Black and yellow dating
Unfortunately there are no affordable direct methods for dating pigments, except in some cases as we will see later.
Generally, for example, we can’t establish when a vermilion stroke was brushed onto a painting, but we can date most of the materials that the pigments are painted on.
When collecting samples for thermoluminescence dating, several samples from different vessels should be taken, not smaller than 1 gram.
Samples should not be exposed to heat and powdery examples should not be exposed to bright light.
Electron trapping Energy absorbed from ionizing radiation frees electrons to move through the crystal lattice, where some are trapped at imperfections.
Later heating releases the trapped electrons, producing light whose intensity is proportional to the amount of radiation absorbed.
A sample of the earth also needs to be collected so environmental radiation can be tested.
Eventually, we will follow this formula to found out how many years old the sample is: Age (year) = accumulated dose / dose rate per year Thermoluminescence dating can be performed only in a specialized laboratory which will have a chemical section for the treatment of the samples with reagents and a radiation hazard restricted area.
Natural radioactivity causes latent thermoluminescence to build up so the older an object is, the more light is produced.
Therefore, thermoluminescence dating is actually determining the last time a crystal was heated and electrons were released.
Indeed, the figure shows an automatic instrumentation which allows measurement of thermoluminescence light from samples and also the determination of the dose rate per year.
This last procedure involves the use of a radioactive source, though very weak.