Decay prevention in waterlogged archaeological wood using gamma irradiation

Gamma irradiation is evaluated as a novel decay prevention treatment for waterlogged archaeological wood. A dose of 15 kGy was found to be sufficient to inactivate a large number of wood biodeteriogens, including fungi, bacteria and invertebrates, at various stages of development. For timbers excavated from polluted sites, a dose of 25 kGy is suggested to inactivate human pathogens. The dose spread required for such treatments are 1.33:1 and 1.2:1, respectively, in timbers up to 150 mm thickness and density not exceeding 1590 kg/m3. No adverse effects on the physical properties of slightly or heavily degraded waterlogged archaeological wood were detected at doses of up to 100 kGy. This is the maximum recommended single or cumulative lifetime dose for any timber. Gamma irradiation offers far greater efficacy over currently used decay prevention treatments and, a step-wise procedure for evaluating timbers for treatment and dosimetry is presented.