Which yarn to use

I’m in the beginning stages of making my first sweater. (Don’t tell my sister, I learned how to knit with the idea of Weasley sweaters. YEARS later, no sweater. The scarves were a hit though.)

I’m in the look at all the patterns and think about yarn part.
As for yarn, I’m thinking about how wonderful and soft the things I’ve made out if cotton are. But then, I’m thinking that cotton shrinks.
So I wonder: is cotton yarn pre-shrunk?
And if it’s not, then what? Can I wash it and get it to shrink as it might before I knit, or do I do the gauge swatch to end all gauge swatches and use it to figure out how much change in size there will be with washing? (Oh the math hurts my head just thinking about it.)

Cotton can be wonderfully soft but it can stretch out of shape, especially in sweaters. I haven’t had a problem with it shrinking so much as with it pulling out of shape and sagging (ugh). A cotton/wool blend may work better and give a little more stretch and bounce back to the fabric.
Either way, washing the knit swatch is a good idea. Take the measurement on the washed swatch and see if you can get gauge be adjusting the needle size before you worry about the math.
Good luck with it!

Agree with salmonmac. Cotton’s big problem with sweaters is the lack of elasticity. If you want a fitted sweater, you don’t want to go with all cotton as it won’t be fitted by the end of the day. Something with less shape that already starts out baggy might be OK.

Three ways to deal with cotton’s stretch factor - get a blend with wool or acrylic, knit at a tight gauge and use lighter-weight yarns. (Cotton is really heavy.) Blends with rayon or silk will provide better drape as well.

If you really want 100% cotton, look for mercerized cotton. It’s more shrink-resistant and sturdy. Not to mention, a little silky feeling. Oh, and less likely to shed.

As to the gauge swatch, are you assuming the end product will be tossed in the dryer? Shrinking isn’t likely to be an issue if you’re laying it flat to dry as you would with most delicate knits. If you start with a machine-washable cotton that also says to tumble-dry, you’ll probably be OK. Many still say to lay flat to dry or tumble-dry a little, then lay flat to dry, even if they’re machine washable.

I’d work up a single swatch using three needle sizes, probably two apart, so 4, 6 and 8. Measure before you wash and dry, measure after you wash and dry. Then figure out any gauge change by percentage and use that to decide on your final needle/gauge choice rather than keep making swatches. Assuming they all shrink the same. :slight_smile: You might find you get less shrinkage naturally at a tighter gauge.

[I have got to start writing shorter answers! Sorry for the encyclopedia!]