Thickness. Socks made from fingering weight yarns like Sock-Ease or LB 1878 are thin enough to be comfortably worn inside of shoes. Yarns thicker than sport weight are ideal for making house socks or boot socks.
Durability. Socks usually get a lot of wear and tear, so stronger fibers like wool will help them last longer. Yarns that are blended with nylon add even more strength.
Washability. While you don't have to wash your handmade socks in a machine, you should still look for washable yarns in order to avoid felting. Socks can felt inside of your shoes when your feet get wet from perspiration or precipitation.
Color. Socks allow you to add a fun pop of color to your outfit, so don't shy away from beautiful colors! Yarns like Sock-Ease even include self-striping options that are really fun to crochet or knit!
Now that I've gone over the important considerations, I'd like to make some yarn suggestions! Of course, Sock-Ease is a great option because it was specifically designed for sock knitters and crocheters. Other yarns to try include LB 1878 (fingering-weight wool), LB Collection Superwash Merino (DK-weight wool), Wool-Ease (worsted-weight wool/acrylic blend), and Cotton-Ease (worsted-weight cotton/acrylic blend).
What are your favorite yarns for making socks? Let us know in the comments!