In 2009, a conservator discovered an abnormal phenomenon happening to a Chinese opera troupe collection stored in the Heritage Conservation Centre (HCC): silvery droplets were dripping from the painted surface of a wooden ruler and a decorative opera sword. A qualitative chemical spot text was carried out on the droplets, revealing the presence of mercury. Mercury is highly toxic. It has a low melting point and quickly turns into liquid and vapour at room temperature. This heightens the risk of mercury entering the body by inhalation or through epidermal contact. Our investigation on detecting mercury in objects would be the first of its kind done in HCC. A preliminary plan was laid out in 2010. Our research aimed to reveal the risks that practitioners face when dealing with hazardous objects – in this case, items with mercury – and to put in place safety measures for them. The process of our investigation primarily comprised surveying the entire opera troupe collection to identify and segregate objects suspected of containing mercury. This was done in two ways: through chemical identification method, and via qualitative analysis using a handheld X-ray fluorescence (XRF) machine.