Urushigami Monjo (漆紙文書)
Urushigami Monjo refers to the ancient documents that remained without corruption and were made by using the disposal documents as the paper lid of the container that had lacquer inside and permeating lacquer into the paper. The example of the first nationwide was the one found in Taga-jo Castle (Tagajo City, Miyagi Prefecture) in 1973.
The lacquer liquid used for lacquering has a property to be harden when it is exposed to air for a long time, so when you preserve it, it should be covered with the paper stick to the surface without exposing lacquer liquid to air.
In ancient times, paper was of particular value, so the disposal documents was re-used as the lid for the lacquer liquid. As a result, the lacquer was permeated into the paper and made it avoid corruption in the soil. Therefore, only the shape of the liquid surface remained and it was mostly rounded shape.
It is hard to decode to the naked eye, so an infrared camera is used for decoding.
Urushigami Monjo is the segment of the disposal documents, but it is valuable material among the primary archives of the ancient times remained, together with mokkan (a narrow strip of wood on which an official message is written), ink writing earthenware, and Shoso-in monjo (documents of Shoso-in).
Other than letters, official documents of the time, such as ancient family registration system, calendar, keicho (the yearly tax registers), and Shibo-cho (record of the dead), were found.