Printing the World’s Largest Receipt Paper Mural
Davis DeWitt created what is likely the world’s largest receipt paper mural — and you can, too.
A popular joke on the internet is that inkjet printers don’t work reliably, despite the technology having decades to mature. But have you noticed that receipt printers don’t have the same problem? They chug along in countless businesses around the world with only occasional issues. Davis DeWitt took advantage of that reliability to create what is likely the world’s largest receipt paper mural, and you can, too.
Receipt printers are reliable because they’re very simple. They don’t contain any ink or toner, instead relying on the receipt paper itself. That paper has a heat-sensitive (thermochromic) coating that darkens when hot. The receipt printer’s print head contains tiny electronically controlled heating elements in a row, which get hot to match the pixels of that line of the image. They change temperature fast enough that the printer can shoot out receipts at a respectable speed — something DeWitt was certainly thankful for when tackling this project.
His mural covers an entire wall, with the print image being an insane 8560×3276 millimeters at 300 DPI. The image is a map of Los Angeles in vector format, which let DeWitt scale it up to that resolution without the pixelization that would have made a raster image unsightly at this scale. DeWitt struggled to find software that would even work with that resolution and ultimately settled on Adobe Illustrator for modifying the vector image and Adobe Photoshop for exporting it as a PNG file.
From there, DeWitt used open source software called ImageMagick to slice that huge PNG file up into a bunch of skinny vertical strips suitable for the receipt printer. That slicing process alone took several hours and that was before DeWitt even started printing.
But eventually, DeWitt had a big stack of receipts that, when placed side-by-side, would form the gargantuan mural. There was only one problem: the receipts wanted to curl up and that wouldn’t look very good at all.
To solve that problem, DeWitt made a motorized roller contraption that spools up the receipts in the opposite way. That removed most of the curl, but didn’t eliminate it completely — it also didn’t stop their inherent tendency to flap and flutter in the slightest breeze. The tops of the receipts were pinned to a horizontal strip of wood, so DeWitt attached binder clips to their bottoms. He then ran a fishing line through those and anchored the ends onto 3D-printed brackets. With the fishing line wound tight, it keeps the receipts taut and straight.
The resulting mural looks great and the best part is that you can follow DeWitt’s lead to make your own murals. If you get tired of one, you can easily print another to replace it. Neat!