Is carbon dating affected by water?

THE hard-water effect is a recognized source of error in radiocarbon dating. It causes ages to be over-assessed and arises when the material to be dated, such as mollusc shell or plant, synthesizes its skeleton under water and so uses bicarbonate derived in part from old, inert sources.

What is the limit of carbon dating?

Since there are practical limits to the age range of the method, most samples must be younger than 50,000 years and older than 100 years. Most samples require chemical pre-treatment to ensure their purity or to recover particular components of the material.