The Music Mural

Conductive paint can turn just about any surface into an interactive playground

By Alice Zhang

Here’s a behind-the-scenes look at how Alice Zhang made the conductive mural that has wowed visitors over the last year. Careful, reading how she made this installation may inspire you to create some audio-visual art for yourself!

Over the course of six weeks, I’ve had the pleasure of working on “Conduct San Jose,” an interactive mural that plays sound when you touch it. It works using conductive paint coded to act as touch sensors.

“Conduct San Jose” responds to touch with various sounds and music.

Although the project appeared complex at first, I was glad to find an assortment of resources online and a wonderful team in-person that helped me immensely. It was my first time learning to build circuitry, making art on such a large scale, soldering, using epoxy and experimenting with different microcontrollers to make conductive materials into capacitive sensors.

All of these processes seemed daunting before I began, but this project helped me realize that these skills were never inaccessible. Anyone who wants to create an interactive project with conductive paint can learn to do so, and I highly recommend if you’re interested to try it yourself!.

The most challenging aspect of the project was the scale of the mural. “Conduct San Jose” is 8 feet tall and 16 feet wide, making it the largest art piece I have ever attempted. The conductive paint patches were also large, and triggered more inconsistently than smaller patches. For reference, Bare Conductive’s tutorials feature conductive paint patches around 10 inches long. The patches on “Conduct San Jose” were up to 5 feet.

Alice Zhang illustrates how she created the mural.

To make the conductive paint sensors trigger more consistently, a series of decisions were made:

• The paint patches were filled with a striped pattern instead of a solid fill. This pattern gives the electric charge a path to follow instead of spreading out along a plane and results in greater consistency.
• Instead of using microcontrollers we already owned, we decided to purchase the Bare Conductive touch board. Bare Conductive claims its board is more sensitive and triggers more consistently compared to an Arduino board.
• All of the connections had to be soldered. The mural did not work when copper tape was merely overlapped and not soldered.
• The threshold for triggering a sound had to be lowered.
• Capacitive sensors work by finding a background capacitance (an ability of a material to hold charge) and then sensing changes in capacitance. Since larger patches have a larger background capacitance to begin with, they are less sensitive to changes in capacitance and tend to sense more noise.

The touch board made the coding aspect of the mural far easier, since the board is precoded with example sketches that can be edited using the Arduino IDE. The only changes I had to make was to the thresholds and instrument sounds. However, I also experimented with using the Arduino UNO and Makey Makey boards, and found this Arduino capsense library and this Makey Makey capacitive touch tutorial to be useful.

For anyone who already owns these boards, a capacitive touch project is within reach and can be done with more than just conductive paint. A quick online search will show that people have successfully made interactive projects with fruit, water, pencil drawings, plants and just about anything that can conduct electricity. People have also used conductive paint to do more than just play sounds using a flat surface; they have made light switches, projection mapping projects and even 3D painted surfaces. With some imagination, the possibilities are endless!