Clipping, Notching, and Grading Seams
When sewing a pattern, you may have come across directions in the tutorial to “clip corners” or “clip notches into the seam allowance” etc. These are important steps for finishing some seam allowances before turning right side out, and cannot be skipped for best results. But clipping, notching, and grading seams are not the same thing, and each of these has its own specific uses.
Today, we are going to look at clipping, notching, and grading seams. What is the difference? How do you know when to do each? What will give the best result? And why do we need to do this? Today we will answer those questions!
In general, the easiest way to think about it, is that you need the seam allowance to fit within the sewn area- when the project is turned right side out, the seam allowance, which looks like it is to the outside after sewing, basically gets folded to the inside of the seam line when turned. So, we are always asking, “will the seam allowance fit into that space cleanly?” If not, we need to clip in some way. Different shapes of seams will need different types of clipping. Let’s take a look at some common ones!
Notching vs. Clipping Curves
Notching and clipping are two ways seam allowances are trimmed on a curve. To know whether or not a curve should be notched or trimmed, you need to look at the type of curve it is- concave or convex.
The simplest way to look at this, is to ask which has more space, the seam allowance or inside the seam? Look at these two pictures. One shows an outward curve and one shows an inward curve.
On these two images I drew lines on either side of the stitch line. On the dome-shaped curve, the seam allowance is MORE FABRIC than inside the seam. You can see the blue line is bigger than the purple line. Think of it like a rainbow. The top arc is going to be bigger than the arc nested under it. On the bowl-shaped curve, it is the opposite. The seam allowance is LESS FABRIC inside the seam. This is clear in the upside down rainbow- again I drew the blue line on the bigger curve, and the purple line is the smaller arc nested inside it.
So depending on the type of curve you sew, the seam allowance will contain more or less fabric than inside the seam. This is the key information you need for deciding whether to clip or notch…. to an extent! Notching is ideal for a dome shaped curve, clipping for a bowl shaped curve- IF the bowl shape curve is shallow like most necklines. In those case you can also notch. But you will need to clip if the curve is very small and deeply scooped. So what is the difference between clipping and notching?
Notching Curves
Look again at the picture of the convex (dome shaped) seam.
The seam allowance is bigger than inside the seam. So MORE fabric has to fit into LESS space. If you turn this right side out, you will have too much fabric trying to go into a tighter spot, which is going to cause bunching in the seam and you can’t get a smooth curve. You have too much in your seam allowance, so some of it has to be removed. This is why you notch the fabric. You are REMOVING fabric from the seam allowance, allowing it to fold neatly inside. Pinking shears makes this very easy. Look at the notched seam:
As you can see, half the fabric has been removed. Now instead of a bunch of bulk, each notch can neatly fold inside.
Clipping Curves
When the curve is concave (bowl shaped) the opposite is true. Now you have less fabric trying to fit into more space. Take a look again:
The seam allowance is smaller than the space it is going into. It needs to spread to fit. On stretch fabrics this typically is not an issue because the fabric can stretch into the space. But on woven fabrics, it will cause puckering as the seam allowance cannot stretch cleanly into the space.
So for this, rather than removing bulk, the answer is to allow the seam allowance to spread. To do this, you can clip vertical cuts into the seam allowance right up to the stitch line. This will let the fabric spread apart to fill the space.
With notches cut like this, the seam allowance can go into the seam space that is larger, spreading apart as needed.
Now, this type of curve is often seen in necklines. But in these cases, the curve is shallow enough that simply notching the same way you do with an outer curve works just fine, as it still allows plenty of fabric spread! But on a very small and very tight/deep curve, cutting straight vertical lines very close together can provide an even better result.
Clipping Corners
You will often come across directions to “clip the corners” after sewing a square angle. This is because there is way too much fabric in the seam allowance of a corner to fit nicely inside the seam. It will have far too much bulk. Take a look at this picture:
You can see that the outer seam allowance (blue) is significantly more fabric than the inner seam. There is no way for it to fold in neatly. So clipping the corner is an easy way to allow a crisp corner:
Cut like this, each side of the corner can press in independently, leaving a crisp corner.
Clipping a “V”
Clipping a v is like an extreme version of a concave curve. There is way less fabric in the seam allowance than can fit in the seam, plus you have the weird angle. You must clip this to allow the fabric somewhere to go!
On a v seam like shown in the picture, you would also need to clip the upper corner where it goes from a horizontal line down into the V:
Grading Seams
Last in our lineup of clipping, notching, and grading seams, let’s talk about grading! What does it mean to grade seams? If your seam is two pieces of fabric, you don’t really need to worry about bulk. But if you are sewing through many layers of fabric, the seam allowance can end up extremely bulky. You don’t want to cut all the seam allowance down evenly because it will just create a bulky ridge. The seam allowance should grade smoothly down for best results.
To grade the seam allowance, trim down the seam allowance and different intervals. In the pictures below, I sewed three pieces of fabric together. You can see that I cut one fabric way down, one part way down, and one I only trimmed a little. When the project is turned right side out, and I press the seam, it will have a gradual decrease and will be very smooth. Any time you are creating a bulky seam, consider if grading the seam allowance will help!
That’s It!
Clipping, notching, and grading seams is critical to excellent finished results in your project. Knowing which technique to use for each seam will help you get those perfect results each time! Clipping corners and Vs are pretty simple- just cut as close to the seam as possible without cutting through it. Clipping and notching curves can be somewhat trickier, but if you ever forget which to use just ask yourself “does the seam allowance have MORE or LESS fabric than inside the seam?” The answer will tell you whether your seam allowance needs bulk removed, or needs to be able to spread. Then, you will know what to do.
I hope this helps you get perfect seams each time!
