Few objects are as reliable as a fresh bar of soap. When we stand in our showers and lather our bodies we are doing something that our ancestors have done for more than 4,000 years—though unlike them, we tend to do it alone. The history of public bathing is important to Karen Kim, founder of soapmaker Binu Binu. Kim makes natural soap in the tradition of the jjimjilbang—Korean bathhouses that promote intergenerational bonding and simple good health. Unlike the Japanese onsen or Turkish hammam, the jjimjilbang is no place to laze around. One goes there to get clean, plain and simple, perhaps with the vigorous body scrub known as seshin. “It’s less about luxuriating or pampering, and more simply pragmatic,” Kim says. Kinfolk contributing editor Leonard Koren, founder of Wet maga...