What seams like forever ago I asked a question on my Instagram feed about shoulder seams. Unsurprisingly, people seemed to have a strong preference. Also unsurprisingly, their preferences were all over the map. But it did raise the question: is one method of shaping and joining shoulder seams inherently better than the other? Does one provide more stability? Is there a reason to favor one over the other aside from personal preference?
If you’re new to sweater construction let me explain (if you’re not, feel free to skip the next two paragraphs). Your shoulders are not flat. Depending on the type and fit of sweater you’re knitting, if you want it to fit properly you need to create a slope in the shoulder area.
In bottom-up sweaters, there are two main methods for shaping shoulders and joining them together. Traditionally you would bind off a few stitches on successive rows creating a shoulder edge that looks like a staircase. The staircase from the front shoulder and the staircase of the back shoulder are then seamed together. The other method involves creating the slope of the shoulder through a set of short-rows and then joining the live stitches from the front and back shoulders through the 3-needle bind off.
Enter my experiment. All things being equal, I wanted to see how each type of shoulder join would handle abuse and hold up over time. I dug through my stash for the heaviest yarn I could find and knit four identical shoulder pieces with it. Two were shaped with stair-step decreases and seamed together. The other two were shaped with short rows and and joined via the 3-needle bind off.
If these don’t look identical to you, it’s because the 3-needle bind off over live stitches takes up more room vertically than does seaming together bound off stitches. I measured and weighed the swatches and then sent about testing them, making sure to always compare the growth of the swatch and seam to its original measurements.
First I hung them dry over a clothes line with 1 kg of weight suspended from the swatch (half from the front and half from the back) to simulate the weight of a larger bulky sweater pulling on that seam as its worn. After two days I took them down, measured, and wet blocked them again. At this point there was no difference in percentage growth between the swatches.
Then I really tried to abuse them. I wet blocked them again and hung them weighted over the clothes line before they were dry. I took them down, measured them again, and then wet blocked them. Again, there was no difference in growth between the two. More importantly, there was no difference between the two in terms of growth at the seams.
What I conclude from this is that the two methods will hold up similarly over time and abuse so go ahead and use your preferred method guilt free.