Tuesday, July 1, 2014

Knit Fabrics

Happy Canada Day!

Last week we looked at woven fabrics, and this week we're going to do knit fabrics. The best way to really understand how knit fabrics are constructed are to learn how to knit. But that can take a lot longer than you might be wanting right now, so how about some paper crafts, instead?

Knit fabrics are stretchy. Think of any t-shirt you've worn, and you've got an example of knit fabric. This stretchiness can make knits more comfortable to wear, since they conform to your body more than wovens. But why are they stretchy? If you've ever unravelled a sweater or lost threads on a shirt, you might notice that the thread or yarn itself isn't as stretchy as the fabric itself.

Take some strips of paper, which are definitely not stretchy. Join together the ends of one strip with a piece of tape, so you have a loop. Then do the same with another strip, being sure to catch the first loop in the second before securing it. Do this a few times, so that you have a chain. While this isn't an accurate representation of actual knit fabric, since they aren't closed loops, it is close enough for a demonstration.

Now, take the ends of the chain in your  hands, and pull gently. You probably won't get much distance out of it, but you can see how the loops straighten out a bit and the chain stretches a little.

Like woven fabrics, knit fabrics have a lengthwise and crosswise grain, only they are made out of rows and columns of connected loops, rather than individual threads.

There are two basic types of stitches in knitting: knit, and purl. These two stitches are the foundation of just about every knitting pattern out there. Common knit patterns include garter, stockinette, reverse stockinette, ribbing, and lace. What you commonly think of as knitting is likely stockinette:

When working with knit fabrics, pay attention to how the fabric stretches, and how much. You can sometimes use knit fabrics with patterns which call for woven fabrics, but be careful: the stretchiness can change the way the garment sits once you finish it.

Commercial patterns that are designed for knit fabrics will generally specify what percentage of stretch is expected. To measure this, take a piece of your knit fabric, and measure 4" across the grain, and perpendicular to the selvage. Stretch it until it starts to resist, then measure again. If your 4" bit is now 6", you've gained 2", and since 2/4 = 50%, the fabric has a 50% crosswise stretch. Most pattern envelopes will have this sort of guide on the outside:

You can use this to stretch across the grain, and see if your fabric is right for your pattern.

Once you've chosen your fabric, you'll want to make sure you have some ballpoint needles for your machine. If you aren't sure why that matters, then come back next week for a discussion on machine needles!

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