Patterns tell you to clip a lot.
They don't really tell you why, how much, or how often.
Those are the important parts.
To make it plain as it can get I would say the thing to remember is you have to clip a seam allowance most of the time when it needs to be attached to some other shape that is different (say a curved neckline to a straight collar for example) or otherwise stretched in some way to liberate the fabric to go around a corner, in a insert as one case.
You don't clip seam allowances that are turned inside, when constructing a round pocket or a curved shaped collar as some examples. For that you need to notch, which is another thing all together, that I will talk about in the next post.
For now back to clipping.
This is what you need to know:
- To get the stretch advantage of clipping you can't clip like a mouse. This is no time for nibbling at the seam allowance, a victim of the fear that you are not creating a Sturdy Garment. Clip right to almost the seam allowance and be a brave girl about it.
- As security however put a line of stay stitching (straight stitches, usually a shorter stitch length) in just within the real stitching line. This will act as sort of a dyke to keep the clips for eroding into the garment. You can also, in an instance when you are doing a single clip as in clip to the large dot, iron a small piece of fusible knit interfacing under the area to be clipped, to achieve the same thing but without having to worry about having stay stitches showing later that you have to pick out.
- Clip a lot, don't be afraid to fringe it almost. This is not a here and there job. The rule is to clip as often as necessary for the fabric to be able to be pulled into a straight line - this will vary by the tightness of the fabric weave btw. A gabardine, as shown below, might need to be clipped every 1/4" or so, a loosely woven linen every 1/2". Keeping clipping and pulling the seam straight to see how you go.
Here is an example which hopefully makes this all clearer.
A while ago I made a wool gabardine coat. The neckline was obviously round and the collar more or less a straight piece.
Common situation and you are there every time you yourself put a collar in a blouse.
You would also know that there is a tendency when the collar gets sewn into the neckline for there to be little pleaty things that annoyingly appear along the stitching line along the neck edge.
You are producing these little pleats you know by the simple task of trying to sew a straight thing to a round thing.
The solution is to turn that round edge into something straight so the two edges are the same in nature and will sew together naturally.
You get that curved edge to transform into a straight one by clipping. Here is what it looked like once had clipped the neckedge on that coat:
A lot more clips than you expected right?
True but look at how straight that seam line is, how large the spaces between the clips are - indicating to me how much this seam allowance had to be freed before it could be straight - in my mind representing in each of those spaces potential little pleats of fabric that could have been caught in the stitching line.
Pretty neat trick, eh?