# A Survey of Electromagnetic Techniques Applied to Cultural Heritage Conservation
## 3 EM Techniques for CH Restoration
### EM Techniques for Decontamination of CH
#### 3.1.2 Microwave (MW) Heating and Radiofrequency (RF) for Decontamination of CH  
Although MW heating and RF treatments are not that common, we will spend a few words on them, for the sake of completeness. Microwave heating has been widely used for industrial and medical applications, but because of the peculiarity of CH artifacts in terms of the variety of materials within the same object and irregular shapes, this technique may lead to overheated areas, while others remain scarcely irradiated [89].  
For these reasons, most applications may be found for stone treatments, particularly building walls, which means artifacts mainly made of one material and with a relatively regular shape compared to the majority of CH objects [38; 39; 40]. [PERSON] et al. [39] used a 2.45 GHz microwave generator to eradicate a fungal colony isolated from cultural stone artifact. The temperature rate was increased depending on the material characteristic and power level of microwave radiation. Experiments show an evident influence of microwave heating on three different fungal colonies; in all cases, an exposure time of more than 9 min at 55 \({}^{\circ}\)C was enough to inhibit growth or kill the colony. Nevertheless, there are different cases in which this technique has been applied to other types of CH manufacture for decontamination purposes. [PERSON] et al. conducted a study on the use of localized MW heating treatment for biodeterioration control not only on stone, but also on wooden objects [93].  
Wood artifacts are among the most treated by means of the MW heating method [41; 42; 43], especially for the eradication of woodworms in all metamorphic stages (eggs, larvae, and pupae), including in painted boards [34]. [PERSON] et al. [42] assessed a procedure to eradicate woodworm larvae from wild pine. The aim was to find the right combination of time and power to eradicate the pest, preserving the integrity of the wood. According to the authors, the right combination in their experiment was a microwave-power of 1 kW for 20 s.  
Regarding MF, it has been applied to remove biofilms from ceramic surfaces. The studies were mainly conducted by [PERSON] et al. from the University of Federico II, Naples. Biofilms not only produce aesthetic alterations, but also induce physical damage to the surfaces on which they grow. Biodeteriogens identified by [PERSON] et al. on terracotta pots fall into three main types [45]:  
* Eubacteria (five different species isolated in their research);
* Cyanobacteria (10 different species isolated in their research);* Green algae (13 different species isolated in their research).  
Shards of broken spots were inoculated with biofilm samples of the three different types of biodeteriogens, and exposed to RF treatments: two hours of exposure every other day for a week. The average reduction was more 81% for all three species. The authors also report that the RF power level applied (although not specified) did not produce any significant temperature increases in the treated surfaces.  
Other research has been conducted by [PERSON] et al. on the use of EMWs in the range of RF for biofilm removal [46; 47], but these are still niche studies. Figure 2 shows a confocal laser scanning image of biofilm on a Candoglia marble, even after chemical cleaning combined with a mechanical brushing treatment [80].