In the early ’90s, artist, aesthetics expert, and writer Leonard Koren was bathing at a hot-springs resort near the Japanese city of Kamakura when he was struck by an idea for his next book. Observing his fellow bathers, Koren noticed that each one followed the same time-honored Japanese bathing procedure: Undress and wash the body with warm water; submerge in a tub (or pool) of hot water, enjoying the steam and warmth until the body is thoroughly heated; exit the tub and wash the body and scalp with soap and water; then enter the tub once more for a longer soak.

He resolved to create a step-by-step instruction manual detailing the ritual of the Japanese bath, a practice that is as much about cleansing one’s body as it is about purifying oneself mentally and spiritually. (Koren discussed the psychological benefits of bathing, as well as his recent memoir, Musings of a Curious Aesthete, on Ep. 78 of our At a Distance podcast.) By the time Koren was dressed and ready to leave the bathhouse, he had outlined the book’s entire format and pictorial scheme. Published in 1992, How to Take a Japanese Bath is a concise, 40-page guide to bathing for “hedonists, hot tubbers, and fans of stylish, understated graphic art.” Its twelve black-and-white drawings, by famed manga artist Suehiro Maruo, are decidedly G-rated (and a stark departure from his work’s characteristically dark imagery). They depict people rinsing, soaking, relaxing, and thinking, showing readers how to slow down through the calming ceremony of a bath.

The basic steps of taking a Japanese bath are practical in nature, the book explains, and are designed to facilitate full-body cleansing while conserving resources—water and electricity—and to ensure an equally pleasant experience for other bathers. A bath can take place at any time of day: in the morning soon after waking up, at night to calm the nerves before going to sleep, or at any other moment when inspiration strikes. (To add an olfactory element to the cleansing experience, we suggest bathing in a tub made of hinoki, a fragrant species of cypress native to central Japan.)

How To Take a Japanese Bath is just one element of Koren’s decades-long exploration of bathing. In 1976, two years after studying architecture at the University of California, Los Angeles, he founded WET, a quirky, avant-garde publication with the subtitle “The Magazine of Gourmet Bathing.” Through its five-year-run, WET helped define the Los Angeles new wave aesthetic and developed an international following for its combination of artwork and essays that used the subject of bathing as a vehicle to explore art, culture, and human behavior.

On the occasion of the book’s 30th anniversary, we recently spoke to Koren about what initially drew him to bathing culture, the spiritual side of washing oneself, and how the role of bathing has evolved in Japan.

How did your interest in bathing first take shape?

While in graduate architecture school I became interested in small, intimate environments. The Japanese teahouse seemed to fit the archetype perfectly. When I was an undergraduate at U.C.L.A., I discovered that the school actually owned a Japanese teahouse. A wealthy Bel Air couple had purchased it in Japan, had it disassembled, then reassembled it in their backyard, which, in the meantime, they had transformed into a Japanese garden with a koi pond. Eventually, they donated the entire property to U.C.L.A. But because Japanese gardens and teahouses are delicate, only special visitors were allowed to visit, and only at special times. Despite this, the director of the visitor center gave me permission to visit any time I wanted, because she knew of my interest in Japanese art and aesthetics.

Unfortunately, teahouses are elitist environments. That is, you either have to be rich or a dedicated Japanophile in order to have access to one. So I searched for a more democratic, small-intimate-environment archetype, and came to realize that the bathrooms in most peoples’ homes met all my criteria. Your bathroom may not be amazing or gorgeous. That doesn’t matter.

Nevertheless, toward the end of architecture school, I began documenting as many extraordinary bathing environments in L.A. that I could. My methodology was word-of-mouth and serendipity. On one particular bike ride to school, for example, I detoured through the Holmby Hills area and saw a man in a bathrobe picking up the morning newspaper in front of an art deco mansion. I pedaled up and asked if he had any interesting bathrooms in his house. “In fact, I do,” he replied. We chatted for a bit, and then he invited me inside. I was blown away. The bathrooms were mint-condition 1920s or 1930s art deco fantasia. They were gorgeous. Spectacular. I asked if I could come back and photograph them, and I did.

After graduating from architecture school, I wanted to begin making art again. The imagery and metaphoric richness of baths I had documented remained in my mind. So did dredged-up memories of bathing experiences I had had at Esalen, Tassajara, and at a bathhouse in New York that an uncle took me to when I was 9 years old. Bathing was an extraordinary thing that humans do, I thought. And when bathing occurs in beautiful, natural settings in pools of hot mineral water, it is an ultimate experience.

In the book, you mention that in Japan, bathing is about physical and spiritual cleanliness. How does that perspective play out in a broader cultural context?

In Japan, the interconnected notions of purity and cleanliness are deeply embedded in the culture. To be pure is to be clean, and to be clean is to be pure. When you enter a Japanese home, for example, the first thing you do is take off your shoes. You leave the dirt—the impurities of the outside world—in a transitional place just before entering the home proper. The home thus remains clean and pure.

Of course, in reality, this is delusional thinking: There is no absolute clean or absolute dirty. There is only relative clean and relative dirty. When you partake of the Japanese bathing ritual, however, it seems as if you are removing all the impurities that are clinging to your body. You are therefore making yourself pure again. After a Japanese bath, you do feel cleaner—emotionally lighter and cleaner.

But besides the cleanliness, purity, sanctity, lightness, and mental well-being, there is also the sensual pleasure of the bath. When it’s cold in the winter, a hot bath is a wonderful way to warm the body and soul. When I lived in Tokyo, from November through April I’d work in the morning. Then, around noon, when I felt cold, I’d take a bath.

Has the practice of bathing in Japan shifted over time?

In certain respects, it definitely has. In 1960, there were something like thirty thousand public baths in Tokyo. When I stopped living there, at the end of the nineties, that number was reduced by about two-thirds. The public bath as a place for establishing community disappeared when tubs and showers were built into new, individual apartments and houses.

For a while, I rented a room in an apaato—a type of old, wooden apartment building—for my office. Most of the renters in the building lived there full-time. The building had no bathing facilities, so the residents were forced to use the public baths, as Japanese people generally did in times past. As the country modernized and the need for public baths was greatly reduced, something of important cultural value vanished. It’s no surprise, then, that Japanese city-dwellers fantasize about the idea of going to hot-springs resorts, where communal bathing is still practiced.

And may be why people reach for bath salts and powders inspired by Japanese hot springs, or onsen, when a trip to one isn’t possible. Has your relationship with bathing changed since writing the book?

My relationship to everything has changed. Things that I enjoyed in one phase of my life haven’t necessarily moved forward with me. So yes, my personal views about bathing have changed, too.

About a year ago, my wife and I were looking to buy a larger apartment in the small Italian town where we were living. Simultaneously, I did research on what it would involve to install a Japanese bath in this new apartment. The Japan Foundation in Rome gave me a few leads to follow up on, but in the end, I realized it would be an inappropriate thing to do. The ostentation, the self-indulgence of a Japanese bath in Italy, felt all wrong—for me, anyway. On the other hand, my father-in-law has a beautiful old claw-foot tub in the middle of a rustic room in his studio workspace. One of these days I’m going to ask him if I can take a bath there. In the meantime, I take showers.