1. What information is written on the composition label inside a skirt?
The tag on the inside of a skirt lists the fiber composition of the fabric. This is called the composition label. According to the Consumer Affairs Agency, this label must list the name of every fiber used, along with the percentage of each [8]. For example, a label might read "polyester 65% · cotton 35%," showing that two types of fibers are mixed together. This specific number combination is just an example, but this is the format used. The percentages show the proportion of each fiber in the fabric [8]. Polyester is listed as a fiber used for clothing and pleated skirts [1]. This raises a question: what exactly is polyester?
2. How is polyester made from PET resin, and how much is produced worldwide?
According to the Japan Chemical Fiber Association, polyester is made from PET resin, which is the same plastic used for PET bottles. The resin is heated until it melts, pushed out through a nozzle with small holes, and then cooled to form fibers. This process is called melt spinning [3]. Polyester is one of the three major synthetic fibers, along with nylon and acrylic, and it has the highest production volume among chemical fibers in the world [3].
Looking at the numbers, how much is it? Reports state that global fiber production in 2023 reached a record high of about 124 million tons (later revised to about 125 million tons). Of this, polyester made up 57%, while cotton was about 24.4 million tons [4]. In 2024, production rose to 132 million tons. Polyester accounted for 59%, while cotton dropped from 20% to 19% [5]. If we calculate 57% of 124 million tons, polyester accounts for roughly 70 million tons. This is nearly three times the amount of cotton. However, these figures include all fibers, not just those used in clothing, so they do not show the percentage for skirts alone.
3. How does heat make pleats in polyester?
Polyester has a property called thermoplasticity. This means that when heat is applied, the shape changes, and when it cools, it hardens in that shape. Pleats are created using this property [6]. The fabric is folded, heated, and then cooled, which sets the fold in place.
Some research reports note that even a household steam iron can set a crease neatly if pressure is applied and held until it cools [6]. However, this information comes from a paper summary, so specific conditions cannot be detailed here.
Another advantage is listed in the Encyclopedia Nipponica. It states that polyester is strong against friction, resists wrinkles, and is the most heat-resistant among synthetic fibers. Uses include clothing, shirts, and pleated skirts [1]. Heat creates the pleats, but it can also remove them. A product page for a 100% polyester pleated skirt shows care labels with examples such as weak washing up to 40°C, no tumble drying, and no ironing [7]. It makes sense to think that pleats set by heat might change if exposed to strong heat. However, this is just one example from one product and is not a rule for all skirts.
4. What roles do cotton, wool, and linings play in clothing?
According to the Encyclopedia Nipponica, cotton is strong, absorbs moisture well, has high heat resistance, and is easy to dye. It is used for clothing and underwear. Wool stretches well, is elastic, absorbs moisture, and is used for clothing and sweaters [1]. In contrast, polyester is described as having low moisture absorption [1][2]. Since the sources used here do not provide specific moisture absorption values for cotton or wool, we cannot compare them with numbers.
Linings use different materials. The same table notes that rayon is used for linings, and cupro is thin with an elegant luster, used for underwear, clothing, and linings [1]. Each fiber has different characteristics and uses. The percentages on the tag represent this mix.
5. When did polyester production start in Japan?
According to dictionaries, polyester was developed in 1941 by Winfield and Dickson in the UK. In Japan, Toray and Teijin introduced technology from the UK company ICI and began production successively starting in 1958 [2]. Because sources differ on whether industrialization in Japan began in 1950 or 1953, we stick to the explanation that production started in 1958. In 1970, polyester surpassed nylon to become the top synthetic fiber by production volume [2].
Where are clothes sold in Japan made now? A report citing a survey by the Japan Textile Importers Association states that in 2025, the domestic production ratio for clothing supplied in Japan was 1.1% by quantity. The supply volume was about 3.73 billion items, a record low [9]. Out of 100 items, about 1 is made in Japan. This figure covers all clothing, not just skirts. It is also unclear from this number whether the fabric of domestic products is also made domestically.
6. How can you read the composition label on your own skirt?
Find the tag on the inside of a skirt or trousers at home. Write down the fiber names and the percentage numbers in a notebook. Besides polyester, cotton, and wool, what else do you find? If there are two or more numbers, add them all up. Since the rule is to list the percentage for every fiber [8], the total should be close to 100.
Next, look at the laundry symbols. If there is an "X" on the iron symbol, it might be a clue that the material is sensitive to heat or that there are heat-set pleats. However, the reason for "no ironing" varies by product, so do not assume the reason. For more information, you can read the Japan Chemical Fiber Association's page on "Types of Chemical Fibers" [3] and the Consumer Affairs Agency's explanation of composition labels [8] in Japanese.