Choosing the right yarn

I'm a big believer in learning from mistakes! Fortunately I love learning and with Crochet there is so much to learn.
I've just made a leap forward in my understanding of how to approach yarn thanks to Dora Ohrenstein. If you want to make garments you should rush out now and get a copy of  Top-Down Crochet Sweaters. Don't buy it for the patterns, although they're great, buy it for the wealth of experience Dora shares.

Fibres 
We've already talked about the different qualities of different fibres; softness, stiffness, fluidity and flexibility. A garment made in cotton will be stiffer and heavier than if it were made in Alpaca. There will even be a difference between animal fibres.

Weight
Yarn weight usually refers not to the weight but the thickness of the yarn. At size 3 (usually DK weight) this is a yarn which when crocheted produces a gauge of 12 to 17sts per 4inches when using a 4.5 to 5.5mm hook. So you can see that this is a wide range of thickness. 

Weight
So now we need to consider the actual weight of the yarn. I could replace an alpaca yarn with a cotton yarn that crochets up to exactly the same gauge but it will give me a different garment in look, feel and drape. If I were to use the cotton yarn the actual weight of the garment would be much heavier. You can imagine that with wear my pullover would hang lower, be longer, and probably be tighter; because the weight is pulling it down.

Twist
As crocheters we often complain about yarns which split easily. A yarn which is tightly twisted will be very strong and stiff. It will probably give great stitch definition. It will be great to use on doilies and perhaps Amigurumi, but on a garment it may not give me the drape and flexibility I'm looking for.

Plies
If you pull apart a length of yarn you may find that it is made from bunches of yarn, or plies, which are twisted around each other. Thus we get 2-ply and 3-ply etc. If the plies are very obvious it may distract from the beautiful stitch pattern you are creating. However if the yarn is very loose it may be difficult to work with. A single-ply yarn should not be avoided however. What we are looking for is a yarn that is smooth and will show off our beautiful work.

Fluff
Fluffy yarns produce a different look again and perhaps this is what you want in your cuddly winter pullover. You won't see the detail of stitch but if what you want is a light weight (on the scales!) garment with lots of drape this will be great. I've found that very open mesh and lace stitches can take on a completely different look when using a softer yarn which is left unblocked.

What I have learnt is that I should never rush off and buy a yarn for my stash just because I like the look of it! I should always have a project in mind. I should have already considered what look I want to achieve and then I should buy just ONE ball. Really? I need to crochet up a gauge square and wash it and block it before I go any further. It does sound rather dull but unless I want to keep creating disasters, this crocheter needs to learn some discipline!!