h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

...Was the story of what the staff of National Archives are doing to protect the Constitution, the Declaration of Independence and the Bill of Rights.

It was interesting to compare the physical state of these compared to the much older Magna Carta. The techniques used to create them are nearly identical. Both use the same type of ink on parchment. The ink is very stable, but the parchment isn't (being skin).

The text of the Magna Carta is as legible today as it was centuries ago. Parts of the Declaration have completely faded away.

The difference is the Magna Carta is stored out of the light. The Charters of Freedom, as they are known, are on permanent display to the public and while stored in the best methods currently available, are nevertheless exposed to light which has degraded the text.


http://www.pbs.org/wgbh/nova/charters/about.html

Yeah, that's interesting. Lots of copies of the Declaration, Constitution and Bill of Rights were made. I don't believe all of them are displayed, incidentally.

What is it about light that hurts parchment I wonder?

Light degrades all manner of things, especially the ultraviolet portion of the spectrum. The glass blocks most of the UV, but even visible light is detrimental over time. It is radiation after all. Parchment is organic material and composed mostly of long chain-like molecules called polymers. Light breaks up these chains (depolymerisation).

http://www.kb.nl/cons/leather/chapter3-en.html

Also, "In photochemistry light acts as a catalyst in activating oxygen. Oxygen subsequently acts as an oxidant for the conversion of sulphur dioxide into sulphuric acid. The result is a breakdown of the links between tannin and leather fibre, followed by rapid depolymerisation of the leather and the chemical decay of the tannins."

Excellent article, very highly readable and enjoyable.