Pee to Check-In to Foursquare - Mark Your Territory

Step 3 Create the Markers (Printing/Cutting)

These markers do more than just get peed on; they feature carefully designed affordances for claiming territory in hybrid digital/physical spaces.

At their core, they can stick in the ground and illustrate text and QR codes. The needs to be only revealed if it gets peed on well enough though. Let's see how to make this.

First I tested out various methods of getting an image to show up when wet (crayola color changing markers, litmus paper printing, wax burn-off). You can see the excellent full brainstorm discussion at
http://www.instructables.com/community/Secret-Message-Revealed-After-Wet/

Eventually i went with the spraypaint/laser cuttter/ soluble gouache method as it produced the results with highest contrast.

Get nice thick rigid (yet absorbent) paper. I used water color paper.

Give a thin, even dusting of spray paint on one side.
Load up your design in illustrator ( the stencils I used are available here: http://dwig.lcc.gatech.edu/projects/Quitmeyer/myt/store/Mark_Your_Territory_Illustrator_Stencils.zip )

Now when you laser cut onto the spray painted paper, it will cut through the thin layer of paint on top and reveal an inverse image of high contrast (and nice physical texture).