Three days in August, and the doors of our Beijing studio stayed open from nine in the morning until the light outside gave up. We pushed the benches against the walls, swept the brass dust out of every corner, and set the lamps where people could reach them: low tables along the windows, the tall floor pieces in the middle of the room, the small ones on a shelf at hand height, so that anyone could switch one on without asking.

An open room is harder to light than a finished one. Nothing hides. We ran the pieces at three levels — a warm glow along the window wall for the afternoons, the working lamps over the benches for the demonstrations, everything else held back until evening. Around seven we turned the ceiling lights off and let the collection speak for itself. That is the hour people remember. As one of our bench hands put it at the end of day two: you can explain a lamp for ten minutes, or you can put it in someone's hands and let them find the weight of it. The second way is shorter.

What the three days held

• A maker at the vice each morning, bending, filing, answering whatever was asked.
• The paint room, opened in short visits, with thin coats and earth pigments laid out on test panels.
• A long table of prototypes: half-finished forms, rejected shades, and one lamp we still argue about.
• The evening hour — ceiling lights off, every piece switched on, conversation lowered to match.

Visitors came for an hour and stayed for four. Architects arrived with plans folded under their arms and unfolded them on our table. Students sat on the floor with sketchbooks. A man who bought a small reading lamp from us years ago brought it back in a cloth bag to show us how it had aged; the patina on its base had gone the colour of strong tea, and no hand of ours could have planned it better.

By Sunday the shelves were half empty, our voices had gone, and a fine brass dust remained on the floor that no broom would fully take. We count these days in questions, in the ones people were brave enough to ask while a lamp stood switched on in front of them. Design Days returns next August, with the same benches and the same open doors. Light is easiest to explain with the lights off.