Some lead-glazed ceramics of the Han dynasty in China, Persian ceramics, and ancient Egyptian glass have a beautiful and mysterious silver color due to alteration. This phenomenon is called silvering, but it does not mean that silver has blown out.
This is because when glazes and glasses are weathered for a long time and divided into thin layers, air enters between the layers, which refracts and disperses the outside light, causing the opalescence phenomenon. This phenomenon occurs not only with lead glazes and lead glasses, but also with alkali glazes and soda glasses, but it is more common with lead glazes and lead glasses because they weather easily.
