These materials are ‘organic’. Organic objects are most often found in damp or wet environments, as this is the environment in which they are best preserved. Damp or wet objects should not be allowed to dry out, as there is a risk of irretrievable shrinking, cracking and warping. Unworked (natural - not shaped) bone is an exception: It may be carefully washed with water and a soft bristled brush, slowly dried out, and stored dry and well ventilated.
Organic finds should be placed in a perforated polyethylene bag inside a polyethylene box, and kept cool. Exclude light, as this will discourage the growth of micro-organisms (mould can grow quickly in damp conditions.). If the object is wet rather than damp, it may be necessary to use a non-perforated polyethylene bag and add a little water to the bag. Consult a conservator as soon as possible.
These materials are ‘inorganic’. Many ceramics, glass and stone finds can be gently washed with water and a toothbrush and allow to dry naturally. However, it is of utmost importance that the nature of the material is understood before cleaning – if it is particularly fragile, has a flaking surface, is porous, has painted surface decoration/gilding, or if there is a chance that residues from use may remain, do not clean it.
Sedimentary types of stone, such as shale or slate, should never be allowed to dry out as they will shrink and crack. Treat it as organic material and keep it damp.
Metal objects should never be washed. Once air dried, they should be kept as dry as possible by placing the object, once bagged, in a sealed polyethylene box with a sachet of silica gel. Do not attempt any cleaning, as this may damage the surface, or associated evidence. Resist any temptation to rub coins and reveal detail.
Glass, when damp, can appear in a much better condition than it actually is: If there is doubt about its stability, it should be kept damp, and a conservator consulted.
If inorganic material from a waterlogged deposit appears to have organic material attached, treat it as for organic material (do not dry out), and consult a conservator.
Some finds – for instance gold and silver coins or objects, may be classed as treasure under the Treasure Act 1996. If you find objects which may be classed as treasure, they should not be cleaned. Cleaning may damage evidence and reduce any award made to the finder. A treasure item should be immediately reported to the coroner. If you are not sure if you have found treasure, speak to your local Finds Liaison Officer, who will be happy to advise you.
If in doubt consult an expert – your local museum, a conservator or your local Finds Liaison Officer will be able to advise you.