When and How to Block Fuse Interfacing

This content was originally written for Indiesew and has been adapted for this blog. It was originally published on February 10, 2019.

Today I wanted to bring you a tutorial on block fusing interfacing. Over the past few years, I have found this technique to be incredibly useful in shirt-making, or anytime I need to interface pattern pieces.

It's very straightforward; a total beginner can do this. In fact, I would argue that newbie sewists should block fuse their interfacing to make fabric cutting a bit easier.

What is block-fusing you ask? Simply put, block fusing is the process of cutting a large block of fabric and interfacing the same size. They're fused together and the corresponding pattern pieces (that require interfacing) are then cut from the block. You'll find out why it's important below.

When To Block Fuse Interfacing

This method can be used for most sewing projects, but here's a guideline of when it's most appropriate:

1. When you're working with lightweight, shifty fabrics. It can be hard to interface pattern pieces when you're working with lightweight fabrics like challis, crepe, and voile. The pattern pieces can shape-shift before you get the interfacing fused to them, making it hard to iron the interfacing onto the pattern pieces perfectly.
2. When you've got plenty of fabric and interfacing to work with. Block fusing often creates a bit of fabric and interfacing waste, unless you work in really small blocks. Don't use this method until you've looked at the fabric layout charts in your pattern and you know how the pattern pieces are supposed to be arranged.
3. When your interfacing pieces are the same size as your pattern pieces. Before starting this process, check to make sure your interfacing pieces are the same size as the corresponding pattern piece. Some interfacing pieces may be smaller to reduce bulk in the seam allowance. For those scenarios, block fusing will not work.
4. When you have many pattern pieces to interface. Block fusing is especially useful when you have several pattern pieces to interface, like when sewing a button-up shirt. This method will save you time, because you only have to do the fusing step once.

For this tutorial I'm using a rayon challis fabric from my stash in a tropical print to sew a pair of pajamas. I'll be block fusing the front facing and top collar pieces. I'm using a lightweight, tricot interfacing.

How to Block Fuse Interfacing

Does block fusing sound like it'll work for your project? Great, here's how you do it:

First, lay your pattern pieces to be interfaced out on one end of your fabric to determine how big of a rectangle, or block, you'll need. For lightweight fabrics, I rip the fabric (both on the grain and cross-grain) to get the size block I need. You can also cut your fabric with scissors if you don't feel comfortable ripping or you need an odd-sized block.

Side note: I actually work in "blocks" for cutting all of my pattern pieces (not just for fusing interfacing). I'll rip one block for my bodices, another for my sleeves, etc. I find it's much easier to cut from smaller blocks, rather than having a bunch of fabric hanging off the edge of the table. Also, by ripping the fabric to form the blocks, the block is perfectly square, making it easier to arrange the pattern pieces on the grain. But beware, only use this method if you have plenty of fabric to work with.

Next, cut a piece of interfacing the same size as your fabric block.

Then, fuse the interfacing to your fabric. Be sure to use lots of steam to fuse the interfacing properly.

This is what your fused block should look like:

Finally, cut your pattern pieces out like you normally would.

This is what your fused pieces should look like, far neater than when the fabric and interfacing are cut separately.

If you haven't yet, give block fusing a try on your next sewing project! I think you'll find that this method saves you a lot of time and results in a super clean finish.

Happy sewing!