Interactive Wall Murals

Scale changes everything

A small paper instrument is one thing. A wall-sized mural where visitors touch painted shapes to hear sounds is a completely different experience — it’s spatial, public, and invites exploration in a way that a tabletop instrument doesn’t.

The Touch Board hardware doesn’t care about scale. The same 12 electrodes and the same code work whether the painted area is 5cm or 5m. But physical scale introduces practical challenges: longer traces, more resistance, more exposure to humidity and handling.

Surface preparation

Designing for scale

Plan on paper first. Sketch the layout at scale, noting:

• Where each touch area (shape) is
• The routing of traces from each shape to a central point (where the Touch Board will be)
• How traces will avoid crossing each other (crossing traces = short circuit)

Keep traces short where possible. Longer traces = higher resistance = more potential for false triggers or missed touches. Aim for traces under 1m where the mural layout allows.

Trace separation. Leave at least 10mm of uncoated wall between adjacent traces for large-scale work (vs 5mm for paper).

Painting large electrodes

Large electrode areas (hand-sized or bigger) need thorough coverage:

1. Apply first coat — fill the shape completely
2. Allow 30 minutes to dry
3. Apply second coat — this dramatically reduces resistance
4. Check resistance between the shape and the end of its trace: target under 200 kΩ

For very large areas (A3+), use a wide brush or small roller. Multiple passes with overlapping strokes.

Routing long traces

Long trace resistance is the biggest challenge. Solutions:

Option A: Add copper tape over the trace. Paint the trace, let it dry, then lay copper tape along the same path. The copper carries the signal; the paint provides adhesion. Clip to the copper tape at the end.

Option B: Use copper wire. Hot-glue or tape thin wire along the trace path. Paint over the wire to hide it. The wire carries the signal at near-zero resistance.

Option C: Use a hub approach. Place the Touch Board at the centre of the mural, not at one edge. All traces radiate outward like spokes — none longer than the radius of the mural.

Where to put the Touch Board

For a permanent wall installation:

• Mount the Touch Board behind the mural in a recess or on a small shelf
• Route cables through small holes in the wall if necessary
• Cover the board with a protective enclosure (see Intermediate article 07)
• Leave a small access panel for the USB and SD card

For a temporary installation:

• Fix the board with removable adhesive on an accessible surface nearby
• Route cables along edges or under baseboards

Speaker and audio placement

Sound placement matters as much as touch placement for a good mural experience:

• Hidden speakers behind the wall — requires wall access, best effect
• Small speaker mounted beside the mural — practical, not hidden
• Directional speaker mounted above — focuses sound at the mural area
• Bone conduction via the wall surface — experimental; requires a transducer glued to the wall

For multi-zone murals where different areas should play from different locations, the Touch Board’s single audio output limits you to one location. Consider multiple Touch Boards (Intermediate level) or a USB audio interface with a computer for positional audio.

Protection and longevity

Electric Paint on walls is durable but not indestructible:

• Varnish — apply a clear acrylic varnish over dried paint for waterproofing and abrasion resistance; test that it doesn’t reduce conductivity first
• Protective glazing — for high-traffic areas, Perspex sheet over the painted surface; sensing works through up to 3mm
• Rope or barrier — guide visitors to touch specific areas, not rub across traces

Key takeaways

• Surface preparation (sealing) ensures Electric Paint adheres and conducts reliably
• Long traces need copper tape or wire reinforcement to keep resistance low
• Place the Touch Board centrally to minimise trace lengths in all directions
• Two layers of Electric Paint reduces trace resistance dramatically
• Leave 10mm between traces for large-scale work to prevent cross-coupling
• Varnish over the paint for durability in high-traffic public settings