The 21-Centimeter Pillow

Pillow embroidered with hydrogen's Balmer lines.

This was my last project of 2013: a pillow embroidered with the lines of hydrogen’s visible emission spectrum. It’s one of the projects I’ve had on my to-do list for nearly half a year, and when I finally had some downtime after the flurry of finals and Christmas, I jumped at the chance to cross it off my list.

The pillow was secretly a birthday present for my little sister Helen, who’s an aspiring astronaut. While I wouldn’t ordinarily give a 15-year-old a throw pillow for her birthday, she’s in the process of re-decorating her room, and the design on the pillow is the Balmer series, or the visible part of the hydrogen emission spectrum.* Because this emission spectrum is a fundamental property of hydrogen, it can be used to figure out the composition and age of stars, to identify objects like black holes and binary stars, and to map galaxies.

Wisconsin H-Alpha Mapper Northern Sky Survey

Though the emission spectrum isn’t the only interesting property of hydrogen, it’s a surprisingly powerful tool for astronomers and cosmologists, and it’s given us a staggering amount of information about nearby stars and exoplanets. (And, of course, it allows astrophotographers to take pretty space pictures, which is a noble cause in itself.)

Embroidery floss and fabric, pre-pillow.

The pillow took surprisingly little in the way of materials; the most difficult part was being patient enough to finish the embroidery in time to give it to Helen for her birthday. (I went through a lot of episodes of Wartime Farm making this thing.) I used a 12″ x 21″ down pillow from West Elm as the pillow form, and found a basic black cotton fabric at Joann’s. All of the embroidery floss is DMC six-strand floss, also from Joann’s; the colors are, in order, Very Dark Blue Violet (333), Dark Cornflower Blue (792), Light Peacock Blue (3766), Dark Electric Blue (995), and Bright Red (666)*.

I started out by making a 12″ x 21″ template out of posterboard, tracing that onto the fabric, marking a 5/8″ seam allowance around the outside, then cutting two pieces (a front and a back). I set the back piece aside and used GIMP to fit an image of the Balmer spectrum to a 12″ x 21″ rectangle, so I could figure out how to space the embroidered lines. The lines ended up being 1.12″, 1.76″, 2.77″, 5.15″, and 12.61″ from the left edge, or 1 and 1/8″, 1 and 3/4″, 2 and 25/32″, 5 and 5/32″, and 12 and 5/8″ in units you’ll actually find on a ruler. (I did actually mark the line placement down to the 32nd, because, well, engineer.)

Image of stem-stitched embroidery on black cloth.

The whole piece is worked in stem stitch, which spirals nicely and makes the lines look like solid bands from a distance. I used all six strands of floss to do the embroidery; while this made the fabric pucker noticeably, the puckers ironed out in the end, and the relative bulk of the thread gave the lines a very nice raised texture.

Once the stitchwork was done, I pinned everything together, sewed around three of the edges, and stuffed the pillow form in. Only as I was preparing to sew up the last edge by hand did I notice that I’d conveniently managed to leave the selvage, or self-finished edge, as the unsewn one…so I decided to leave it as is and tell Helen that she could either keep it as a removable pillowcase or finish the edge if she wanted to. (I am, if nothing else, spectacularly pragmatic.)

For a few hours of work as a way to wind down over Christmas break, I’d call this a rousing success — Helen loved it, it coordinates beautifully with her newly Mars-themed room, and I really enjoyed being able to make something without needing to break out the power tools. Now I just need to find a way to top this next year…

* The dark purple line farthest to the left is technically in the ultraviolet range, but, um, artistic license.

** I still have no earthly idea why they didn’t call this color Devil Red.

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