So, the boyfriend was reading my blog last night and asked me what bias was (in regards to fabric). I was like, hmm.
So, I looked it up – and found the greatest tutorial on about.com. You should read it yourself but I loved this handy-dandy stretch test – I think the visuals make it easiest to remember.
The main instances where bias and fabric grain matter is when making binding – and that is really well laid out here.