Fusible Interfacing

Interfacing is a layer of fabric added to selected parts of a garment to give them body, crispness or stability. It's what keeps a collar standing, a cuff flat, a waistband from rolling, a button band from stretching, and a buttonhole from distorting. Fusible interfacing has heat-activated adhesive dots on one side. Pressed onto the wrong side of the fabric with an iron, it bonds permanently, so there's no basting. Sew-in interfacing has no adhesive and is basted or caught in the seams instead.

Where interfacing goes

Pattern pieces usually tell you, but typically:

• Collars (upper collar, or both layers), collar stands and cuffs.
• Facings at necklines, armholes and front openings.
• Button and buttonhole bands and plackets.
• Waistbands.
• Pocket welts and flaps, and pocket openings.
• Hems on jackets and coats.
• Strips along zip openings and shoulder seams, to stop them stretching.

The three types

• Woven fusible has a grain like fabric. It behaves most like the fashion fabric, so it gives a natural result. Cut it on the same grain as the piece it supports.
• Knit (tricot) fusible stretches in one direction. It's soft and drapes well. It's good on knits, and on lightweight wovens where a woven interfacing would feel stiff. Weft-insertion interfacings, a knit with extra yarns laid in, are a firmer version used in tailoring.
• Non-woven fusible is made of bonded fibres with no grain, so it can be cut in any direction. It's inexpensive and fine for crafts and stiff details, but on garments it can feel papery, crease permanently, and separate from the fabric after many washes.

Weights run from featherweight to heavy. Match the interfacing to the fabric, then go a little lighter if in doubt. Fusing makes the interfacing feel firmer than it does on the bolt, and too heavy an interfacing makes a collar board-stiff and visible from the outside.

Testing first

Fuse a scrap of interfacing to a scrap of your fabric before anything else. Check for:

• Stiffness: fold and drape it. Does it behave the way you want the collar or waistband to?
• Bubbling or puckering after it cools.
• Show-through: adhesive dots can show through as a texture on smooth, light or shiny fabrics such as satin and fine silk.
• Colour: white interfacing can make dark fabric look lighter at the edges. Charcoal or black interfacing is available for dark fabrics.

Fusing it properly

1. Pre-shrink the interfacing if it's likely to shrink. Many woven and knit fusibles shrink slightly when steamed. Soak them in warm water for 10-15 minutes and let them dry flat, or hover a steam iron above them, without touching, before use. Check the manufacturer's instructions.
2. Cut it slightly smaller than the piece, trimming it out of the seam allowances on medium and heavy weights to reduce bulk. Many sewists trim about 1/8" (3 mm) inside the seamline.
3. Place it adhesive side down on the wrong side of the fabric. The adhesive side feels slightly rough or shows small shiny dots. Fusing it the wrong way up glues it to your iron.
4. Cover with a press cloth. This protects the iron and the fabric. A damp press cloth adds the steam many fusibles need.
5. Press, don't slide. Hold the iron down firmly in one spot for about 10-15 seconds (or as directed), lift it, and move to the next section, overlapping slightly. Sliding shifts and wrinkles the interfacing.
6. Turn it over and press again from the right side.
7. Let it cool completely before moving the piece. The adhesive sets as it cools, so moving it while warm can cause bubbles.

Sew-in interfacing

Sew-in interfacing is better for:

• Fabrics that can't take heat or steam: some silks, velvets, sequinned and metallic fabrics, vinyl.
• Napped or textured fabrics that fusing would flatten.
• Very fine or sheer fabrics, where fused adhesive would show. Silk organza is the classic sew-in interfacing for these.
• Traditional tailoring, where hair canvas is shaped with pad stitching and steam.

Baste it to the wrong side within the seam allowance, then trim it close to the stitching after sewing the seam.

Troubleshooting

Bubbles or wrinkles after washing: the interfacing wasn't pre-shrunk, wasn't fused long enough, or is a non-woven that has separated. Choose a better-quality woven or knit fusible, pre-shrink it, and fuse it fully.

Collar too stiff: the interfacing is too heavy. Use a lighter weight, or interface only the upper collar.

Edges show as a line on the right side: heavy interfacing ends abruptly. Trim it out of the seam allowances, or use a lighter weight.