The most fragile items, Mertens explains, and the hardest ones to conserve, are made of silk. “Linen for instance, is very strong,” he notes. “It keeps in shape forever. The mummies in ancient Egypt were wrapped in linen. We actually have some fabrics from ancient Egypt, and the ones in linen you can’t tell the difference if they’re 5,000 years old or 200 years.” Above: A box full of cotton children’s bonnets dating back to the late 1800s.