There seems to be a lot of knitters around now who learn from books or the internet. This can mean you know the how and the ‘rules’ but not why you do certain things. eg. I must knit a tension square/gauge swatch. But why? What is the relationship between your tension and the end result.
Hopefully you are not too surprised to hear that the answer is more than just fit.
Fit is important and it is therefore necessary to check your tension using a ruler to ensure that you will end up with pattern pieces the same size as the pattern. This of course will not ensure a perfect fit as the pattern was written to fit ‘Miss Average size X’ and she doesn’t actually exist. Your waist could be bigger, your back narrower and your bust a larger measurement. Don’t forget the vertical measurements too, the distance from bust to waist varies from Miss X but often that measurement isn’t even provided in the pattern schematics.
The nature of the fibre that you are knitting with plays a big part in the fit of the end of the product too. Silk will relax and grow on washing producing a garment that could be 10% bigger after washing. Wool has good elasticity so washing doesn’t make a lot of difference, mohair and alpaca have slippery fibres so they too will grow in the wash especially if not blended with wool.
Another reason you need to use an appropriate gauge is that yarns are designed to be knitted within a particular range. Yarns have a recommended tension on the ball band. This is not just a guide, it is the tension that the yarn has been designed to be knitted at. If you knit it up a lot looser it will drop and the end product will go out of shape (especially slippery yarns like acrylics and novelty yarns), if you knit it much tighter it will end up being a very dense and somewhat hard fabric (good for socks and toys). Knitting it a bit looser will give more drape and therefore is recommended for scarves and wraps.
So should you knit a tension square? I don’t. I never have and I probably never will. The advocates of swatches say that it saves time in the long run, you will know what tension you are going to get so the garment will fit. But will it? The gauge swatch will give the correct needles to use to make pattern pieces the same size as the pattern. It is the adjustments you make to your size that will give the perfect fit. If you do 10 swatches and always get the same result are you really saving time by repeating the exercise again? They also say that you can’t just assume that the needles you used last time will be right this time. This comes down to practice and consistency. Do you always hold the needles the same way? Do you always wrap the wool around your fingers in the same way and let it slip through on the wrap or do you manually wrap it? Is it a natural movement or are you struggling with the stitches?
I find that my tension doesn’t vary with needles or yarn before washing. If I use a 4mm needle and DK/8ply I will get 22st/10cm. Maybe I am just a freak, maybe it was all the practice and my Grandmother ensuring I threaded the yarn through my fingers the same way every time. This is what tensions the yarn and ensures consistency. I do check my tension, but I do it on the first piece that I knit. I have found it to be incorrect twice in 30 years so I have saved time by not knitting tension squares.
And for the record – yes my knits fit. A tension square does not ensure fit and not doing one does not mean it won’t fit. The tension square just gives you confidence before you start.