We get a lot of questions about interfacing here at Core Fabrics! The unsung hero of garment construction, interfacing is crucial to getting beautiful sewing results in many sewing projects. Let's unpack just exactly what it is, how to use it, and why it's such an important material to have in your sewing stash.

What is Interfacing?

Interfacing adds structure and stability to fabric. Think of it like the "studs" in clothing construction - it helps support the garment at key architectural areas. It also helps provide crisp edges and corners, and prevents areas like necklines from sagging. You'll most often see it used in collars, plackets, cuffs, and facings.

For most projects, only small key areas are stabilized with interfacing, but for some garments like jackets, you may be asked to interface large pattern pieces (like the entire coat front), or in the case of some handbags, all pattern pieces. Interfacing is especially important when sewing loose weave fabrics and for tailoring fabrics like wool coating and suiting. Interfacing will help prevent these fabrics from stretching out in high stress areas like armscyes and hems.

There are many types of interfacing, with different features such as weight, colour, structure, and fusibility. Some interfacings must be sewn in, while a majority of modern interfacings are fusible, meaning that they come with a layer of glue dots on one side, which are then melted with an iron to join the interfacing seamlessly to your main fabric.

Fusible vs. Non-fusible

In the past, non-fusible interfacing was much more common, but these days fusible interfacings are the default option in sewing patterns and ready to wear since they "merge" with the fabric when correctly applied. They are affordable and easy to use, and mostly what we carry here at Core Fabrics. If you've had poor experiences in the past, know that fusible interfacing has come a LONG way in the last decade or so. We only stock super high quality, industry level fusibles in our shop, and everything we have carry has been throughly road-tested by us in-house.

That said, non-fusible interfacings have their place, although they are mostly used in classic tailoring and couture applications these days. You can use any stable woven fabric as sew-in interfacing, from cotton muslin to poplin, canvas and flannel; it is applied by basting in place before sewing the final seams. Silk organza is also a lovely sew-in interfacing as it adds structure and stability while remaining light, breathable, and drape-able (it is very commonly used in couture sewing for just this reason). We also love horsehair canvas, to add supple but stable structure to coats and jackets in key areas like the breast and shoulder.

Understanding Interfacing Weights

When looking for the right interfacing for your project, try to match the weight of your interfacing to the weight of your fabric. For example, if you are sewing a fine, floaty dress, you want a soft, lightweight interfacing that flows with the lines of the garment.  Likewise, if you're sewing a heavy weight garment, you want a firmer interfacing that can stand up to the structure of your fabric.

• Lightweight interfacing is perfect for drapey projects, such as viscose, silk, and lightweight cottons like voile and batiste.  
• Midweight interfacing works well for the waistbands of jeans, tailoring applications, and midweight fabrics.
• Heavyweight interfacings significantly stiffen the fabric they are bonded to, and are typically used for hat brims, bags, and anything that really needs to hold its shape and structure.

Interfacing Weaves

There are many types of interfacing on the market, and sewists often get confused when faced with the options of knit, woven, and non-woven interfacing. Each type has it's time and place as you'll see below.

• Non-woven interfacing is made up of fibres bonded together without weaving or knitting, meaning that it is typically quite stable and does not shrink much when washed. This can sometimes have a paper-like feel since it's made into sheets from a pulp like product— make sure your non-woven interfacing isn't too stiff for your project.
• Woven interfacing mimics the weave and drape of fabric, offering the stability and structure of a second layer of woven fabric in your project.
• Knit interfacing is built to stretch, and is ideal for fabrics that need to retain stretch and movement, while still requiring some stability and structure. Use knit interfacing for knits, obviously, but also for stretch wovens, and areas like jean waistbands where you want a touch of give for comfort.

• Weft interfacing is created with threads woven through knit stitches, so it is stable along both grains, but soft enough to allow the main fabric to drape. It is ideal for tailoring applications like coats and jackets.

How to Apply Fusible Interfacing

It is very important to apply fusible interfacing the right way. You need to use sufficient heat and steam to melt the glue so it can merge with the fabric it's being fused to. If your interfacing isn't properly applied, you may experience bubbling later on in your final project.

Some types of fabrics can be difficult to fuse, especially if they have an uneven texture. When in doubt, test and wash scraps to see how your particular fabric responds to the fusible you are using. When provided, follow the manufacturers directions to correctly apply the fusible you are using.

The following tips should give you good results when fusing interfacing to your fabric:

• Pre-wash, pre-shrink, and press your fabric— never apply fusible interfacing to wrinkled fabric.
• Some interfacings may need to be pre-washed and pre-shrunk (the interfacings we carry are generally pre-shrunk and do not require this step). If you are unsure, it's better to be safe than sorry! Gently hand wash your interfacing in lukewarm water and hang to dry.
• Use a press cloth like silk organza or lightweight cotton to protect your iron and fabric.
• Set your iron to medium to high heat (cottons can take higher heat, while more delicate fabrics like viscose are better on medium). Low heat may not be hot enough to melt the glue.
• Place your fabric pieces with the wrong side up, and lay your interfacing glue-side down against your main fabric. Use a pressing cloth to protect your iron from picking up any glue from the edges of your interfacing, and press down for 10-20 seconds. You can also hit it with a bit of steam.
• Lift and move your iron to the next spot - sliding your iron can distort and stretch the fabric.
• Let the fabric cool before moving it from your ironing board, to ensure the glue is set and your interfacing is secure.

Cutting Fusible Interfacing

For stable fabrics, you can simply cut the interfacing using your pattern piece. For lightweight fabrics, there is no need to trim the interfacing from seams. However, if your interfacing is on the heavier side and you are concerned about bulk in your seams, you can cut the interfacing slightly smaller - just ensure your stitching will catch the interfacing or else you are losing the stability advantage!

If you need to interface a lot of smaller pieces or are working with a shifty fabric, you may want to try block interfacing. This requires interfacing a larger piece of fabric that you can then cut your pieces from.

Sustainability

Most interfacings are made out of polyester, and while this is not a sustainable material, our selection of recycled interfacings at Core Fabrics allows us to keep virgin polyester out of the supply chain. We are continuing to search for more sustainable options as we grow. 

Phew! We hope that answers any and all of your interfacing questions - let us know in the comments if you have any tips to share or further questions for us!