Using fusible interfacings for knit fabrics

- Sewing knits, Tutorials

Using fusible interfacings made for knit fabrics is a great way to add structure and stability to your knit garments. There are several knit fusibles to choose from and it is important to pick the right type for each project. So I thought I should do a guide on common knit interfacings and how I use them. I’m personally a big fan of using fusible interfacing for knits, especially since I like to add structured details to a lot of my garments, such as collars, buttonholes and pockets. And to put it bluntly, knit interfacings are pretty much a necessity in those instances for a satisfactory result.

Examples of when fusible knit interfacings can be used

  • Collars
  • Plackets
  • Cuffs
  • Pockets
  • Necklines
  • Sleeveless openings
  • Facings
  • Hems
  • Buttonholes and eyelets

 

Fusible iron-on stretch interfacing for knits 2 way stretch

2-way stretch fusible interfacing for knits

This is my favourite knit interfacing, and I always buy a lot when I can find it. It often has a chevron type of knit structure and stretches lengthwise, crosswise and diagonally. This one has never caused me any wrinkled or puckered situations. It is fairly light and gives the perfect amount of stability, especially great on medium to heavier knits.
Vliseline H609 is a version of this interfacing (Amazon affiliate link)

Use

  • Facings
  • Collars
  • Cuffs
  • Hems

Don’t use

  • Button plackets
  • Buttonholes and eyelets
  • Anything where you want to eliminate stretch

Facing stabilised with the 2-way stretch fusible

 

Fusible iron-on stretch interfacing for knits 1 way stretch

1-way stretch fusible interfacing for knits

This is similar to the 2-way fusible in hand and weight. But it only stretches crosswise (and diagonally) and has a slightly firmer hand too. I use this for button plackets, collars and cuffs on medium to heavier knits, where I want to eliminate stretch in only one direction. Also if you cut it on the bias you will also get a fair amount of stretch. Not as failproof as the 2-way chevron and sometimes I feel it doesn’t fuse as well, but that could be me getting a bad batch occasionally.

Use

  • Facings
  • Collars
  • Cuffs
  • Button plackets
  • Necklines
  • Shoulder seams
  • Buttonholes and eyelets (on knits that only has 1-way stretch, by placing the non-stretch direction of the fusible in the stretch direction of the fabric you will stop the fabric from stretching in any direction)
  • Pocket openings

Don’t use

  • On very lightweight knits as it will change the hand and make the fabric rigid. I also don’t like it on hems

 

Cuffs stabilised with the 1-way stretch fusible

 

Fusible iron-on stretch interfacing for knits featherweight 1 way stretch

1-way stretch light-weight interfacing for knits

This interfacing is very similar to regular featherweight fusible interfacing. It only stretches crosswise and is so thin that it doesn’t change the hand of the fabric much. Best for interfacing the second, underlying layer, of the fabric as this interfacing is the most likely to be distorted when stretched out a lot, especially on spandex knits. But smaller areas such as buttonholes are usually fine. You can also cut strips on the bias for just a smidgen of stability when needed.

Use

  • Facings
  • Collars
  • Cuffs
  • Button plackets

Don’t use

  • Eyelets
  • Avoid big areas on outer layers of fabrics, especially if the fabric is thin

Buttonhole stabilised with non-woven 1-way stretch. The non-stretch side is placed in the same direction as the buttonhole.

 Fusible iron-on stretch bias stay tape

Iron-on bias tape with reinforcement

If you need to stabilise necklines, sleeves openings and other rounded or diagonal edges, but also want to retain some stretch this is the best product among fusibles. The strips are cut on the bias but thanks to a chain stitch in the middle (which also works as a stitch guide) this tape is the perfect combination of stretch and stability.

Use for

  • Necklines
  • Sleeveless openings
  • Shoulder seams (if you want them to stretch a little)

Sports lycra knit neckline stabilised with bias iron-on tape

 

Brand names

Prym forming tape interfacing

Vlieseline bias stay tape  (Amazon affiliate link)

 

Some suggestions on pressing knit fusible

Use dry heat (unless stated otherwise) and always do a sample. When fusing on synthetic knit fabrics you might need to lower the temperature a bit, otherwise, the fabric might be ruined. Around 10 seconds is enough and let the fused piece set for at least 30 minutes. But I actually like to fuse and leave it until the next day as per an advice I was once given by a very knowledgeable person.

Final thoughts

Hope you found this guide was useful. Of course, there might be more knit fusibles out there, but these are the ones available in Sweden and I assume that it doesn’t differ too much from country to country. And if you are new to using fusibles with knit fabrics I highly recommend that you try it, as they can vastly improve the outcome, especially if you are sewing more structured knit garments.

 

How to use fusible iron-in stretch interfacing for knit fabrics A sewing tutorial

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4 Comments

  • Reply
    COREY
    April 13, 2018 at 1:34 am

    Johanna, I have a few questions for a topic not covered in your book. I am guy, no surprise there and I would like to make up some underwear for myself. The underwear I currently purchase is made by jockey, and its a sports boxer brief, making up a pattern based on a pair if fine, i can do that. What I want to know is what fabric should I use, for comfort, stretch that comes back, easy to wash for example, when i travel i often have to wash my things in the sink/tub in the hotel room, and what kind of elastic do i need for a waistband that won’t roll and is comfortable, that won’t bit into my sides. Further, the fabric has to have moisture wicking properties since sweating and chaffing are very uncomfortable. Thank-you in advance.

    • Reply
      Johanna
      April 15, 2018 at 1:36 pm

      Hi Corey! My favourite underwear material for the kind of purpose you describe are microfiber knits. It is very soft, almost like cotton but is usually a poly/spandex mix, quick drying and easy to wash. It can be kinda tricky to find sometimes, I have bought mine from underwear notions companies, so that should be the first stop, but I’m sure there are more stores internationally. A quick google search shows me that Jockey uses that fabric too for their undies. I love that material!

  • Reply
    Adrianne
    April 13, 2018 at 2:20 pm

    Thanks for all the info! I will definitely save this for future reference! For Corey: You should check out Thread Theory. You said you have your own pattern, but they also list sources for materials https://threadtheoryblog.wordpress.com/2014/05/02/looking-for-elastic-for-your-comox-trunks/. Good luck!

    • Reply
      Johanna
      April 15, 2018 at 1:37 pm

      Awesome! The Thread Theory is truly doing a great job in an underserved market

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