All mediums that use yarn have different requirements of their materials. However until very recently, most yarns were made solely with knitting in mind, (Exceptions being warping threads/yarns, needlepoint and crewel threads, tatting and cotton crochet threads.) yet in regards to crochet we have far different needs and requirements to produce flexible, supple garments.
Often the best knitting yarns do not produce even close to the right effect in a crochet project, especially when a straight yarn is used, and the emphasis is upon technical stichery.
To improve your crochet projects (especially in sweaters and socks) look for yarns that have less twist in the ply. The looser the ply the better it will work as a flat piece, offering more suppleness and if drape is required this will be a huge factor to your crochet project.
For a good work horse for crochet felting projects, I like Cascade yarns’, Cascade 22o. It’s a little lighter on the twist, and felts up like a dream. It is not expensive, and comes in a multitude of colors. I don’t know that I would do a sweater out of it in crochet, unless I used motifs.
Choosing the right yarn is important. Remember we add twist to the yarn when we crochet, and that is why many projects end up being like bullet proof vests! You can either go up a hook size if you are like me and have waterproof tension, or go with a finer yarn. Remember, you don’t want the perfect knitting yarn for a crochet project.
For example, the yarn pictured above is fantastic in crochet projects! It is awful to use for knitters. Why? It has zero balance. Only two knitters I know have been able to knit with this yarn at all. Crocheters love it! It’s like a new toy!
Knitting takes out twist, crochet adds twist. Weaving in general leaves the yarn even as it was made.
Just some basic information that can make or break your project.