A bathroom wall at New Wave Coffee Credit: Leor Galil

You can tell a lot about a place of business by its bathroom. Are the facilities pleasantly lit, or are they so dim you can barely see the outline of your own body parts? Is the air laden with perfume that smells better than anything you’ve ever worn on your own body, or does it make the word “foul” seem inadequate? Is it a room where you feel comfortable enough to rest, or would you rather, um, evacuate? As important as those questions are, I’m usually less interested in what the proprietors bring to the bathroom and more in what they allow their customers to leave—and by that I’m referring to graffiti.

It’s not as though I make a special trip to the bathroom in a coffee shop, bar, or restaurant just to look for graffiti. But if there’s something scrawled on the wall of a toilet stall or next to the mirror above a sink, in order to read it all I’ll often linger past the point of politeness. (Apologies in advance if you spot me staring at a bathroom wall.) I’m drawn to all matter of public, noncommercial media, be it a piece of street art wheat-­pasted on the side of a building or a flyer in a bookstore asking me to be friends with the stranger who made it. But bathroom graffiti is different. It’s intimate, often mischievous, sometimes repugnant, and frequently surprisingly conversational.

By “conversational” I’m not just referring to the way strangers reply to one another’s quips or take a Sharpie to an anonymous one-liner to change its meaning—there’s also the way every little doodle and homemade sticker seems to fit together into a big, messy whole. There’s rarely much cohesion, and the total effect is usually less “art” than it is “lots of ink”—the hodgepodge of handwriting in the men’s room at Cole’s, for example, has grown into giant splotches and rays of black marker. But take a closer look, and eventually you’ll get a sense for what the patrons of a particular place care about, what they think in their moments of solitude, and which things in their lives leave such an impression that they’re driven to make a mark in a place that isn’t theirs.

All these little notes, stickers, and curious drawings represent the collective psychological weight of those who have passed through a particular bathroom. And they can offer some insight into the culture and history of that part of Chicago. On a recent visit to Filter in Wicker Park, I found stickers and little pieces of art on the mirror and door of one of the coffee shop’s three bathrooms. Say what you will about gentrification in Wicker Park—I certainly have—but that graffiti made me feel at home. Near a “Rock & Roll McDonald’s” tag (a tribute to Wesley Willis, I assume) was a USPS Priority Mail sticker adorned with a drawing of an orange floppy disk whose label read “ENLIGHTENMENT DISK 1 OF 8,128,396.” In its surroundings, it all makes sense.