Why dryer compatibility? Once, during a town day after a rather long hike in New Zealand, the hostel I was staying at only had washing machines with an integrated dryer, and it shrunk my Merino wool clothes. Perhaps some of you may have had a similar experience. At that moment, I thought that I never want to experience the sadness of holding a shrunken Merino wool shirt in my hands while traveling again.

After many prototypes and a lot of trial and error, we were finally able to produce a fabric with little change in dimension even when subjected to a low-temperature dryer. The shirt made of thicker fabric is more durable, and reliable when traveling. I’m sure it will keep you comfortable in the mountains, where the temperature changes dramatically.

However, I have to admit that it no longer has the lightness of the previous light Merino. When I sweat a lot and my clothes get soaked, they are more stiff and harder to dry than before. Also, it feels a little hot to go around low mountains in the warm season. Another problem is that when I wash them with a lot of other clothes and dry them in the dryer, the fabrics tend to get tangled and wrinkled.

These are the problems that exist with Merino wool in general, and to some extent, these problems can be solved by adding synthetic fibers. Considering the excellent advantages of Merino wool, should we just ignore these problems, or should we continue our research and development to somehow solve them? I haven’t come up with the perfect answer, but that’s what the journey of making things is.

In the course of our research into base layers, we have realized the advantages of Merino wool and, more recently, synthetic fibers. Both have their advantages and disadvantages, and they differ greatly depending on the situation, application, and season. To create more products that meet different specific functions, Yamatomichi is also developing base layers that use some synthetic fibers. The reason I added “100%” to the name this time is that I wanted to differentiate it from the synthetic fiber blends that we will be producing in the future, and I also wanted to express my commitment to pure Merino even though it is not perfect with some drawbacks. In other words, I love 100% Merino wool so much, but it also has its disadvantages because it’s made of pure Merino.

In the beginning of the previous Product Story, I expressed my love for 100% pure Merino;

I really love Merino fabrics.

Deep in the mountains, as I walk, run, sweat, sleep, wake up and walk again, Merino wool is always my choice. For me, it connects my body with nature, and that is why I continue to focus on items made of pure Merino wool without any added synthetic fibers.

My love for 100% Merino Wool has not changed.

To conclude, I would like to introduce Rin Matsumoto, our textile researcher at Yamatomichi Lab and her contributions for the development of the fabric. Our journey to create is yet to end. (July 2021)

Development of 100% Merino Light

Rin Matsumoto (Yamatomichi Lab)

Here in Yamatomichi Lab, numerous tests and verifications have been conducted to develop the new 100% Merino Light fabric.

Our conventional fabric, Yamatomichi Light Merino, featured lightness, softness, and natural comfort. In addition, “ply yarn”, the method of twisting two yarns together, achieved the equivalent strength (tensile strength) to that of synthetic fiber fabric, as shown on the product webpage. On the other hand, as it gained much popularity, we realized the several challenges to deal with; relatively weak washing resistance, tendency to shrink, and occasional thread breakage. So the next goal was to develop a Merino wool fabric that endures repeated washing and a little rough handling.

To update the fabric we had a series of discussions with the development and production team of Bishu, the production area of wool garments in Japan, where our Merino fabric is being produced. Bishu is one of the world’s leading wool textile production areas, in which professionals from spinning companies, fabric factories, dyeing and processing factories, and inspection organizations are all located. Each of them brought their specialized knowledge and ideas to the development process.

As we analyzed and compared the many prototypes we had made as well as the Merino products released by other companies, we paid fresh attention to the New Zealand Merino fabric that Yamatomichi had once used in the past. The quality of the past fabric was stable, with no degradation of the fabric even after several years of wear by our staff and customers, no holes due to thread breakage, and no stretching out of the ribbing around the neck, cuffs, and hem, and we highly evaluated its perfection, balance, and toughness. We, therefore, conducted another analysis of yarn count and knitting density to understand why it was so good in quality.

Our analysis discovered that the NZ Merino wool fabric we once adopted was made of the “single yarns”. Each “single yarn” and “ply yarn” has its characteristics, and the right choice differs depending on the priority.

The previous Light Merino used “ply yarn” because we focused on durability (tensile strength). For the development of this new material, on the other hand, we chose “single yarn” based on the New Zealand Merino wool fabric standard.

The “ply yarn” is a combination of two strands of wool twisted together. Natural fiber yarns have thick and thin sections that are unevenly distributed when viewed under magnification, and for this reason, there are sometimes weak spots in the yarns when the weak section of two strands are twisted and overlapped, consequently causing yarn breakage. Although the thickness of the single yarn is usually uneven in some places, we improved the twisting process to make the thickness of the yarn as even as possible, thereby stabilizing the quality.

Another major challenge was to minimize shrinkage due to washing and to make the product machine-dryable. Most Merino wool products on the market are labeled to avoid the use of the dryer. When we tumble dry other companies’ Merino wool products, they shrunk so much that their size changed, and we realized once again that it is a difficult task to make them dryer-safe.

The texture of the initial prototype delivered from Bishu was stiff and not as soft and comfortable as the previous Light Merino fabric. In terms of shrinkage after washing, it was milder than the previous fabric, but there was still room for improvement. After the dryer, the previous fabric deformed and significantly shrunk, but the prototype did not show any change in appearance after the dryer, and the texture became softer and puffier. It was more comfortable to wear than the previous fabric, which seemed to be a big step forward to success. As for the shrinkage, when the fabric was machine-dried for the first time, it shrank to a certain extent, but once it shrank, it did not shrink further even after dried repeatedly.

I shared these results with the development team in Bishu, and we decided to add a tumble drying step in the production process. By incorporating this process, a process not normally done in wool knits, the fabric should become soft, and tighten, stabilizing the shrinking. To maximize the effects, The team conducted the process without focusing on production efficiency, and made specialized adjustments and innovations. Also, the garments were put into the tumble dryer wet instead of dry, and the timer was set longer than usual.

The results were as I predicted. The fabric became soft and the rate of shrinking stabilized. There was no change in shape even after putting the garment through a low temp tumble dryer.

Although pre-shrinking the garments stabilized variations in shape and size, It also made the knitting denser, increasing the weight more than expected. We thought about using finer yarns or reducing the knitting density to make the fabric lighter, but after some adjustments, we found a balance of where the fabric was dryer compatible and with mild shrinkage. Any changes would completely botch the balance and we would be forced to start all over.

We then compared the newly developed Merino wool with the previous version. The new Merino wool is heavier and the tensile strength is slightly lower due to the change from ply yarn to single yarn. The knit is tighter, which reduces air permeability but increases insulation. The old Merino is lighter and more breathable, so it may be more comfortable in the summer or during low altitude hikes in the warmer months. On the other hand, the newly developed Merino will retain heat better, and is better suited for the colder months and high altitude hikes in the summer, when temperatures can vary drastically between day and night. It is in this environment that you should experience the natural moisture conditioning capabilities of Merino wool. Furthermore, it shrinks less when washed and can be put in the dryer.

To guarantee dryer compatibility, we made a prototype with the newly developed Merino wool and repeated 30 times of machine-washing and low-temperature drying at an inspection facility. The shrinkage rate was stable, the texture remained soft, and in fact, the fuzz seemed to settle, making it smooth to the touch. We also sent the test results and the prototype to a laundry expert, who also washed them to confirm our results. However, they also advised us that using the dryer too often may shorten the life of the product. In addition, during the testing process, we found out that when multiple loads of laundry were put in the dryer at the same time, the wrinkles became stronger. Long sleeves in particular tend to dry with the sleeves tangled together, resulting in wrinkles. The laundry expert advised us to dry the garments separately as much as possible to avoid wrinkles.

When we solve one problem, another problem surfaces, I think this is what developing gear is all about. Sure, we aim to create the perfect material, but it is difficult to create a fabric that is well-balanced in all aspects. A material that is well-balanced in all aspects will make the cut, but will lack uniqueness and won’t have any explicit perks.

Among fabrics, wool, a natural fiber, is not something that can be mass-produced in the same way as electrical appliances or plastic molding, and there are variations in the length and thickness of the fibers and the way they shrink. Even if a prototype is repeatedly tested and does well, we can’t expect the same results in mass-produced products, and unanticipated problems are bound to occur. There are times when we think that by blending synthetic fibers, production would be more predictable but I think we continue to stick to 100% Merino because we feel that it carries great value.

In parallel with the development of the Merino wool jersey fabric, we also revised the knitting. With knits, elasticity is important to endure repeated stretching, and so we were simultaneously working on a synthetic fiber blend, but we decided to proceed with 100% pure Merino knit.

After many prototypes, tests, verifications, and meetings, we finally came up with 100% Merino Light that could be put in the dryer. This is not the end goal, and there are still many issues to be resolved. The next development, the search of making even higher quality garments is already in the works.