What is pure silk? An easy-to-understand guide to its differences from silk, characteristics, and how to identify it

1. What is Shoken (正絹)?

Shoken refers to threads or fabrics made of 100% silk.

Silk is a natural fiber obtained from the cocoons produced by silkworms. In Japan, it has been used for kimonos and obis since ancient times.

The great appeal of shoken is its elegant luster and supple, smooth texture, characteristic of natural fibers. Its appearance changes with how light hits it, beautifully showcasing delicate colors and patterns created by dyeing and weaving.

On the other hand, it is a material that can be affected by moisture and friction, so care must be taken in its handling.

2. What are the differences between Shoken, Kinu, and Silk?

While "shoken," "kinu," and "silk" are similar terms, organizing their meanings makes their differences clearer.

Kinu (絹) is the name of the natural fiber itself, obtained from silkworm cocoons. And Silk is the English word for "kinu," so generally, kinu and silk refer to the same material.

On the other hand, shoken (正絹) refers to something made of 100% silk, without mixing other types of fibers.

In summary, it's easy to understand if you remember that "Kinu = name of the material," "Silk = English name for kinu," and "Shoken = 100% kinu."

3. Characteristics and Appeal of Shoken

One of the appeals of shoken is its soft, deep luster. Its appearance subtly changes depending on the viewing angle and how light hits it, beautifully enhancing the colors and patterns of the kimono.

It is also characterized by its supple and smooth texture. Silk has moisture-absorbing and releasing properties, allowing it to easily regulate humidity within clothing.

In addition to the inherent beauty of the material itself, the combination with dyeing, weaving, embroidery, and other techniques allows each garment to showcase a variety of expressions, which is another charm of shoken kimonos.

4. How to Distinguish Shoken from Polyester | 7 Key Points

If a kimono still has its quality label, the basic step is to check the material display.

However, with old or vintage kimonos, the quality label or purchase information may be missing. In such cases, the following characteristics can serve as clues for identification.

① "Kinunari" when rubbing the fabric

One known method for distinguishing shoken is "kinunari" (絹鳴り).

When silk fabrics are gently rubbed against each other, a unique "squeak, squeak" sound or sensation may be produced. Polyester is less likely to produce the same sensation, making it a potential indicator.

However, the intensity of kinunari varies depending on the weave, processing, and condition of the fabric, so "no sound = not shoken" cannot be definitively concluded.

② Texture when touched by hand

Shoken is generally supple and smooth, yet can feel slightly resistant to the fingertips.

On the other hand, polyester tends to have a relatively uniform and slippery feel on the surface.

However, since there are now synthetic fibers that closely resemble silk in texture, it is not possible to conclusively identify shoken by touch alone.

③ Appearance of luster

Shoken tends to have a soft luster that changes depending on the direction of the light. When the fabric is slightly tilted under natural light, a deep luster can sometimes be observed.

On the other hand, polyester, depending on the product, can reflect light relatively uniformly, and its luster may appear strong.

However, the appearance changes depending on the weave and surface treatment, so this is also a supplementary factor for identification.

④ Wrinkles when grasped

The condition after lightly grasping and releasing the fabric, without damaging it, can also be a reference.

Since shoken is a natural fiber, creases or wrinkles may remain relatively easily. On the other hand, polyester generally tends to return to its original state more easily.

However, there are also differences depending on the thickness, weave, and processing method of the fabric.

⑤ Static electricity and clinging

Synthetic fibers such as polyester are prone to generating static electricity in dry environments, and the fabric may feel like it clings.

While shoken is not entirely free of static electricity, strong static electricity or clinging can be an indicator of the material.

⑥ Wearing comfort when sweating

Silk has hygroscopic properties, meaning it absorbs moisture from within clothing.

On the other hand, polyester generally has low hygroscopicity, so when sweating heavily, it may feel stuffy or cling to the skin.

However, this is not a specific test method for identifying materials, and wearing comfort also varies depending on the fabric thickness, weave, lining, and processing.

⑦ "Burn test" to check how the thread burns

One method of fiber identification is the "burn test."

Since silk is made of animal protein, when burned, it emits an odor similar to burning hair or feathers, and the residue tends to be black and easily crumble into ash when touched.

On the other hand, polyester melts while burning and, when cooled, tends to leave hard, bead-like residues.

5. To identify Shoken, look for multiple characteristics

When distinguishing shoken, it is important not to declare it "shoken" based on a single characteristic.

By comprehensively checking multiple characteristics such as kinunari, hand feel, luster, and wrinkles, you can gather more evidence for identification.

However, these are merely guidelines. If accurate determination is required, such as for material labeling at the time of sale, there are methods of fiber identification by experts or testing institutions.

6. Not all Kimonos are Shoken

While some may have the image that "kimono = shoken," not all kimonos are made of shoken.

In addition to silk, kimonos are made from various materials such as cotton, linen, wool, and polyester.

There are also kimonos made with "koshoku" (交織), which means they are woven by combining different types of threads.

For example, silk threads and cotton threads, or silk threads and wool threads, are combined to weave a single fabric. Therefore, even if a kimono uses silk, it is not necessarily "shoken = 100% silk."

Note that "koshoku" and "konbo" (混紡, blended) are strictly different. Koshoku refers to weaving by combining different types of threads, while konbo refers to mixing different types of fibers to create a single thread.

Especially with vintage kimonos, quality labels or purchase information may be missing. In such cases, caution is required when identifying a kimono as "shoken" or "Silk" based solely on appearance or feel.

On the other hand, the appeal of old kimonos is not determined solely by the material. The colors, patterns, weaves, and textures unique to items that have passed through many years also contribute to their distinct charm.

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