In order to provide stays of the finest quality and comfort, Zentis Osaka is very particular about everything hotel guests come in contact with, from interior design to the selection of fabrics and amenities.

Take, for example, the detergent used in Room 001’s self-service laundry, specially made by Kimura Soap, a long-established Osaka soap maker. Paying a visit to the Kimura Soap Factory located in the city of Yao about a 30-minute drive northeast from the hotel, we were given a tour around the site where the company manufactures its soaps with time-honored traditional processes.

Kettle-Cooking: A Process Maintained Since 1924

What we call, in a word, “soap” incorporates a wide range of products. Generally speaking, the first thing to come to mind for many people might be the familiar product used to wash the face and body, but there are also cleaning agents meant for general cleaning, laundry, the kitchen and more that fall into the category of soap as well.
These cleaning agents can be broadly divided into soaps and synthetic detergents. Synthetic detergents are made with chemically synthesized surfactants, starting with ingredients including oils and plant matter. Soaps, on the other hand, are made by mixing natural fats / oils or fatty acids with alkali to produce a reaction.

Kimura Soap is a company that chiefly produces cleaning agents for commercial use, which it supplies to facilities such as factories and public bathhouses, and cleaning agents, laundry detergents among others for home use. A pure soap component the company produces itself forms the basis of all these products. Moreover, Kimura Soap still uses the same manual kettle-cooking process they have relied on since their establishment in 1924, a tradition maintained by very few companies in all of Japan today.

A Craftsman Guided by Years of Experience and Intuition

There are two main types of kettle-cooked soaps: a powdered form and a liquid form. On this visit we decided to have a look at the kettle-cooking process for the liquid soap that forms the base ingredient for the liquid laundry detergent used in Room 001’s self-service laundry at Zentis Osaka.

Kimura Soap’s process for making liquid soap involves heating natural coconut oil and caustic potash while stirring them together to produce a saponification reaction.
The kettle is first filled with water, then caustic potash is put in, food-grade coconut oil is added, and the mixture is brought to a simmer.

The initially smooth-surfaced liquid in the kettle starts to froth and foam as the saponification process gets underway. A craftsman stands constant watch over the kettle from 8 o’clock in the morning until 3 in the afternoon, adjusting the temperature to keep the contents from overheating, pointing an electric fan toward the surface to keep the mixture from bubbling over, and so forth.

The craftsman must make full use of all five senses, as the saponification can be subtly affected by a wide range of factors, including climatic conditions, the air temperature and the level of humidity. Since the coconut oil in the mixture is food-grade — an ingredient sometimes used in making chocolate as well — they may even test the strength of the alkali by taste and adjust accordingly.

The timing at which to stop the simmering process is assessed by the craftsman’s eye as well. An hour after the heat is turned off, the bubbly foam will disappear, and the mixture is given a full day to gradually and thoroughly cool.

Soaps Gentle on People, Goods and the Environment

The soap is highly biodegradable, so its level of environmental impact is considered low. With its gentle degreasing power, the laundry soap brings out a lovely fluffy feel in clothes without making them starchy or stiff. Leaving virtually no residue on clothes fibers, it is safe to use for babies and those with sensitive skin as well.

In 2015, Kimura Soap launched the SOMALI body & home care series, offering products made from pure soap and natural ingredients. As the washing machines in Room 001 at Zentis Osaka dispense detergent automatically, the liquid laundry soap and clothing rinse used feature special formulation to be extra soluble in order to ensure compatibility with the automatic dispensation.

Be sure to experience the soft, fluffy feel of clothes freshly laundered with this soap during your stay.

Information as of October 2021.