THE KNITTING world can be divided into those who knit tension squares, and those who don’t, (and those that measure it in the sleeves, which is fine.) Personally, I believe it's crucially important to knit that little square, so it always surprises me when I talk to people who skip this step.
I spoke to a lady recently who was certain the pattern she was following was wrong, because it wasn't the length suggested when she reached the armhole shaping. She said she had the right needles and the recommended yarn, but her work just didn't measure what it was supposed to. I asked the obvious question - had she made a tension square? Her answer was no - she was a very experienced knitter and her stitches were always the right gauge. But how could she be sure that she would knit to the same gauge as the designer?
This is a frequent error among knitters who are keen to cast on, and may not understand the importance of first knitting a square. I'm always really surprised that experienced knitters want to skip this step. Tension squares are often considered boring and time consuming, and although I understand the need to just get going, often making my little swatch will satisfy that urge anyway. Plus, I'd rather know that my garment is going to fit before getting all the way up to the armpits.
This little 10x10cm square will give you so much information about the size your garment will turn out. As a designer, it's absolutely crucial I do this in order for you to knit something the same size that I did.
For instance if I design a garment which I say will fit a 36" bust, it will only fit that size if you are knitting to exactly the same gauge I am. If you are tighter, it will come out much smaller, and as I can't guarantee my knitting comes out to the same tension suggested on the ball band, it's my tension you need to match to get the garment to come out the right size.
It's also important you have the row tension right. That means not cheating and just knitting a few rows! All those little increases that are made throughout the body and the sleeves, x times every x rows, are based on that little square of x sts per cm. Sleeve caps are the trickiest thing to design, as they to fit correctly into an armhole, so unless you are experienced at tweaking this part I would suggest making sure your row gauge is correct before you get this far into the pattern.
It's also worth bearing in mind that your tension will also change depending on what sort of needles you use! Different types of needles can subtley affect both your stitch and row gauge, for example, knitting a swatch on steel needles may turn out differently from bamboo.
All the more reason to knit up that tension square first, I hope you'll agree!
Faye also blogs at Buttons and Beeswax