Rafter carbon dating
Often, submitted samples are divided and one portion retained as a reference in case the original sample is lost, or a further date required.
Sometimes, submitters perform basic pretreatments, usually involving a wash in distilled water and the removal of root material.
This should be reported in the submission forms accompanying samples sent to the laboratory.
Contamination may be artificially or naturally caused.
Sometimes, a precise date is not needed and pretreatment methods designed to reduce errors will not be necessary.
Many commercial laboratories have different charges for dating depending on the precision (and speed) that is required.
The most common source of contamination by modern carbon is caused by rootlet intrusion.
The submitter should also describe the relationship between the material and the geological, or archaeological context to be dated.
Artificial contamination may be blamed on human negligence during the collection and processing of samples.
Contaminants often include ash from tobacco, hair and fibres, paper from packing material and oil or grease (Hogg, 19).
If pretreatments were able to be uniformly implemented, there would have to be a uniform and predictable array of post-depositional characteristics between all samples. Each sample submitted for dating has its own specific depositional history.
The variety in environment and post-depositional features is reflected in the variety and complexity of pretreatment procedures and the variety of different types of dateable material (see above).