The sampling strategy is an integral element of the excavation research design, although sampling is not carried out on all sites. A range of artefacts, ecofacts and deposits are retrieved by hand and by collecting and sieving the contents of features. Not all artefacts and ecofacts will be retained for analysis and the sampling strategy will define the percentage of features to be sampled. The potential for further analysis of sampled material is either assessed on an ongoing basis or at the end of the excavation phase and is referred to as post-excavation assessment.
Soil samples may be taken for analysis of chemicals, pollen or other materials, while objects may be sampled for radiocarbon dating, isotopic analysis, DNA analysis, etc. Samples may be taken from different features or from construction materials including bricks or wood.
In some countries, sieving is more common on research based excavations where more time is available. Flotation is a technique that works by passing excavated spoil onto the surface of water and separating finds that float from the spoil which sinks. The ‘light’ residue which floats is primarily of interest for archaeobotanical and charcoal studies, whereas the ‘heavy’ residue provides material for a wide range of specialists. Both sieving and flotation are used to maximize the recovery of small artefacts and ecofacts.