Method of carbon 14 dating
Labeling of bone samples with animal glue is an example of artificial contamination.Other contaminants that may be introduced during sample collection and packaging are biocides, conservation chemicals like polyvinyl acetate and polyethylene glycol, cigarette ash, and labels and wrappers that are made of paper.The carbon-14 atoms are always decaying, but they are being replaced by new carbon-14 atoms at a constant rate.
The specific effect of the contaminant on radiocarbon dating results depends on the type of contaminant, the degree of contamination, and the relative ages of the sample and the contaminant.
The ratio of normal carbon (carbon-12) to carbon-14 in the air and in all living things at any given time is nearly constant.
Maybe one in a trillion carbon atoms are carbon-14.
Limestone is of geological origin and would be much older than any archaeological sample; hence, inclusion of limestone during the carbon 14 dating would make the sample older than its true age.
Humic and fulvic acids are naturally present in soil where microbial degradation of plants and animals has occurred.