Introducing Chemical B: Yamatomichi’s New Synthetic Base Layer

(Currently only available in Japanese)

Through countless comparative tests, we confirmed merino’s strengths—its odor resistance, temperature control, and moisture regulation. But I also came to appreciate what synthetics offer, especially their breathability and quick-drying performance.

From there, a new idea began to take shape:

• A synthetic base layer that resists odor like wool
• Yet is lighter and more durable, addressing wool’s weaknesses

This became the starting point of the project.

We found that odor control and insulation are especially important for hiking, while moisture-wicking, dispersing, and quick-drying properties are crucial for trail running.

We also identified two main approaches to managing sweat effectively:

Ventilation type — uses lightweight fabrics with mesh or grid structures to maximize breathability and speed up evaporation.

Wicking type — pulls sweat quickly away from the skin, spreads it across the fabric surface, and keeps the inside dry.

In other words, an excellent base layer needs three things: odor control, insulation (which doesn’t necessarily mean warmth), and superior sweat management. Of these, sweat management is the critical factor for both hiking and trail running.

The first two years of development were slow. As someone deeply attached to merino wool, I found it difficult to discover a synthetic material I truly wanted to wear while hiking.

Things changed once we began working with Teijin Frontier. Their trial fabrics treated with EcoPure®—a yarn treatment that suppresses odor-causing bacteria—showed impressive odor-eliminating performance. That discovery gave the project real momentum and accelerated development.

With EcoPure® providing reliable odor control, we concluded that the wicking approach—keeping the skin consistently dry—delivers greater comfort. Mesh fabrics work well for hot-weather trail running, but we found them less effective in cases of heavy sweating or in Japan’s hot, humid climate, where drying simply can’t keep up.

We tested countless prototypes. The first hurdle was odor control, followed by sweat management, and then durability.

As a brand that has long championed the strengths of merino wool, Yamatomichi could not settle for a half-hearted synthetic base layer. Our goal was to create one that hikers would actively choose even over merino. With that conviction, we pressed forward with development.

After overcoming each challenge, the final step was validation. Because sweat and body odor differ from person to person, a meaningful test required a diverse group of users. For this prototype, we involved 14 participants—including staff and partners—the largest test group we had ever assembled.

The research that began with Yamatomichi Lab: Base Layer Edition finally came together after five years in the form of Chemical B.

Feedback was largely positive, but it also revealed how differently people perceive odor control. Some felt Chemical B’s deodorizing effect was very strong, while others noticed it less.

To explore this, we measured the acidity and alkalinity of over 100 sweat samples using litmus paper, yet no clear pattern emerged.

What we did learn is that Chemical B is particularly effective at suppressing the ammonia odor that occurs immediately after exercise. However, it is less effective against acidic odor compounds such as butyric acid and isovaleric acid, which are commonly associated with body odor. Since sweat composition and body chemistry vary from person to person, this likely explains the range of experiences—a mystery we are eager to continue investigating.

No matter how much data or how many test results we collect, what truly matters is how a product feels when you put it on and start moving.

For me, the real value of Chemical B isn’t only its odor control, but the comfort of its sweat management. Even when damp, it doesn’t cling to the skin or cause discomfort—and in this respect, I believe it even surpasses merino wool. On hot, demanding days, Chemical B is the base layer I instinctively reach for.