When you have something precious, you want to keep it forever. In the case of historical documents that serve as invaluable markers of your nation’s culture, you want to ensure their availability to researchers of the far distant future.
That’s the idea behind the Barbarastollen underground archive, Germany’s central repository for images and documents. Opened in 1975, the high-security facility near Freiburg makes its home in a converted mine shaft, sheltered from any foreseeable disaster by over 400 meters of solid rock.
Documents archived in this treasure chamber – over 900 million in all – include such gems as Otto the Great’s coronation certificate from the year 936, manuscripts of Goethe and Schiller, the Treaty of the Peace of Westphalia and the original building plans for Cologne Cathedral. To maximize the lifespan of their archive, designers chose the most long-lasting, dependable material available: stainless steel.
The documents at Barbarastollen are stored on microfilm, which continues to be the archivists’ medium of choice thanks to its immunity to technological change. A light and a magnifying glass are all it takes for document retrieval. Just as important, today’s microfilm uses a highly stable polyester base that gives it a life expectancy of 500 years or more. But, critically, that expectancy can be reached only under the proper storage conditions. To meet those conditions, the reels of microfilm are sealed in 78-centimeter tall stainless steel containers, each weighing 122 kilograms.
Made of a long-trusted, austenitic grade equivalent to Outokumpu’s Core 304/4301, these airtight containers are preconditioned to create a dust- and pollutant-free micro-climate, with 35% relative humidity and a temperature of 10 degrees Celsius. The walls of the archive are lined with 1,450 numbered stainless steel barrels, each containing some 24,000 photographs, all of which will allow future generations to travel back in time through Germany’s cultural history.
Core 304/4301 is an old favorite among stainless steel grades. This standard, austenitic variety contains 18% chromium and 8% nickel, a balance that lends it a good level of corrosion resistance as well as makes it easily formable and weldable. This reliable, all-purpose material is used in everything from machine parts to plumbing to consumer goods and, thanks to its longevity, is an ideal choice for long-term projects like the Barbarastollen underground archive.