Knit Interfacing

Definition and Overview

Knit interfacing is an interfacing widely used as fusible interlining, with adhesive resin applied to a knitted base fabric. Because of its knitted structure, it is softer than woven interfacing and more easily follows the movement of stretch fabrics.

Tricot interfacing is sometimes treated as another name for knit interfacing. Tricot is a type of warp knit, and in practice it usually refers to knit interfacing made with a tricot-knitted base fabric.

Areas of Use and Role

It is mainly used in areas where shape needs to be maintained or stretch needs to be controlled, such as collars, collar stands, front plackets, cuffs, facings, pocket openings, and the waist area. It reinforces areas that are not strong enough on the outer fabric alone and helps stabilize the appearance after sewing.

For cut-and-sew items and thin knit materials, it is important that the interfacing does not interfere with the stretch of the outer fabric. By applying the appropriate knit interfacing only to the necessary areas, it is easier to reduce pulling during wear and excessive stiffness.

Materials and Types

The base fabric is often made from synthetic fibers such as polyester, and stretch, resiliency, and hardness after bonding vary depending on the knitting method, thickness, industry weight, type of adhesive resin, and coating condition. The direction in which it stretches also differs by product number.

Adhesive resin may be arranged in dot patterns and similar forms, which affects adhesion to the outer fabric and the hand feel. Depending on the application, it is selected with consideration for the bonded condition after washing or cleaning.

• For thin fabrics: A type that is less likely to affect the fabric's hand feel and drape.
• For medium-weight to heavy fabrics: Used when stronger shape retention is needed for collars, front edges, and similar areas.
• Stretch-compatible type: A type that more easily follows the movement of stretch outer fabrics.

How to Choose and Points to Note

Select based on the outer fabric thickness, direction of stretch, surface texture, and the desired final stiffness. If the interfacing is much stiffer than the outer fabric, the fused result may look unnatural, or the interfacing alone may pull when worn.

For thin or light-colored outer fabrics, attention is also needed to the color of the interfacing, adhesive bleed-through, and any texture showing through to the surface. The outer fabric and interfacing combination should be test-fused before mass production to check the hand feel and appearance.

• Check the stretch direction of both the outer fabric and the interfacing.
• Check not only after bonding but also after washing or cleaning.
• For collars and front plackets, consider the required stiffness separately for each area.

Bonding and Sewing Precautions

When bonding, it is basic practice to follow the specified temperature, pressure, and time for each interfacing. If the conditions are insufficient, peeling is more likely, and excessive heat or pressure may cause gloss on the outer fabric, shrinkage, or adhesive bleed-through.

After bonding, allow it to cool sufficiently before handling to stabilize the bond. During sewing, pay attention to steps between fused and unfused areas and to waving caused by differences in stretch, and adjust the needle, thread, and feeding conditions to match the outer fabric.

Knit interfacing is more flexible than woven interfacing and easier to match with stretch materials, but it is not an interfacing that stops all stretch. For areas that require strong shape retention or stretch control, use woven interfacing, nonwoven interfacing, stretch tape, or similar materials as appropriate for the application.

Frequently Asked Questions

How do you choose between knit interfacing and woven interfacing?

Knit interfacing is suitable for areas where you want to preserve the softness and stretch of the outer fabric. Woven interfacing has stability from its grain, and is used when stronger shape retention or stretch control is needed. The choice is made by test-fusing based on the outer fabric and the required stiffness.

Can knit interfacing be used for items other than cut-and-sew garments?

Yes. It is used not only for knit materials, but also for thin, soft woven fabrics and for shirts, blouses, dresses, and similar items that require moderate conformity. However, adhesive suitability varies depending on the structure and finish of the outer fabric, so prior confirmation is necessary.

What causes waviness after knit interfacing is fused?

The main causes are differences in shrinkage between the outer fabric and interfacing, mismatch in stretch direction, and improper temperature, pressure, or time during bonding. Fuse without stretching the outer fabric, test under recommended conditions, and then check the appearance after cooling and the condition after washing as well.