I had a great emailed question today from a lady who is about to get a new machine. She's already enjoying knitting on a simpler machine (the wonderful, affordable Brother 350), and this nice bulky will make it possible to knit heavier yarns and easily make fancy stitch patterns.
Her question was about what tension to use for Aran yarn. Well, she's in UK, where the REAL Aran yarn is available, but I've certainly hand knit with some good "Aran" yarns, or at least I was told that's what it was...Hmm. Is her stuff like the lighter, softer Aran, or is it like the stiff, hard-twist yarn I used once that was thicker? I don't know. But it got me thinking about this whole tension question, and what I've learned about it over the years.
I mostly learn knitting the hard way. I do what doesn't work, repent, and try something different. And repeat. And gradually, I learn all sorts of details that help me out later. This blog is about having them help you out, too, if you haven't yet fallen into some particular error I've experienced.
To me, tension is all about FEEL. The machine should knit the yarn easily, that is, the carriage should slide smoothly across. The resulting fabric should feel good, not packed tight and not sloppy-loose. This means you have to experiment.
The "experimental swatch" has a different purpose from the gauge swatch. For this swatch, you knit a row of contrast for a marker, set the tension dial to a possible setting, knit a few rows, make an eyelet for each number of the dial (so later you can see what tension it was), knit maybe 20 rows, knit another marker row, and try another tension setting. You'll feel the difference with your machine. Ironically, sometimes a looser tension (larger stitch size) will be easier to knit and sometimes a tighter one (smaller stitches) will be easier to knit. You're looking for the "sweet spot" for that yarn. Make a note of what tensions were smooth and easy.
See how photographed experimental swatch gets bigger as it was knitted with bigger dial numbers? Note that I made a section for T3. Too tight. T4. A little too tight. T5 - starting to feel good. So, I did a section of T5.1 (see that extra hole) and T5.2. Finally I did a section of T6.
When the experimental swatch comes off the machine, you give it a vertical tug and let it rest. Then, block it in the way you plan to block the garment. You should launder it, too, whatever way you plan to launder the garment. Yarns can grow, shrink, soften, or fall apart in the wash. Even well-behaved yarns can change size by 10-15%.
You go do something different and return to the swatch with Serene Objectivity, then examine each section and decide which tension is best for that yarn. In case Serene Objectivity isn't living at your house that day (she often fails to show up when I need her), show it to a friend or family member and collect an opinion or two.
The best tension will be easy to knit and produce the look and "hand" you want in the fabric.
If you're doing a pattern stitch, do the swatch in pattern.
Warning: If the yarn is miserable to knit, the carriage hard to push, or too scratchy, or too splitty, or whatever, don't use it in your machine. You can damage your machine, or simply end up frustrated with a very disappointing finished project after investing hours of time and handfuls of money. This goes back to the told truism that a cheapo yarn results in a cheapo sweater. Its true nature will come through, despite skilled, meticulous workmanship. I am referring to quality, not price; some expensive yarns can be disappointing just like cheap ones.