There's nothing more frustrating then discovering a knot in your yarn especially if you don't find it until you are part way through a row. I have to admit my heart sinks every time a customer says to me I'm not complaining but that yarn I bought last week had knots in it.
Firstly the yarn is not faulty, the yarn manufacturers don't consider the yarn to be faulty unless there are more than 3 knots in a 100g ball of yarn. In a minute I will explain how to deal with those pesky knots but in the meanwhile lets just discuss how they end up there. If you have a ball with a lot of knots in or found parts that aren't spun or not spun as tightly as the rest then its faulty, bring it back and we will swap it.
Most yarns are mass produced especially the lower end yarns and in order to avoid wastage when the yarns are spun in the mill if they find a break they simply knot it and carry on. For most yarns this isn't disastrous but for the self striping yarns or the self patterning yarns this can cause a bit of a problem. Your hand dyed yarns tend not to have knots in as they have been examined as part of the dyeing process, hand dyed skeins with knots in tend to be sold as seconds. Your higher end yarns where they are producing less for example West Yorkshire Spinners tend to have higher quality control and you are unlikely to find a knot in these yarns. It's not impossible just more unlikely.
Let's face it having a knot in the middle of your knitting is pretty disastrous, I've seen these knots unravel to form a hole when the garment has been washed it's not a pretty sight. First off make sure you unravel your yarn before you start a row and make sure there are no knots coming up, it's far easier to deal with it now then in a middle of a row. If you do find a knot cut your yarn leaving a tail long enough to sew in and rejoin your yarn after the knot. The bit you have lost will do for sewing up it won't go to waste.
If a disaster does strike and you find a knot mid row we can sort it you don't need to pull a full row back. I personally would cut the knot out and rejoin with a russian join this will only work with yarns with a wool content if it's all acrylic forget it. If it is an acrylic yarn then you will need to use a magic knot to join it , I know we said no knots in the middle but at least if you knot it you know its been done well.
For self striping yarns and self patterning yarns the same principles apply but you might have to unwound quite a bit of yarn to get it back in the right sequence. Don't panic at this part the yarn you've unwound will come in handy for the bands or sewing up it won't have to go to waste.
Of course if you need anymore advice just call into the shop it's what a Local Yarn Shop if for.