Each time the sample is irradiated and then heated, the pre-dose peak increases. The first increase is due to the natural dose which the piece has absorbed over its life-time.
The sample is then given a laboratory irradiation and a second increase is measured.
The ceramics come from two recently excavated sites at “Hellenikon” and “Ligourio” in Argolid, Peloponnese, Greece.
Two forms of luminescence dating are used by archaeologists to date events in the past: thermoluminescence (TL) or thermally stimulated luminescence (TSL), which measures energy emitted after an object has been exposed to temperatures between 400 and 500°C; and optically stimulated luminescence (OSL), which measures energy emitted after an object has been exposed to daylight.
To put it simply, certain minerals (quartz, feldspar, and calcite), store energy from the sun at a known rate.
Any remaining powder is dried and used for radioactivity measurements to complete the dating calculation. When the glue is dry, they are cut into slices 1/4mm thick with a fine diamond blade. Each slice is soaked in acetone after cutting to remove the glue. The remaining core is crushed and used for radioactive analysis to complete the dating calculation.
We have 3 fully automated, computer operated Riso Minisys TL readers for measuring the TL.
For the modern vase the archaeological signal is barely above background and well below the TL signal from the applied laboratory dose.