I know we all hate that part. Sadly swatching is essential when designing. Why? Because you need to have a precise idea of your gauge. And even if gauge doesn't need to be exact you, the designer, will need to have an idea to not end with a gigantic ornament or a tiny shawl.
First, you need to decide on the weight of the yarn. You won't knit a washcloth out of lace weight or socks out of bulky, however there's still room for choice. If you have knitted a lot before writing your first pattern, you'll have an idea of your gauge.
Let's take an example: I know my gauge with Rico Design Creative Cotton is 20 stitches x 28 rows = 4" in stockinette on size US7 / 4.5mm needles and 18 stitches x 24 rows = 4" in stockinette on size US8 / 5mm needles, as I've used this yarn a lot in the past.
When designing my Sweet Berries Washcloth, I wanted it to be as close to a 8x8" square as possible so people could easily use it as a blanket square too. Before drawing a draft, I had to find out how many stitches and rows I needed to get the right size. This is where gauge matters. Both 20 or 18 stitches were possible options.
How to decide? It depends on the kind of item. For an absorbent washcloth, better take a tight gauge (but not that tight you end with a stiff fabric either!). Besides with more stitches and rows, there's also more room on the graph paper.
In this case I knew my gauge and the item was mostly stockinette, so I could avoid knitting a new gauge swatch. Now why didn't I prefer DK yarn? Well, I'll answer you honestly. I had that aran yarn in my stash and I like to work with it. There's a moment you'll need to make a personal choice. I designed my first sock pattern to be made out of fingering weight yarn, my second one that's currently being tested will be in sports weight. I've even seen some sock patterns in worsted but I never made any as it's not that cold in my corner of the world, maybe if I lived in Norway or in Northern Canada I'd have a whole collection of thick boot socks.
There are 2 cases in which nobody can avoid swatching:
- You plan to use a yarn you've never used before. Don't guess from similar yarns or from the label. Each yarn behaves differently. If you use natural fibers, whether it is animal or plant based, I highly recommend washing the swatch too. Some yarns grow or bloom weirdly.
- Your stitch is somewhat unusual. Take my Strawberry Smoothie Socks. Where I get the traditional 32 stitches to 4" with my size US2 / 2.75mm bamboo double pointed needles I ended with 34 stitches to 4" in pattern. So this sock is knitted over 68 stitches but has the same finished sized as a 64 plain vanilla sock. My goal was to make it fit a medium woman foot. The knitter can then use smaller or larger needles to make them fit different foot sizes. Colorwork or cables may even lead you above the 70 stitches for medium sized socks.
So, now you have determined the yarn weight and needle size you need to knit your sample. When deciding on colors I suggest you think of one that will do well when it comes to taking pictures later. And of course I can only encourage all knitters to knit a swatch before knitting from someone else's pattern as not everybody knits as tight or loose as the designer. It happened to me to have to go up or down 2 needle sizes to get gauge when knitting from others patterns!