Fading Domes: Thermochromic Painting

An interactive painting with thermochromic pigment and resistive wire.

Three resistive wires are shaped into an
engraved sheet of Perspex, forming the perimeters of three famous Italian domes (San Pietro and Sant’Ivo alla Sapienza in Rome and Santa Maria della Salute in Venice). These are then connected to a battery through three buttons that interrupt the circuit.

Once the buttons are pressed the energy flows and heats the resistive wires, which are placed directly behind the thermochromic ink layer, heating the pigment and thus changing its color.

Project and execution by Sofia Aronov

Resistive wire is difficult to shape so, to give it the form of the 3 domes, I first engraved their perimeters into a clear acrylic sheet: this provides a 1 mm bevel that is a useful guide to fix the wire path into.

The top layer, what will be the "canvas" of the painting, is coated with thermochromic pigment through screen printing: this provides an homogeneous/even surface which is difficult to achieve by directly painting the ink on paper.

To screen print it is necessary to mix the pigment with a transparent medium.

Once the ink is dry the paper must be cut in the right size and the three LilyPad buttons fixed in position (with thread or double sided tape). The buttons are then to be connected to the rest of the circuit using conductive thread of jumper wires (soldering in this case): these are suggested because more resistant and easier to connect to the resistive wire. In fact, resistive wire rejects solder: the only way to connect it is then to wrap its extremities around the ones of the conductive wire. Otherwise crimps are an option, although less resistant.

The resistive wire requires a a considerable amount of voltage to heat fast enough. This is why I connected each resistive wire path to 2 9V batteries linked in series. This provides enough heat for the painting to work efficiently and fast. Although the buttons control the flow of energy it is a good rule to always disconnect the batteries once interacted with the painting: this is a big amount of volts and it is important to be careful in handling it.