Why Doesn’t the Declaration of Independence Disintegrate?

Every Fourth of July, Americans celebrate the signing of the Declaration of Independence — the document announcing the birth of a new, monarch-free nation. But while its ideas have proven durable, the document itself is surprisingly fragile.

The declaration wasn’t written on modern paper but rather on parchment, a material that can crack, fade, warp, and deteriorate over time. For a quarter millenium, the document has faced threats from light, humidity, air, and even the ink used to write it.

As the United States marks its semiquincentennial (aka its 250th birthday), preserving the Declaration of Independence means protecting it from one of its biggest foes: the passage of time itself.

How to Keep 1776 Alive

The Declaration of Independence doesn’t just face threats from theft, fire, or even the occasional overenthusiastic tourist. As with many treasured antique documents, whether old family letters or historical manuscripts, one of its biggest enemies is chemistry.

Like all organic materials, parchment — which is made from animal skin — changes over time. The parchment contains collagen, a protein that can become brittle in dry conditions. The ink used to write and sign the document doesn’t help, either. 

The founders used iron gall ink, which is dark and durable but also acidic enough to break down cellulose chains in the parchment. Plus, it can increase oxidation — another threat to the material, as oxygen can also chemically react with both the parchment and the ink, contributing to their deterioration. 

Changes in humidity can also cause the ink to flake away from the parchment beneath it. Even tiny amounts of air and moisture can accelerate the disintegration of the document. In extreme cases, excessive moisture can break down its collagen fibers into gelatin. (Americans love Jell-O, but not in its founding charters.)

Light presents yet another danger. Ultraviolet radiation can fade inks and damage organic materials. Because of these threats, conservators have created a miniature habitat to protect the Declaration of Independence, designed specifically for its needs. Today, the declaration is displayed inside a custom-built encasement at the National Archives in Washington, D.C.

The frame is made from single pieces of aluminum and titanium (any cracks could let in air) and sealed tightly. Instead of ordinary air, the case is filled with argon, an inert gas that doesn’t chemically react with the parchment. Specially designed glass inside the frame protects the precious parchment from harmful light. The parchment itself never touches the glass, reducing the risk that ink could lift away from the parchment’s surface.

The environment inside the case is carefully controlled. Relative humidity is maintained at about 40%, which helps keep the parchment stable. The document also rests on materials that help regulate moisture.

Sensors built into the encasement continuously monitor conditions inside. Light beams, mirrors, and instruments detect changes in humidity and even subtle shifts in the composition of the gas surrounding the document. 

These precautions may sound extreme, but they reflect a simple reality: The declaration, like the rest of us, is aging. No preservation system can stop time entirely. The goal is simply to slow the process as much as possible.

The result is something like a life-support system for a document — a carefully engineered bubble designed to protect a single sheet of parchment from the outside world. Thanks to this combination of science and conservation, the historic words written in 1776 will hopefully remain visible — and relevant — for many Independence Days to come.