Tuesday, October 14, 2014

Clipping and Notching and Grading, oh my!

Imagine this situation: you've sewn two pieces of fabric, right sides together, and you've turned your project right side out. Only, it looks weird and misshapen, and for some reason it bunches or doesn't sit right. I've done this many times, and usually it means I forgot to trim down the seam allowance.

Cutting your fabric after you've sewn it may seem like an odd idea, but reducing the bulk in key areas can make a world of difference in your final product, and all it takes is understanding a little basic geometry.

If you've sewn a simple rectangle, you've probably already clipped the corners of it. This reduces the amount of fabric that has to fit into the much smaller space when turned. The principle is similar for sewing curves: for convex seams, we have too much fabric in the seam allowance, while for concave seams, we have too little.

Convex Curves

For curves that go outwards from the main part of our sewing, we want to notch them by cutting little triangles out of the excess seam allowance.

Be sure to notch at regular intervals, or your curve may look wonky.

Now when you turn it, the seam allowance won't bunch up.

Anything that has rounded corners will be a convex seam, like the toe of a stocking, the hands and feet of simple stuffed animals, or scalloped edges.

Concave Curves

If your seam curves inward after turning, you actually have the opposite problem--you have too little fabric, and your seam can't stretch out.

Look at that, it won't even turn properly, pah.

For concave seams, you don't have to do a full notch; just do a single clip--enough to let the seam allowance stretch out.

Once you turn it, you can get a nice, even curve.

Examples of concave seams are collars and pockets (e.g., jean pockets). In many cases when you are doing concave seams, because the fabric can and does stretch, you may need to stay stitch the fabric to prevent overstretching... but that's a whole other blag post for another week.

Grading Seams
No, we aren't assessing your seams! I'm sure they look great. But in some circumstances, you may want to reduce the bulk of your straight seam allowance. This is especially useful if you're seeing with bulky fabrics, or in any case where the excess fabric creates a visible bump.

It's a little difficult to see from this fabric, but when you turn it, there is a little ridge. With most quilting cottons, this shouldn't be an issue.

To grade your seam before turning, separate the two sides of the excess fabric, and fold one side back, leaving one side free. This helps prevent accidentally cutting your main fabric while you trim one of the layers in half, like so:

Now when you fold it, the ridge isn't as visible.

Usually you would only grade a straight seam, but when sewing with bulky fabrics and doing curves, it's often worth applying the same justice to the excess fabric.

Keep in mind that all of these techniques are done with the expectation that your seams are going to be enclosed. You can't clip or notch a serged edge, either, since that would break the overlocking threads. But even so, knowing when and how to clip, notch, and grade is an extremely useful tool in your arsenal of sewing skills.

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