When I was a child, I always wanted to taste the rain. Growing up, I learned that rainwater is not allowed to be drunk directly in most cases because it is dirty. Rainwater is one of our planet's most important sources of fresh water. But now researchers at the University of Stockholm have found forever chemicals in rainwater in most locations, including Antarctica. There is no safe space to escape pollution; this is due to the activity of humans. In the atmosphere, there are a lot of aerosols (like dust and fine particles) called cloud condensation nuclei (CCN), which result from human activity and end up in rainwater. The lower the concentration of CCN, the simpler the condensation nucleus will be; therefore, the cleaner the rain and the cleaner the air will be, and vice versa. So rainwater is a medium that can reflect air quality.

I wanted to visualise and record impurities in rainwater. One day after raining, I noticed rainwater stains on the windows, which inspired this project. People seldom take notice of that phenomenon, so I wanted to record images of rainwater stains directly. When people see rainwater stains on the sheets of metal, they will know about the pollution of the air, and it will arouse their awareness of the need for more environmental protection.

I laid out several metal sheets in different locations around London and allowed rain to fall on them. Afterwards, I presented the metal sheets with rainwater stains as a book. Below each metal sheet is recorded the date and place of rain and the PM2.5 and PM10 index of the day. People can read them to check the air quality of rainy days in different areas and at different times. In this project, air quality is no longer only an index of pollution but a visible work of art.