When you design a sweater in the yarn, color, pattern and fit you want using EPS, Elizabeth’s Percentage System, the last step before you cast on for the sweater is making a hat. She calls it your experimental swatch hat. Makes sense, since a hat is half the stitches of the sweater.
Knit it up in the pattern you invented with the gauge you got. Will everything work out as you planned? Whether it does or not, whether it shows you a few tweaks you’d like for your sweater or not, it’s a quick knit you can wear when finished.
A hat ensures your sweater isn’t a failure.
It’s especially important if you design a complicated sweater like an Aran sweater with multiple cable designs. You want it to turn out as great as the picture in your mind, plus fit just right, right?