Silk Thread

Definition and Material

Silk yarn is a natural-fiber yarn made from silk obtained from silkworm cocoons. Because the fiber surface is relatively smooth, it has a distinctive luster that softly reflects light and a supple hand. It is used not only for apparel but also for embroidery and Japanese clothing-related applications.

Even when made from the same silk raw material, filament yarn that makes use of long fibers and spun yarn made by spinning short fibers differ in appearance and hand feel. In general, filament yarn is more likely to have luster and smoothness, while spun yarn has a somewhat more subdued appearance.

Twist and Yarn Structure

Silk yarn is made in structures such as single yarn, which uses one yarn, and plied yarn, such as two-ply or multiple-ply yarn, in which multiple single yarns are twisted together. Twist affects yarn strength, surface appearance, and sewability; yarn with more twist generally has a firmer look, while yarn with less twist more easily brings out a soft luster.

When used as sewing thread, the required thickness, twist, and luster are selected depending on whether the thread will be visible as stitching on the garment surface or used for seaming inside the seam allowance. In machine sewing, not only the thread structure but also compatibility with the needle and sewing speed affect the final result.

How Thickness Is Expressed

The thickness of silk yarn may be indicated by count or nominal count. Count is a unit that expresses yarn thickness, but the numerical meaning differs depending on the display system used. For that reason, numbers alone cannot be simply compared with other types of yarn or yarn using a different system.

Nominal count may be used as a thickness category set for each product. Even with the same nominal count, thickness and strength may differ depending on yarn structure, number of twists, and the manufacturer's standards. Before ordering or mass production, check the display unit, yarn sample, and actual sewing sample together.

• Check the count display system and the structure, such as single yarn or plied yarn.
• If you do not want the seam to stand out, choose a thickness and color that blend with the textile.
• When showing stitching as a design element, confirm the thickness and how the luster appears through test sewing.

Main Applications

Silk yarn is used for sewing silk textile, hand sewing, button attachment, embroidery, and more. In particular, it is chosen for formal wear, dresses, blouses, Japanese clothing items, and fashion accessories that place importance on luster and a delicate texture, in order to match the texture of the outer fabric.

However, caution is needed when the use area is subject to strong friction or a large load. Depending on the textile material, weave or knit structure, thickness, and wearing conditions, strength and durability should be considered, including sewing thread other than silk yarn.

How to Choose and Sewing Considerations

When selecting, in addition to color tone, luster, and thickness relative to the outer fabric, confirm the strength required for the seam and the washing or dry-cleaning conditions. Since silk, a natural material, may be affected by friction, sweat, chemicals, sunlight, and other factors, preliminary testing suited to the intended product use is important.

In machine sewing, adjust needle size, needle point shape, upper and lower thread tension, and sewing speed to prevent thread breakage, skipped stitches, and puckering. On thin or delicate silk textile, seam puckering is more noticeable, so test sewing should be done on scraps.

Compared with synthetic fiber yarns such as polyester yarn, silk yarn differs in luster, moisture absorption, weather resistance, and response to heat. In addition, some embroidery thread is intended mainly for decoration, and because the required strength and processing differ from machine sewing thread used for seaming, select according to the application.

Frequently Asked Questions