A NEW DATING METHOD FOR HIGH‐CALCIUM ARCHAEOLOGICAL GLASSES BASED UPON SURFACE‐WATER DIFFUSION: PRELIMINARY CALIBRATIONS AND PROCEDURES*

The first European settlers came to North America in the early 17th century using glass in the form of containers and decorative objects. Thus, glass is a horizon marker for all historic period settlements and a potential source of chronometric dates at archaeological sites belonging to the historic period in the Americas. We have developed a new absolute dating method based upon water diffusion into the surface of manufactured glasses that predicts diffusion coefficients based upon variation in glass chemical constituents. Low‐temperature (< 190°C) hydration experiments have been performed on a set of five high‐calcium (21.7–28.3%) glasses that were used to manufacture wine bottles from the 17th?19th centuries. Infrared spectroscopy and secondary ion mass spectrometry was used to model the water diffusion/alkali exchange process. The ability of the model to accurately predict archaeological ages was evaluated with artefacts recovered from ceramic‐dated contexts at Thomas Jefferson's plantation known as Monticello.