Preservation
Due to the instability of Han purple, it shows significant signs of weathering on archaeologically excavated artifacts. The copper(I) oxide formed in the decomposition of Han purple (see section on color) remains stable, but Han purple continues to deteriorate and so its purple color increases with time.
Han purple fades in acid, so colorless particles found in pigments containing Han blue and Han purple may be particles which were originally purple but which faded in acidic conditions in burial. In addition, Han blue has fungicidal properties and so preserves better. Han purple reacts with oxalic acid to form BaCu(C2O4)2. The light blue color of this salt may explain the light blue color of some of the Terracotta Warriors' trousers - the color resulting from the presence of oxalate-excreting lichens.
Read more about this topic: Han Purple And Han Blue
Famous quotes containing the word preservation:
“It is my hope to be able to prove that television is the greatest step forward we have yet made in the preservation of humanity. It will make of this Earth the paradise we have all envisioned, but have never seen.”
—Joseph O’Donnell. Clifford Sanforth. Professor James Houghland, Murder by Television, just before he demonstrates his new television device (1935)
“The preservation of health is a duty. Few seem conscious that there is such a thing as physical morality.”
—Herbert Spencer (1820–1903)
“I do seriously believe that if we can measure among the States the benefits resulting from the preservation of the Union, the rebellious States have the larger share. It destroyed an institution that was their destruction. It opened the way for a commercial life that, if they will only embrace it and face the light, means to them a development that shall rival the best attainments of the greatest of our States.”
—Benjamin Harrison (1833–1901)