That's right. PLEATS. Like what you put on a skirt.
And, why yes, I AM about to start working on a skirt. Thank you for asking.
I am, as usual, getting way ahead of myself. You see, I've been feverishly working on sewing a reproduction 1860's dress. Specifically, it's a sheer dress with bishop sleeves. See, some time back I decided to get serious about the idea of getting together a period costume (the period being the mid 1800's). I purchased a lovely, well-made dress online (a black-and-white-and-dark-green-plaid dress with pagoda sleeves and a white collar). While I like the dress, I was somewhat frustrated by the fit, because I have an unusual, petite shape. Clothes very rarely fit me well. In any case, I thought to myself, how hard could it be?
Cue my maniacal laughter after weeks of figuring this all out from scratch. See, I have no real sewing experience. Luckily, I'm pretty good with spatial things and am both artistic and a good draftswoman. So I was able to art my way out of problems or engineer my way out, for lack of a better way of putting it. For instance, I free-handed a few lines for the pattern to alter them, and I had to figure out button placements using math.
In any case, there are a few more blog posts about the sewing of the bodice, but the bodice is now complete (hurrah!).
The next step is the skirt. And this requires pleating. Lots and lots of pleating.
See, I have to get 160" of fabric down to a 26" waist (there will be another 1" on either side of this that will be un-pleated; these two inches will overlap and result in one more inch, for a total waist of 27").
And that--getting that much fabric down to so little--requires many pleats. And I have been trying and trying to figure out the math. Yes, I was sitting here doing algebra. Or at least, I was trying. And I was becoming increasingly frustrated. I was trying to work out a formula to convert the overall inches to the waist inches and to simultaneously tell me how big to make my pleats and how much to overlap them, and . . .
Well. It's enough to boggle the mind. I set down my calculations and, in frustration, took a break. A bathroom break. As I walked to the bathroom, I thought to myself that there must be a much simpler, more practical way to figure this out. Screw math.
And then it hit me. Divide the total amount of fabric (160") by a certain number of pleats. Actually, let's make it simpler. I have to pleat the skirt in four sections. So let's take 40" and divide it by, say, 20 pleats. So I would mark every 2" on my fabric. Each of those will be one pleat. Now, I take my 6.75" (which is 26"/4, because, again, this is a one-quarter section of the total waist length of 26") and I divide that by 20, as well. That's 0.3375" (close to 3/8"). I now have 1/20 of the total fabric and 1/20 of the waist length. All I have to do is reduce each 1/20 of the total to 1/20 of the waist length. In other words, I reduce every 2" section I marked off to 3/8". By the time I've made 20 pleats, I'll have used 20 twentieths of the total fabric (i.e., 100% of it) and created 20 twentieths of the waistband (i.e. 100% of it).
How do I reduce each 2" to 3/8"? First, I mark out 3/8" on a card, for ease. I put one edge of my 2" section on the first 3/8" mark, then pinch together that 2" section until its second mark meets the second 3/8" mark. That fabric I just pinched up is my pleat. Making sure both my 2" marks are still touching both my 3/8" marks, I lay flat the fabric I just pinched up. It should make a neat fold. I have now made one pleat that uses 2" of fabric that advances me along the waistband by 3/8". If I do this 20 times, I will have used 40" of fabric and made a waistband of (about) 6.75". That's just right for my purposes. I repeat that four times, for each section of my skirt, and I'll have used all 160" and made a waistband of 26".
I'm sure this will all make much more sense with pictures...
But, to summarize: decide on a number of pleats (this is arbitrary, but a nice round number is easiest). Divide the total length of your cloth by that number, and mark this interval out on your cloth. Also divide the desired length of your waistband by that the desired number of pleats. Then pinch together the marks you made on the fabric until what's left is that second number (waistband/number of pleats). The excess you pinched up is your pleat.
This is actually a fairly simple technique, with very little math required.
I will try to spruce this up with pictures soon.