It is black because cuttlefish juice contains black particles invisible to the naked eye-actually it is a viscous suspension.
The particle are spherical,
The diameter is generally120-180 nm.
Particles have two-layer structure: a high-density inner core and a low-density outer shell. The inner core is called squid ink melanin. The chemical composition of squid ink is a complex of melanin and proteoglycan. Melanin is a polymer of indoquinone (indirubin), which is bound to or not bound to protein. Writing with cuttlefish juice looked black and shiny, clear and beautiful at that time; But after a long time, it will oxidize, the ink color will all fade away, and the handwriting will naturally disappear.
In ancient times, it was based on
This characteristic of cuttlefish juice
I made a bad idea: first, I borrowed money, things, food, etc. from others, and then I solemnly set up an iou with cuttlefish juice, but it was delayed for a long time. At the beginning, the words and ink were bright, but after half a year, they were indifferent and traceless; If the creditor urges him to pay back, when the borrower asks for the IOU, he will suddenly find that the IOU is a blank piece of paper-there is no handwriting and no evidence; The borrower refused to pay back the debt. Later, people knew that it was a ghost made by cuttlefish ink, and they hated it with their teeth gnashing, calling cuttlefish a thief who helped the bad guys to default, so they called it squid.
The song dynasty was careful in "
The origin of the & of the squid is described in detail in the sequel to Gui Xin's Miscellaneous Knowledge: ldqu