## 5 Conclusions  
This study has shown promising results regarding the use of an aqueous colloidal dispersion of nano-sized silica as a binder in chromatic reintegrations for wall paintings. Given that professional restorers must ensure the compatibility of the inpainting with the original historical paintwork, this research showed, on the one hand, that the chromatic reintegration had slightly lower gloss values than the fresco technique (except for chromium green) and could be easily distinguished from the 'historical' fresco technique. Wettability was unaffected, and both techniques (fresco and inpainting) retained their hydrophilic character. Another interesting finding was that the chromatic reintegrations had similar colour values to the raw pigment. This will enable professionals to know approximately what colour will be obtained.  
The chemical nature of pigments and the presence of impurities were determined in the compatibility with the nano-silica binder. Even though all the inorganic pigments provided promising results in terms of physical compatibility (colour, gloss, roughness,and wettability), blue silicate-based pigments showed better pigment distribution within the paint layer and outstanding adhesion to the mortar substrate compared to oxide- and sulphide-based pigments. This was likely related to the fact that silicates were more compatible with the silica-based binder.  
Finally, this study has also shown that despite its use in ancient and medieval wall paintings, the semi-organic pigment verdigris is not suitable for use in either the fresco technique or in chromatic reintegrations with NE, mainly due to the poor adhesion of the paint layer to the _intonaco_ surface. In order to understand the decay processes to which verdigris is subjected when applied to _a fresco_, more research is required into the chemical-mineralogical transformations it undergoes.  
Conceptualisation, D.J.-D., J.S.P.-A. and A.A.; methodology, D.J.-D., J.S.P.-A. and A.A.; software, D.J.-D., J.S.P.-A. and A.A.; validation, J.S.P.-A., A.A. and T.L.-M.; formal analysis, D.J.-D., J.S.P.-A. and A.A.; investigation, D.J.-D.; resources, D.J.-D., J.S.P.-A. and A.A.; data curation, D.J.-D., J.S.P.-A. and A.A.; writing--original draft preparation, D.J.-D.; writing--review and editing, J.S.P.-A., A.-A. and T.L.-M.; visualisation, J.S.P.-A. and A.A.; supervision, J.S.P.-A., A.A. and T.L.-M.; project administration, J.S.P.-A.; funding acquisition, J.S.P.-A. All authors have read and agreed to the published version of the manuscript.  
This study was funded by Research Projects PID2020-119838 RA-I00 and PID2023-146405 OBID00 (funded by MICIU/AEI/10.13039/501100011033 and FEDER, UE), and ED431F 2022/07.  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed at the corresponding author.  
[PERSON] was supported by the ED481A-2023/086 predoctoral contract through 'Programa de axudas a etapa predoutoral da Xunta de Galicia' co-financed by the European Union within the framework of the FSE+ Galicia 2021-2027 programme and partially financed by the Xunta de Galicia project _Limega sostible do patrimiono pictorio: optimizacion dos procesos de ablacion laser_ (ED431F 202/07). [PERSON] was supported by the RYC2020-028902-I project funded by MICIU/ AEI/10.13039/501100011033 and, by 'ESF Investing in your future'. [PERSON] was funded by the State Research Agency (SRA) and the Spanish Ministry of Innovation and Science, as part of the projects PID2020-119838 RA-100 (2021-2024) and PID2023-146405 OB-100 (2024-2027), within the Junta de Andalucia Research Group RNM179. [PERSON] was funded by Grant C-HUM-109-UGR23 funded by Consejeria de Universidad, Investigacion e Innovacion and by ERDF Andalusia Program 2021-2027 and pre-competitive project PP2024.PP-02 of the University of Granada.  
The authors declare no conflicts of interest.