Preservation of the Evidence A Multi-discipline Task

Whenever possible, objects should be lifted in a rigid container (not in a bag) and packed with a representative sample of the surrounding matrix to limit movement and damage during recovery. A supply of numbered plastic boxes with attached lids should, like the sandbags, be stored close to the excavation. If surface conditions are severe, the containers, suitably numbered and recorded, can be stored on the bottom until calmer conditions occur. 

In other parts of the world, a synthetic grass mat has been used to collect current-borne sediments enabling a protective mat of sand to accumulate. In Boa Vista, Cape Verde Islands the natural seabed is composed of water-worn pebbles of volcanic rock. These are easy to handle underwater and a layer of 100 mm pebbles overlain with some well-chosen boulders protects the site from marine and human interference. The insertion of a short tail of orange cord serves as buried marker. It is discrete, moving gently in the current, and to the casual intruder is much like other marine growth and debris. 

The need for on-site conservators and recorders is obvious. Some details like paint marks on wood or stone are often fugitive and fight labile, as were the markings on the parts of a seaman s chest from the Mary Rose indicating how they fitted together. Obviously it was a flat-pack kit purchased for later assembly. Within 20 minutes the marks had been photographed, but they were beginning to fade and there is no trace of them today. 

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