At the end of the 19th century the original vermillion was superseded by the red cadmium pigment, which in addition to being better for one’s health is also more durable. The mercury vermillion would in time lose its colour intensity due to chemical changes. Recent research has shown that this occurs in two phases under the influence of the chloride present in the air. First of all, very tiny amounts of chloride combined with light to produce globules of metallic (pure) mercury that are visible on the painting as black patches. This mercury then reacts with the remaining chloride resulting in the black changing to white. This causes old vermillion layers to change colour and exhibit white and black patches. What's more, they could not be mixed with the then lead and copper-rich pigments such as white lead, chrome yellow and verdigris. Due to efforts to protect the lucrative trade in expensive mercury vermillion, it took quite some time to get the practically identically-coloured cadmium pigment onto the market. As cadmium is also harmful to the health and environment, albeit to a lesser degree, these days the colour vermillion is produced on the basis of harmless, stable pigments.