Digitizing the already-digital

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The coolest thing about knitting punch cards is that they really are just sequences of “yes” and “no”—and that information is actionable in a wide variety of machines, all of which perform different functions based on that information. Some machines can knit two different colors at once—one color is “yes,” and the other is “no.” Others can skip the stitches marked as “no.” Some machines can make tuck or slip stitches, and others still do something called “weaving,” a variation on the aforementioned two-color knitting. The information encoded by these punch cards, regardless of the actual dimensions of the cards, is interoperable across most machines—and when it is not, it is because the number of holes in the punch card doesn’t permit the same numeric repeat (30 and 24 are divisible by a similar, but not identical, set of numbers).

There are a lot of punch card knitting patterns stored on the internet, found in multi-purpose archives like the Internet Archive and in countless community-hosted Google Drives. Unlike a pattern written for hand-knitting, these punch cards are not, strictly-speaking, usable in the format they are stored in. While I could knit a sweater from a set of directions that look like knit 1, purl 40 from an image, working with images of punch card knitting patterns requires a different workflow—one that, counterintuitively, is challenging because of the digital nature of the punch card itself.


Knitting machine punchcards are relatively easy to phone number database in a way that preserves the information, but relatively difficult to digitize in a way that makes the transition back from stored-on-the-computer to stored-in-physical-material feasible. It is entirely possible to recreate a punch card using an image—by hand, laboriously, with a physical hole punch. (Image: Usually I work row-by-row, with a ruler across the image, to make sure I’m putting holes in the right spots and chanting things like “3 yes, 1 no, 3 yes, 4 no” in repeating patterns. It is error-prone, but consistent with how generations pre-internet worked with these patterns—translating an image in a book or magazine into binary data of “punch this, not that.”

However, those with more patience for debugging than patience for tedious card-punching have been experimenting with a variety of methods that allow for computer-controlled punching—or, more often, cutting that imitates punching. The Cricut is the standout piece of hardware here, although any machine that can precision cut paper using code will do. These machines, called CNC machines (CNC stands for “computer numerical control”), can have laser or blade attachments, and they work the same way as the massive plasma cutters used for cutting steel. A layer of software, which can be open-source or proprietary, translates an image stored as a SVG (scalable vector graphic) into strings of numbers that control the cutting head.