OK folks, I measured before and after. Paper does indeed shrink when it is ironed. Even the fancy “paper piecing” newsprint-style paper whose manufacturers claim it won’t shrink and curl. But here’s the kicker: it seems to go back to its original size after cooling down.
This week I needed some airplane blocks, and paper piecing cropped up again. I had to choose between fussy templates, free-form plane blocks that would each be a little different (sorry, this layout will look better with uniform blocks) or the not-so-favourite paper piecing.
What drives me nuts about paper piecing is that sometimes things don’t line up where they should, even though precision is the whole point of paper piecing. If I sew exactly on the lines, things should be just the right size in just the right places and should line up just so when I join up pieced sections. That word “should” definitely doesn’t mean “does”.
While I was trimming along the printed seam allowances for the pieced sections of this plane, I noticed that the lines were not where I expected them to be according to my ruler. The section was a rectangle, and should be 6” long, or 6 1/2” unfinished. It was 1/16 of an inch short. That’s small, but it adds up, and because the shrinkage was greater in one direction than the other, it messed just a bit with the aspect ratio of the design.
Today I printed the paper foundation and measured. It was exactly the size it was supposed to be. Then I ironed the paper and measured again. Ha! It did shrink! Can’t blame it on stitching puckering the paper, or any such thing, because there was no stitching yet.
You can see I lined up the 1” mark on the ruler with the same line in both pictures, but that dark line on the far right is at the 7 1/4” mark before pressing, but about 1/16th less after ironing.
And, just to mess with my mind, here is the same paper after it has cooled and relaxed for about an hour.
Really? It’s back to the size it should be. I tried this with a plain 3” square too, and got the same shrink-unshrink result. Clearly there is some physics of materials at work here. I really don’t feel liked dusting off my physics degree (I do have one) so here’s what I am going to do: I will sew one seam at a time on my paper pieced units, and wait a nice space of time for the paper to cool and relax before I go sew the next seam. Then I’ll see if my pieced sections end up the right size and line up “just so”.
While I wait for things to cool, I’ll just stitch up these cute little framed nine-patches for my alternate blocks. These are NOT giving me any grief!