Intro to Hat Geometry
I am afraid that in an earlier post that I made an error in geometry. This would marr the honor of my high school math teacher, Mr. Zimmerman. He was not a man who taught me badly. The error is mine. It is also probably related to the number of years since I sat in Mr. Zimmerman's classes, with the boys, and learned these concepts. No, I'm not saying how many years.
I am often startled at how much math and geometry is used in beautiful and well-crafted knitting. Is it any wonder that it is taught to small children to assist them in learning and practicing these concepts?
Diameter of a hat is the length of a straight line going from one side of the hat to the other. Circumference is a curved or circular line, going around the edge of the hat on the outside. The circumference of a hat should be much larger than the diameter. (The radius is half of the diameter, just in case that word is rattling around your head also.) And, just to remind you, the human head is rarely circular, in the geometrical sense. It is closer to oval, and almost always unique. The diameter ear-to-ear will be different than the diameter forehead-to-nape. Obviously, not a circle.
And just to throw in more confusion, there is hat size, which is completely different. Lifted from this article from our friends at Wikipedia: " A numerical hat size is merely the average diamaeter of the head, determined by measuring the circumference of a person's head about 1/2 inch (1.3 cm) above the ears, dividing by pi (3.1416), and rounding to the nearest centimeter or eighth inch."
For an adult woman's hat, the circumference of the hat should be, roughly, 20-21 inches. For me, just in case you are gift-giving, it should be 22. Yes, I said it. I have a big head. Most off-the-shelf hats, and one-size-fits-all hats do not fit me.
For hand-knitted hats, the circumference of the hat should be slightly smaller than the circumference of the wearer's head. (Berets and other deliberately oversized hats can, of course, be different.) This is because of two main things. 1) Knitted fabric is usually quite stretchy. 2) Knitted hats rely on a little bit of stretch to fit well and to stay on the head. This is one reason for the ubiquitous ribbed watch cap hat. Ribbed fabric is easy for most knitters to produce, and is very stretchy and, thus, makes an excellent hat.
Crochet, being inherently less stretchy than knitting, has its own challenges in creating hats. I think a crocheted hat must be closer to the actual head measurement than does a knit hat.
I found this nice reference about sizing kids hats at the website for Little Lids. (They've got great kids hats!!) Note how quickly a child's head becomes an adult or near adult sized head. This makes for easy gift giving. I also use the size listing for preemature babies at Bev's Country Cottage.
Thankfully, knitted hats are much easier than hats created using felt or buckram or any other method.
That being said, my current house-elf hat, is knit flat, according to Sally Melville's pattern, from p. 54 of The Knit Stitch book. The fabric has a measured length of 18 inches, which means, when I sew it up, the finished hat is likely to have a finished circumference of slightly less than 18 inches. It should fit an older child or small-headed adult. Again, I dislike the yarn, so it may end up as a charity drive gift.
The yarn is not bad, it's a fine german sock yarn (Lana Grossa). It would make a fine sock. But, silly me, I chose to knit it as a hat. It's not the yarn's fault that I didn't listen to it.