When artefacts are discovered, they are often broken, decayed and in a very fragile state.  Careless handling can result in their destruction and the loss of the information about the past which they represent.  Even artefacts which appear to be more robust or complete can be subject to less obvious processes of decay; objects do not always rot on the outside first.  Ground conditions affect to a great extent the sort of materials which survive.  Permanently waterlogged or anaerobic (without oxygen)  conditions are very good for the preservation of organic matter, such as wood, seeds and leather.  This is because the micro-organisms which cause decay in organic matter need air to survive.  Exposure to air and light can be very destructive and can accelerate the process of decay.

 

The oxidation of surface deposits can quickly dull and erase colours or traces of ancient writing.  Copper and bronze, which would have been a dark reddish gold when in use, is commonly oxidised to a powdery green colour when discovered in archaeological deposits.  Iron turns a rusty and flaky red.  Where the oxidisation of the object is so deep that there is little of the original left, the object can easily disintegrate.  A range of techniques are used to conserve objects: in the case of organics such as wood, the water moisture within the internal cellular structure which prevented the wood from drying up and collapsing, is slowly replaced by stabilising synthetic chemicals.  

 

When discovered, an object may already have been, or may still need to be, removed from the ground conditions in which it has lain since it was deposited many centuries ago.  Lifting an artefact can destabilise it and cause cracking, so fragile objects are often lifted in a block of soil to help to support them.  Contamination by human touch or the wrong chemicals can spoil the potential for further scientific analysis.  Conservators are trained to know the dangers to ancient artefacts, and how to avoid any unnecessary damage.  On-site conservation involves the careful intact removal of the object; off-site conservation involves the analysis and preservation of the object so that its full potential to inform us about the past can be realised, and so it may be kept permanently in a museum.