Moisture is the enemy of the SS Great Britain and her iron hull is extremely vulnerable to corrosion. To keep the air as dry as possible the Dry Dock has been sealed by a huge water-line glass plate. The plate surrounds the ship, flooded with a shallow layer of water to give the illusion of being afloat. This also acts as an insulator, helping to save between 10% and 20% in energy bills. Beneath the plate the air is kept dry by a giant dehumidification plant (its sister plant lies inside the ship’s hull) which ensures the atmosphere around the hull is maintained at a relative humidity of 20%.
This means that the air in the Dry Dock is now as arid as that of the Arizona Desert!