Want to make a book last for over 2000 years? Check out a unique ancient technology of parchment-making to better preserve precious historical documents. First discovered in 1947 by Bedouin shepherds looking for a lost sheep, placed in jars and hidden in 11 caves, the ancient Hebrew texts known as the Dead Sea Scrolls are some of the most well-preserved ancient written materials ever found. A study by researchers at MIT has observed that the Scroll parchments were made from animal skins soaked in a lime solution, scraped them clean, and then stretched tight in a frame to dry. When dried, the surface was further prepared by rubbing with salts, as was apparently the case with the Scroll. The scientists found some elements like sulphur, sodium, and calcium in different proportions, spread across the surface of the parchment, at completely unexpectedly high concentrations that protected the writings.