Zeitfluss [flow of time]

Reasoning about time by printing onto the surface of a river

Maybe you know situations when time's running up. In German there is a metaphor for that and translated it would be something like „time trickles away“. Having this saying in mind and thinking of how to 'imagine' time the following idea turned up:
I would like to generate a situation, where people are able to let time pass by without getting into a hurry. Therefore the digits of time get printed onto the surface of a river with food colouring, so time could be observed from a bridge in peace, while it trickles away.
This idea got realized September 2013 in Innsbruck, Tyrol.


The time is trickling away

The printer mounted below the bridge; ready for printing.

the river printer

The video above is showing parts of the printing process and the resulting time on the surface of the river. Below a time lapse video of the last 20 minutes the installation was running.


Where it took place

The “Karwendelbrücke“ is a bridge a bit offside from the center of Innsbruck. At the top trains are crossing the bridge and beyond pedestrians are walking from the outskirts into the center of the city and contrariwise. People cross the bridge mainly on their daily routines.
Here images of the location from November 2011 till May 2013 - the periode of time it tooks to get the permission:

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place 2011/11 place 2011/12 place 2012/09 place 2013/05

The elements for printing onto a river

pixelgrid and pump

The digits are printed in a 7x5 pixel resolution. For every vertical row of a digit there is one micro piezo pump that generates the drops. Therefore the pump controller gets switched on and off depending on how long it takes the pump to produce a drop. In fact the water surface is used like a sheet of paper in an inkjet printer: One vertical line of drops gets printed - the water flows further - another line gets printed; and the numbers occur.

disolving colour

The black drops consist of distilled water (90%) and food colouring (E151, 10%); besides printing onto a river it is used to colour marzipan or caviare. Above a test how strong the colour takes effect. Roughly 70g a day were used for printing the time once every minute within six hours.


Hardware and electronics

The sketch is showing which stuff is involved and how it is connected to generate the drops and to monitor, if the installation is operating.

electronics and hardware sketch

The core element is an Arduino. It receives the current time trought a Real Time Clock Module. The micro controller maps the numbers of the time onto the available 5x7 pixel grid per digit. The resulting vertical lines of drops get printed one after the other by switching the shift registers and thereby the pumps. The Arduino code and the wiring diagram were done by Albert Frisch and could be found on the projects site on GitHub.
For logging what's going on, a RaspberryPi receives status messages from the Arduino. Once in a while - on an average every 20min - fswebcam gets called and takes webcam images as fast as it can for about 40 seconds. Afterwards the images plus log files get uploaded to a Server with fixed domain via a GSM-connection. All the input and output gets processed through a node.js Server; hence it is possible to serve a website on the Raspberry Pi as interface (with usage of websockets) for the installation that could be accessed via Ethernet and a modern browser on the footbridge.

webcam images for status check

One issue was power connection on the bridge. The train was ahead of the installation, but 5V ... The solution was to go for solar power to drive the installation on its own. Two panels (each 10W) in combination with a charge controller and a lead storage battery are used to provide the needed power.
Below a video of the test set-ups: LEDs were used instead of the piezo pumps to simulate the printing of all four numbers in one row (e.g. 02:01); and the pumps on a dry run.


Details on the construction

The sketch and the image below are showing the installation from front.

sketch of construction construction from front construction from side

For further information

Just get in contact.


Supported by: Albert Frisch (electronics), Franz Schwarz (chemistry), Martin Grödl (programming).
Funded by ,