Intro to Interfacing - Part 1

Updated: Jul 25, 2021

Buying interfacing can be very confusing for beginners. It can be difficult to choose, buy and apply interfacing. So I have written this handy guide to interfacing which I hope some will find useful. First we look at what interfacing is, and how to choose types of interfacing; and finally, how to apply fusible interfacing. In next weeks' blog post, we will dive a little deeper and look at some of the specific numbers of interfacing from Vlieseline (as this is one of the most common brands supplying interfacing).

What is interfacing?

Interfacing is an additional layer applied to the inside of garments or other sewing projects, in certain areas only, to add firmness, shape, structure, and support to areas such as collars, cuffs, waistbands and button plackets; and to stabilise areas such as shoulder seams or necklines.

Interfacings come in two types: fusible or sew-in, three weaves: non-woven, woven and knit, and in different weights: light, medium and heavy weight. It is important to choose the correct type of interfacing for your garment and fabric. Pattern Companies will normally indicate if interfacing is required and what type you need.

When you buy interfacing, you need to decide:

  • Should you buy sew-in or fusible interfacing?

  • Do you need woven, non-woven or knit interfacing?

  • What weight of interfacing should you buy (light weight, medium weight, heavy weight)?

  • Which colour interfacing is most appropriate?

Sew-in or fusible interfacing

Fusible interfacing is by far the easiest to use, especially for beginners. It has an adhesive on one side which feels rougher. This side bonds with the fabric when applied with an iron, due to the combination of heat and steam. Fusible interfacing is suitable for most uses, but avoid it for:

  • very textured fabrics – the glue won’t bond well to the fabric

  • napped fabrics (e.g. velvet / fur) – the pressing needed to bond the adhesive will crush the fabric

  • fabrics that are very heat sensitive – e.g. sequins, metallics, vinyl fabrics (the heat can melt or distort the fabric)

  • fabrics with a very loose or open weave e.g. lace, mesh (the glue may seep through to the right side of the fabric)

For these types of fabrics, sew-in interfacing is more suitable. Sew-in interfacing is sewn on to the main fabric just like another normal layer of fabric, and is held in place by stitches. Sew-in interfacing can also result in a more natural shaping and drape as there is less stiffness to it.

Whether to use sew-in or fusible interfacing can make subtle changes to the drape of a garment. For most beginner sewing projects, you will be absolutely fine with fusible interfacing; in fact I don’t really recommend using sew-in interfacing until you are really comfortable handling multiple layers of fabric on the sewing machine. Badly sew-in interfacing can really affect the shaping of the garment and give it a poor finish, so unless you’re feeling super confident, and / or your sewing pattern or fabric demands otherwise, stick to the fusible interfacing.

Non-woven, woven or knit interfacing

Woven interfacing, like woven fabric, has a lengthwise and crosswise grain. When you cut woven interfacing, be sure to match the grain of the interfacing with the grain of the part of the garment to be interfaced, to make sure the two layers of fabric work together properly. Because of the need to match the grainline, it is less economical than non-woven interfacing, which can be cut in any direction.

Non-woven interfacing is made by bonding fibres together and therefore has no grain. You can cut it in any direction, plus it will not ravel, so it is particularly easy to use, and is suitable for most uses except stretch fabrics.

Knit interfacing is made by knitting the fibres together, and so it has an amount of stretch in it. Knit interfacing is especially suitable for use with jerseys and other stretch fabrics as it will stretch with the garment and not hinder it. If you apply woven interfacing to a knit fabric, you reduce the fabric’s stretch properties as the interfacing layer is unable to stretch with the outer fabric layer.

The decision as to whether to buy woven, non-woven or knit interfacing is usually dictated by the pattern and type of fabric you are using. As a general rule, non-woven interfacing is suitable for most tasks unless you are sewing with a jersey of stretch fabric in which case knit interfacing is appropriate. You only really need to consider woven interfacing for particularly fine fabrics such as sheers and silks, where a very natural shaping is essential to preserve the qualities of the fabric.

Weight of the interfacing