural.”

A background in crafts is common. Susan Ryhanen, the founder of the company Saipua, once made wooden garden ornaments. Now, she makes soaps like saltwater and rose geranium in a home studio in Yorktown, N.Y. Hand-wrapped in decorative papers imported from Italy and Nepal, the bars, $18 each, look like gifts.

Others in the business begin tinkering with lye and oils to address a family member’s skin condition or as a way to avoid the artificial ingredients in commercial products.

PJ Jonas, the owner of Goat Milk Stuff in Scottsburg, Ind., had several of her eight children in the bathtub one night nine years ago “and I was letting them splash around,” she recalled. “Then I looked at the what was in the soap, and I couldn’t believe I was putting it on their skin,” Ms. Jonas, 44, said. “I wanted to get more natural. We lived on a farm and had the goats’ milk, so I learned to make soap.”

When her husband tried it and his skin stopped cracking, that was sufficient impetus for Ms. Jonas to start selling, as her website puts it, “a good, clean soap made by a good, clean family.” Goat Milk Stuff now sells several hundred thousand bars of soap a year, said Ms. Jonas, who has turned the soap-making chores over to her 18-year-old son, Colter.

For some companies, soap ultimately becomes a loss leader. “I make money off my soaps, but it’s labor-intensive,” Ms. Bosworth said. “Soap will bring the customers in, but it can be the gateway to selling the higher markup and less labor-intensive lotions and serums and lip balms.”

Horse ‘O Peace, for example, offers lip balms and moisturizers, and recently introduced a line of pet care products. Goat Milk Stuff’s product line includes laundry soap, liquid soap, lotions, cheese, yogurt, milk, gelato and fudge.

Fortunately for soap makers, consumers seem to appreciate their back-to-basics ethos. “I think that when people start using it, they realize this soap is different from commercial soap,” said Ms. Ryhanen of Saipua.

More than that, they buy into the art of the well-made bar. “You get up in the morning, and the smell of the coffee brewing and the smell of the soap in the shower are aromatherapy,” Ms. Bosworth said. “It’s more than just a bar of soap. It’s something that sets the tone for the whole day.”