1. Why do loose threads sticking out of clothes have color?
Sometimes, loose threads stick out from the hem or collar of a garment. If you pinch one, it might be the same color as the clothing, or it might look whitish. Textiles can be made in two main ways: dyeing the yarn before weaving, or weaving white yarn into cloth and dyeing it afterward. In this note, the first method is called "yarn dyeing" and the second is called "piece dyeing" [1]. In Tokamachi, Niigata Prefecture, many plant-fiber textiles such as Echigo-jofu are explained as being made by dyeing the yarn before weaving it. When threads of different colors cross each other on a loom, patterns like checks are formed [3]. But if you weave with threads of the same color, does the fabric look exactly like the thread?
2. Why does woven silk fabric look darker than the same-colored thread?
The Ibaraki Prefectural Industrial Technology Center compared the color of silk yarn samples from Yuki-tsumugi with the color of the woven fabric. When the warp (vertical) and weft (horizontal) threads were the same color, the brightness and vividness of the fabric were lower than that of either thread alone. The fabric looked darker and duller than the yarn [2]. This report calls the yarn-dyed Yuki-tsumugi a "mixed color" fabric, created by combining warp and weft colors. It states that this combination allows for complex, subtle colors that differ from piece-dyed fabrics [2]. Therefore, to create fabric of the intended color, the thread color must be slightly adjusted before weaving. However, this result comes from an experiment using Yuki-tsumugi silk yarn. It is not written as a rule that applies to all textiles. So, does piece dyeing avoid this difficulty? Before answering, let us look at a common example of piece dyeing.
3. How are patterns added to white silk cloth after weaving?
The same Tokamachi material explains that many modern silk textiles create patterns using the Yuzen technique after weaving. First, an artisan applies paste to areas of the white silk cloth where they do not want dye to soak in. Then, when dye is applied over the top, the pasted areas remain white [3]. A checkered pattern made from dyed yarn is born from the weaving action itself. Yuzen places patterns onto the finished cloth, almost like drawing with a brush. The methods of creating patterns are opposite. However, it is wrong to assume "plant fibers are yarn-dyed, and silk is piece-dyed." As mentioned, Yuki-tsumugi is silk but is yarn-dyed [2]. Even with the same material, the order is chosen based on the desired pattern and color method. When piece dyeing, the woven cloth is not dyed immediately. Pre-treatment steps are required. The Kyoto City Industrial Research Institute lists processes such as removing paste, scouring, and bleaching [7]. Yarn dyeing has labor costs for the thread, while piece dyeing has labor costs for the cloth.
4. Why does denim show white parts as it is worn?
Denim is a thick cotton cloth woven in a twill pattern. It uses dyed yarn (indigo) for the warp and bleached yarn (undyed whitish yarn) for the weft [5]. Because more indigo warp threads appear on the front and more white weft threads appear on the back, the inside looks whitish. Furthermore, product descriptions and articles explain that denim warp threads are often dyed in rope form. In these descriptions, the core of the thread is said to remain white [6]. As the denim is worn, the surface indigo fades, and these white cores become visible. However, this explanation comes from product introductions. Not all denim is rope-dyed, and this has not yet been confirmed in official public documents. With yarn dyeing, the color of the thread after dyeing and the look of the fabric after weaving must be predicted before making. What happens if there is any unevenness in the color of the dyed thread?
Note: In yarn-dyed textiles, the way thread colors are used is one example of how they can create different front and back appearances.
5. How do small differences in thread color create stripes in cloth?
The Ibaraki Prefectural Industrial Technology Center investigated the causes of horizontal stripes (yoko-dan) appearing in Yuki-tsumugi. Depending on the quality of the yarn, color differences can occur between bundles, or even within the same bundle, after dyeing [4]. Since color differences in yarn arise at each stage and are considered the main cause of these stripes, researchers wove test fabrics using yarn with intentional color differences to see how they affected the cloth [4]. In yarn dyeing, where each dyed thread is woven individually, shifts in thread color may appear directly in the look of the fabric. However, this study focused on hand-spun Yuki-tsumugi. The report does not compare whether this happens in piece dyeing. Still, it conveys the skill and dedication of artisans in creating threads with uniform colors.
6. How can you check whether your clothes were dyed as thread or as cloth?
Today, you can look at the inside of your clothes or the frayed ends of seams. If the frayed thread is the same color as the surface, it might be yarn-dyed cloth. If the thread is whitish and only the surface has color, it might be piece-dyed. However, there are exceptions to these signs, so do not assume. Do not pull threads out or cut the clothing. When you go out, look for displays in textile museums or workshops in production areas. There may be introductions to scenes of dyeing yarn or dyeing finished cloth. Official information, such as research reports from the Ibaraki Prefectural Industrial Technology Center and the multilingual explanation database from the Ministry of Land, Infrastructure, Transport and Tourism, can be found through the source links.