If the clay is older than the time of firing, the carbonate age will also be older than the time of firing.
If the CO2 is available from the firing fuel, the age of the shell will reflect the age of the fuel.
There are many people who can't tell when a piece of pottery was made.
I appraised a mascara jar that was so old it dated back to the lifetime of the ancient Egyptian queen, Cleopatra, circa 50 BC.
The following are listed in order of Beta Analytic’s preference:1- Date the charred food residue found on the interior surfaces The lab prefers to date the burned food residue extracted from the interior surfaces of a sherd as this offers the best chance of a date that will be representative of the last time of usage.
In general the burned food residue has to be a patina that can be removed in small bits or chunks rather than a sooty powder.
Most pottery that is found today does not date back so far. While I can identify an ancient piece and tell you its value, I can help you--via my tips--show you how to spot a valuable ceramic and to identify pottery marks from more recent history.
Therefore, the accuracy of the radiocarbon date depends upon where the wood came from within the tree. Read about sample material return How much does carbon dating cost?
NOTE – If you are not sure what might be dated for your pottery sherd, please contact us prior to sending your sample to the lab.
With radiocarbon dating, the greatest bias is always in the more recent direction as modern carbon adds both carbon by weight and radioactive 14C by content whereas older contamination (or very old clay) has less of an impact unless there has not been any secondary contamination by younger carbon.
If the temperature exceeds 600°C, the carbonate can dissociate, releasing its carbon as carbon dioxide (CO2).
Upon cooling, any available CO2 will reform the carbonate.