FTIR is an analytical method that uses the absorption of infrared light to identify materials. In archaeology, FTIR is used for various purposes, including the analysis of amorphous organic remains, tar, the determination of clay minerals in ceramics and the identification of pigments.

Sample spectra from these materials are compared with spectra from known substances and with the Archaeological Research Laboratory's database of infrared spectra, which contains over 800 spectra from materials relevant to archaeological samples.

A IR-spectra from a sample from an archaeological context compared with spectra from the reference database to determine the best match. Image: Hans Ahlgren.

It is recommended that the sample material to be sent to us for FTIR analysis be wrapped in aluminium foil. Avoid putting the samples directly into plastic bags as this may affect the quality and reliability of the analysis. The amount of sample needed for analysis is very small, typically around 0.1–1 mg is sufficient.