I have been on a quest to be a able to spray-paint QR codes, in mass production. I recently demoed my QR code stencil work at Maker Faire.
The secret, in short, is chicken wire and caulk.
I tried the following methods unsuccessfully:
- cardboard cutouts (subject to the island problem)
- suspending wires across a board and using duct tape (suspending wires takes too long, duct tape moves when covered in spray paint)
- using very large chicken wire and using foam blocks to plug the wholes. (far far far to time consuming, but theoretically should work resulting in a massive QR code about 1 meter x 1 meter)
- using a very small hole circular whole punch on paper (subject to the island problem, but less so)
The first thing that I got working is using very small chicken wire, and using caulk to bridge the gaps between the parts of the wire required to block the spray. This seems to work. A picture, as they say, is worth a thousand words.
Pretty simple see! Now, once you have created that stencil, you can use black spray paint to create a readable QR code on anything you -own-
Tips for creating the stencil:
- Create a printout of your QR code that is exactly the same size of the QR code (I did not think of this. Karen Herzog figured out after two seconds of thinking about it)
- Print the QR code on really thin, flimsy paper if you can.
- Lay the QR code down, and lay the chicken wire over it.
- Caulk anywhere there is white (ie. so that the black will spray through)
- Let dry overnight.
- In the morning, you will find that the paper is also caulked
Suppose you do not own the thing in question. There is still hope. To create somewhat more legal QR code graffiti, you can create a reverse stencil (i.e. instead of putting caulk to block black spray paint, you use a negative stencil to block white spray paint). Then you can use white chalk spray paint against a dark surface. Remember that the QR code standard requires a “field of white” around the QR code, so using a reverse stencil you have to be careful to spray generously around the QR code too.
While at Maker Faire, I bought a hoodie and used this method to spray paint chalk on it. You can see the results below.. it still scans!!
For those who prefer to watch the action first hand…
Here is a video of how the reverse chalk spray works on asphalt
Here is a video I made b/c I was losing my voice that basically shows what I was doing with QR codes at Maker Faire.