Washing/Milling in knitwear production

How’s everyone enjoying the knitwear season? Last weekend, I had the chance to visit the Tokyo Art Book Fair—it was such an inspiring event!

Today, I’d like to talk about the washing process used in finishing knitwear. After production, most knitwear undergoes a wash treatment to remove oils and dust from the factory, enhancing the fabric’s final texture.

In Japan we refer to this process as 縮絨 which directly translates to Milling.　

Milling is categorized into three levels; light, regular, heavy milling.

Light Milling

Light milling is recommended for wool, silk, cashmere, and rayon. This treatment increases volume and softness. By adjusting the length or frequency of washes, you can achieve a variety of finishes. Minor tweaks are made depending on the type of yarn used.

Regular Milling

Regular milling works best for wool, cashmere, alpaca, and other animal-based yarns. During the spinning process, these fibers accumulate oils, which are removed with detergents during milling. Afterward, the fabrics become softer and gain more volume.

For any after-treatments, such as brushing or printing, milling is always completed beforehand to ensure optimal results.

Heavy Milling

Heavy milling involves extending the washing time to the point where fibers tangle and felt. Wool fibers, like human hair, have scales that interlock under friction during a strong wash. This creates a denser, felted texture, increasing the fabric’s volume.

This process is not suitable for all yarns and is typically reserved for unshrunk wool.

Requirements for heavy milling:

• lengthen washing time.
• increase water pressure during wash for more friction
• increase water temperature
• increased temperature for tumble dry

However, heavy milling comes with challenges. Knitted edges lose their sharpness, so fully-fashioned pieces may not maintain their precision. For such fabrics, cutting and sewing are often more practical.

Even slight variations, like a 5-minute difference in washing time or temperature, can lead to uneven finishes. For this reason, professional treatment is essential when producing high-quality knitwear.

Over-milling can significantly alter the texture and feel of the fabric, so careful control is key.

In Japan, there are specialized companies with extensive experience in handling a wide range of yarns and fabrics. We collaborate closely with these experts to achieve the best possible textures for our yarns.

Additional Common Treatments:

• 湯通し　Warm-water wash
• ソーピング Detergent wash
• 柔軟ソーピング A rinse of Softener after wash）

Contact us or check our Yarn search for the recipe for our yarns. Treatments can make or break our beautiful yarns!