Thursday, September 15, 2011

My First Lace and Steam Science (Yes, They Go Together)

So remember back in the day when I was planning to knit some lace? I started the project not long after I blogged about it, at the beginning of May. It's the Heartland Lace shawl pattern, downloadable here for free. If you have a Ravelry account, you can see it here.

To be fair, it didn't actually take me four months to make this. I finished it about a month and a half ago, and then it sat in a ball in the corner till I got around to blocking it last night. It didn't take all that long, but weighing down the corners of the towel was a little obnoxious - I ended up with three stacks of books, a CD case, and a picnic basket holding it taut.

For those who don't know, "blocking" means stretching the finished piece into the desired shape, and then steaming it with an iron. This means pinning it into place, usually on the ironing board or on a towel. I actually didn't have enough pins to block this whole thing at once, so I did it in halves, with pins down the middle so that it didn't stretch oddly.

I love the way it turned out. I did lots of measuring to make sure I was stretching it accurately on both sides, and I think it's not bad for a first lace project. In the end, it's even difficult to see the mistakes... unless you know what you're looking for, and are looking closely.

Friend Kaelin, as I was explaining how steaming keeps it in place, asked if it wasn't weird that it does that. So then I started wondering about the science of heat and steam in regards to fabric. Because I'm a geek, and that's what geeks do.

According to various sites, heat causes the tiny strands of taut fiber within fabrics to loosen - on a molecular level. When the fabric cools, fibers retain their new, stretched shape. Steam allows the heat to go deeper in the fabric, affecting more fibers. This is why spraying an item with water before ironing (or using steam) is more effective than just using a hot iron.

But it's even more sciencey than just that. Many fiber molecules have hydrogen bonds, and so does water. The two hydrogen bonds kind of mesh together, stretching the fiber molecules into a different shape, which is held after the water evaporates. Certain fabrics, like cotton and wool, require the addition of water to help loosen the fibers on a molecular level.

And I thought I was just making something pretty.

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