# A Survey of Electromagnetic Techniques Applied to Cultural Heritage Conservation
## 3 EM Techniques for CH Restoration
### EM Techniques for Decontamination of CH
#### 3.1.1 Application of Gamma and X-Ray for Decontamination of CH
The same results have been obtained by [PERSON] et al. [64], but considering a wider range of doses, 1-50 kGy. Although side effects on transparent materials are confirmed, [PERSON] et al. [91] report that the Color Centers Activation starts for doses above 1 kGy which, as previously recalled, is the maximum value of D\({}_{10}\) for most fungi and molds. Gamma irradiation has also been used for disinfection on an \"oil painting experimental model\" of 1995 by Romanian artist, [PERSON], [32]. The painting has been irradiated at an average dose of 33 kGy, three times higher than the dose of 10 kGy generally effective for decontamination, and at an average dose rate of 3.1 kGy/h. The painting's layer structure and color changes have been monitored by Fourier Transform Infrared Spectroscopy (FTIR) and Fourier Transform Raman (FT-Raman) spectroscopy. [PERSON] et al. [32] report that, despite the high irradiation dose, insignificant spectral changes were observed in the oil painting after irradiation. Beyond these examples, the use of ionizing radiation for decontamination is mostly related to the treatment of organic artifacts made of paper, parchment, wood, and textiles, and of a particularly fascinating type of CH object, mummies. The eyes of the world are focused on them because of their imaginary power, and because they are made of different highly perishing organic materials, from human tissues and bones to textile materials; this fact represents a great challenge from a technical point of view as, according to what stated in the introduction of Section 3, the irradiation dose needed for decontamination is inversely proportional to the complexity of the organic molecule to be irradiated. For mummies' disinfection, gamma radiation turned out to be the best choice because of its efficiency and jet safety, provided that the right dose rate is applied. Even for one of the most important cases of CH object decontamination, the mummy of [PERSON], it is not easy to find information apart from those provided by IAEA [14; 33]. The image reported in the upper part of Figure 1 is a photo from 1912. The mummy of [PERSON] not only has incredible historical value, but its treatment is also incredibly challenging from a technical point of view, since it is made of different organic materials:  
* Hair;
* Skin;
* Teeth;
* Textiles. The species of fungi present on the mummy at the time of disinfection were more than 60 (as reported by IAEA [14]); hence, the minimum dose approach was impracticable [33]. Moreover, due to the extremely irregular shape and density of the mummy, a calculus model has been necessary to design the gamma ray source in a way that irradiation parameter of a minimum dose rate of 18 kGy was guaranteed to all parts of the mummy. The irradiation time was 12 h and 40 min, with a rotation of the mummy at half of this period. Notice that the mummy, as well as the sarcophagus, had been previously sealed in a plastic envelope in order to preserve it in a sterilized environment during manipulation. The result was a real success, with the mummy still in very good condition nowadays. A case, similar in certain aspects to that of mummies, because it deals with organic material, is the case of the frozen baby mammoth. The selected dose was 20 kGy of gamma radiation with a maximum level of 40 kGy; hence, much higher than the maximum dose of 10 kGy usually reached in CH treatments. These levels of irradiation caused lesions to the DNA, although the integrity of the protein structure of the animal was preserved. Even in this case, the only information we could find are those reported by the IAEA [14]. In [10], the importance of radiation treatment is outlined when large collections are affected by serious biological attacks; this is usually the case in libraries and paper or textile collections. An example of mold disinfection through gamma radiation in the case of large collections is the disinfection of the Peace Palace Library in the Netherlands.