Interfacing is a layer applied to the wrong side of fabric. It stays in the garment. It varies along three axes: how it attaches (fusible or sew-in), how it is made (woven, knit, or non-woven), and how heavy it is. Once those questions are separate, choosing is straightforward. One rule resolves most doubt: interfacing should never be heavier than the fabric it supports.
What interfacing does, and where
Interfacing adds body, prevents stretching at points that take strain, reinforces areas that will be cut or fastened, and holds a shape the fabric could not hold alone. Most patterns specify where to put it.
Collars and collar stands
An uninterfaced collar has no roll line and wilts within an hour of wear.
Cuffs and plackets
Both sides of a button placket, so the buttonholes and the buttons have something to hold onto.
Waistbands
Without interfacing, a waistband concertinas the first time you sit down.
Facings
Interfacing stops the facing edge from stretching and stops it showing through as a soft ridge.
Buttonholes
In every fabric. A buttonhole in uninterfaced fabric distorts into an oval within a few wearings.
Pocket openings and welts
Anywhere you cut a slit that must hold its shape.
Zip openings, especially in knits
A narrow strip of knit fusible along the zip line keeps the opening from waving.
Bag panels and bases
Heavy and craft weights, for structure rather than support.
Hem allowances on soft fabric
A light strip in a fine or drapey hem gives it enough weight to hang straight. Listings sometimes name rayon or crepe for that hang. Rayon is a manufactured fiber. We recommend a light knit tricot on lawn or washed linen when you want that hang from a natural fiber.
Shop interfacing by weight and type, or browse sewing notions.
Fusible or sew-in
Fusible interfacing has heat-activated adhesive dots on one side. You press it on and it bonds. Sew-in has no adhesive and is basted into the seam allowance.
We recommend fusible when the fabric can take a hot iron and steam: most cottons, linens, wools, and stable knits.
We recommend sew-in when heat would ruin the fabric: vinyl, faux leather, sequins, metallics, some synthetics, and anything with a pile you would crush, such as velvet or corduroy. Sew-in also leaves the two layers free to move, which is softer.
Fusible web is adhesive with no substrate. It is not interfacing. It belongs in appliqué and hems. Fabric glue covers web, glue, and hem tape.
Woven, knit, or non-woven
Match the interfacing construction to the fabric construction. Woven on wovens. Knit on knits.
Woven: has a grain. Cut it on the same grain as the fabric, except on a shirt collar, where bias gives a nicer roll. We recommend it for shirt collars and cuffs, plackets, waistbands, and tailored facings.
Knit (tricot or weft insertion): stretches crosswise. We recommend it for jersey, soft tailoring, drapey wovens, and a zip opening in a knit. When you are unsure, we recommend knit tricot fusible.
Non-woven: no grain, papery and crisp. We recommend it for bags, craft projects, pocket welts, and buttonhole reinforcement. Garments you want to drape work best with woven or knit.
Choosing a weight
The same weight as the fabric, or lighter. Never heavier. When you are between two weights, take the lighter.
| Weight | Fabric | Use |
|---|---|---|
| Sheer or featherweight | Chiffon, georgette, voile, silk, fine lawn | Facings and small details. |
| Lightweight | Lawn, shirting, poplin, light linen | Soft shirt collars, blouse facings, sleeve plackets. |
| Medium | Quilting cotton, chambray, mid-weight linen, twill | Collars, cuffs, plackets, waistbands, most facings. |
| Heavyweight | Canvas, denim, duck | Bag panels and bases, structured belts, hat brims. |
| Craft or extra firm | Structure, not support | Fabric boxes, structured bag sides, brims. |
| Fusible fleece | Padded makes | Laptop sleeves, quilted bags, padded straps. |
| Foam stabilizer | Bag-weight wovens | Bags that stand up without feeling like board. Usually 2 to 3 mm and sew-in. |
| Hair canvas | Wool suiting | Traditional tailoring. Sew-in. |
The fabric we stock is 100 percent natural fiber. The rare exception is recycled spandex under 6 percent, used when a woven needs stretch. Recycled polyester is a named synthetic. It is not a natural fiber.
How to fuse it
- Test on a scrap first.
- Preshrink woven interfacing.
- Adhesive side against the wrong side of the fabric.
- Iron on wool or medium, about 148 C or 300 F.
- Always use a piece of fabric between the iron and the work.
- Press, do not iron: straight down, 10 to 15 seconds, then lift.
- Let it cool completely flat.
- Trim interfacing out of seam allowances at collar points and corners.
When it goes wrong
Bubbling after a wash
Interfacing shrank or the bond never set. Preshrink, full dwell time, cool flat.
Adhesive speckling
Too much heat or interfacing too heavy. Lower the iron and drop a weight.
Visible ridge
Pink or grade the edge, or interface the whole piece.
Cardboard collar
One weight lighter next time.
Cracking on a knit
Use knit tricot or weft-insertion, always, on knits.