After sewing, press the seam flat while the pieces are still together to flatten the stitches into the fabric.
Before a curved seam is turned right side out, the seam allowance needs to be slashed to release tension or notched to remove excess fabric, depending on what kind of curve it is.
Clipping Inward (Concave) Curves
|When an inward curve is turned right side out, the edge of the fabric is shorter than the seam, causing it to bind up. |
Without clipping, it will look like this photo. Not so pretty, huh?
Fortunately, there is an easy fix for this.
|To solve this problem, you simply need to slash the seam allowance to allow it to open up and fall into a nice, smooth curve. The tighter the curve, the closer together the slashes need to be placed; every 1/2 inch is a good distance to start with. |
Use the tip of your scissors and snip into the seam allowance, being careful not to cut the seam. End the snips about 1/8 of an inch from the seam for best results. If your fabric ravels easily, make the cuts shorter to prevent the seam from tearing out. I typically cut shorter slashes to begin with and then adjust them based on how the curve looks when I turn it.
|When you are done snipping, press the seam open first and then flip the fabrics over. |
Pressing curved seams open is a little trickier than pressing flat seams. Use a tailor's ham, if you have one. If you don't have a ham (or seam roll), you can manage most seams on the ironing board by laying one of the fabrics flat on the ironing board (the blue fabric in the photo) and letting the other side (the yellow) lie loosely above the seam. Press slowly along the seam with just the tip of the iron (this helps keep you from pressing creases into the rest of the fabric). I have also made do in a pinch using the curved end of the ironing board.
Once you have finished pressing open the seam, turn the fabrics right side out and press the seam flat.
|This is how your inward curve should look when you are done:|
Clipping Outward (Convex) Curves
|When an outward curve is turned right side out, the edge of the fabric is longer than the seam, so the fabric bunches up along the seam. Without clipping, it will look like the one in this photo. The curved edge is uneven and there are bumps underneath the fabric so it won't lie flat. |
|To solve this problem, you need to remove the excess fabric by cutting notches into the seam allowance. Like the inward curve, the tighter the curve, the closer together the notches need to be placed; every 1/2 inch is a good distance to start with. |
Use the tip of your scissors and snip "V" shapes into the seam allowance, being careful not to cut through the seam line. End the notches about 1/8 of an inch from the seam for best results. If your fabric ravels easily, make the notches shorter to prevent the seam from tearing out.
|When you are done notching the seam allowance, press the seam open and the turn the fabrics right side out and press again. |
Your finished outward curve should look like the one in the photo when you are done. The edge is evenly and smoothly rounded and the seam lies flat.
|In most cases, clipping the seams as explained above works fine, but when dealing with very thin or bulky fabrics, there is an alternate way of clipping that can reduce the chances of the seam allowance showing through to the right side. Clip through only one layer at a time and offset the slashes or notches so that they no longer fall on top of each other (see photo for an example of offset notches). This gives the seam a smoother finish, especially when dealing with thick fabrics.|
A full circle is sewn in the same manner as an outward curve (if you think about it, a circle is two big outward curves put together). The seam allowance will be notched as explained above. The smaller the circle, the closer together the the notches will need to be cut.
I hope you enjoyed this installment of the Learning How to Sew series