**3. Conclusions**

**3. Conclusions**  This work provided detailed information on the material composition of the color palette, by means of a combined imaging and spectroscopy method. HSI analysis has proven to be a powerful tool, and it allowed us to describe details on the distribution of the pigments, as well as a description on the manufacture of the painting. It also provided information on the presence of later repairs (consistent with UV imaging analysis), as well as insights on the existence of a previous painting (as was demonstrated by radiography This work provided detailed information on the material composition of the color palette, by means of a combined imaging and spectroscopy method. HSI analysis has proven to be a powerful tool, and it allowed us to describe details on the distribution of the pigments, as well as a description on the manufacture of the painting. It also provided information on the presence of later repairs (consistent with UV imaging analysis), as well as insights on the existence of a previous painting (as was demonstrated by radiography of the painting).

of the painting). In this artwork, the selection of materials by the artist considered the importance of the represented objects. Golden regions are present with different shades and finishes, and a gold alloy was used for the trimming, stellarium, crown, and frame. Fe was used for brown layers in the shadows. Tin lead yellow is present in jewelry highlights, orpiment in the earrings, and in radiance of the Virgin Mary. Blue tones characterization indicates the use of only two pigments: azurite for the Virgin's mantle and the clothing of the right angel; and indigo for the Holy Spirit region. A single green pigment was found in the painting, located in the representation of emeralds, and the stems and leaves in the palm In this artwork, the selection of materials by the artist considered the importance of the represented objects. Golden regions are present with different shades and finishes, and a gold alloy was used for the trimming, stellarium, crown, and frame. Fe was used for brown layers in the shadows. Tin lead yellow is present in jewelry highlights, orpiment in the earrings, and in radiance of the Virgin Mary. Blue tones characterization indicates the use of only two pigments: azurite for the Virgin's mantle and the clothing of the right angel; and indigo for the Holy Spirit region. A single green pigment was found in the painting, located in the representation of emeralds, and the stems and leaves in the palm and the lily in the lower area, which has been identified as copper resinate. Brown areas exhibit the presence of Fe, which is related with the use of burnt earth, used in the hair and pupils of Mary and the angels. Flesh tones of Mary and the angels contain a mixture of white lead, vermilion, azurite, and calcine natural iron oxide.

Results suggest the knowledge and experience of an oil-on-wood painter who possibly still conformed to the conditions of the ordinances and traditions established in the prior two centuries of colonial establishments. For the wood panel, its cut and construction are due to a process of specialized knowledge of carpentry work. However, it would be worthwhile to carry out studies on the cellular structure of the wood, the ring count to identify the selected genus, its possible extraction region, and when the tree was cut, in order to specify the work production system, in terms of the time and use of material resources.

Regarding the color palette, the system of selection and application of materials possibly considered qualities of stability, accessibility, and cost, which makes us think about the knowledge and versatility on the part of the architect to work with the different materials available.

It is also necessary to mention that the non-invasive studies by imaging techniques complemented with FORS and XRF spectroscopic techniques, although they offer high sensitivity and precision, had limitations in interpreting the areas of analysis, due to the complex layer superposition in the painting. The continuity of this study is suggested through the application of invasive techniques by means of a strategic selection of samples, and their eventual analysis by optical and electron microscopy to identify the sequence of their application and distribution, as well as the underlying pictorial campaign.

**Author Contributions:** M.P.: Writing–original draft, Methodology, Software, Formal analysis, Investigation. N.C.: Writing-original draft, Project administration, Methodology, Formal analysis, Investigation. J.L.R.-S.: National Laboratory Manager, Funding acquisition, Project administration, Investigation, Writing-review and editing. A.M.: Writing-review and editing, Formal analysis, Investigation. O.G.d.L.: Writing-review and editing, Methodology, Visualization, Investigation. Authors M.P. and N.C. contributed equally to this work and they both should be considered as FIRST AUTHOR. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by CONACYT, grants numbers LN315853, LN299076, LN 314846, CB239609 and by DGAPA-PAPIIT grants numbers IN108521 and IT101219.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** We express our gratitude to the following individuals and *institutions*: María del Perpetuo Socorro Villarreal Escárrega, *Asuntos Jurídicos INAH*; Maria del Carmen Castro, Liliana Giorguli, Irlanda Fragoso, Emmanuel Lara, María Eugenia Marín Benito, Cristina Noguera *CNCPC-INAH*; Antonio Huitrón Santoyo, Josué Alcántara, *Centro INAH Estado de México*; Armando Rosas, *Museo Ex Convento San Agustín Acolman.* We acknowledge the technical support of E. Casanova a I. Rangel. M. Pérez and N. Cano acknowledge the support of PNPC scholarship granted by CONACYT.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. *Heritage* **2021**, *4* FOR PEER REVIEW 19

### **Appendix A Appendix A**

A general description of the acquisition regions and points for the different analysis techniques are presented here. A general description of the acquisition regions and points for the different analysis techniques are presented here.

**Figure A1.** Hyperspectral analysis locations and dimensions. A total of six regions were studied in this research work by HSI technique. **Figure A1.** Hyperspectral analysis locations and dimensions. A total of six regions were studied in this research work by HSI technique.

*Heritage* **2021**, *4* FOR PEER REVIEW 20

**Figure A2.** General diagram. Superposition of visible image and radiography image of *Purísima Concepción*, indicating the acquisition points for XRF (nn.XRF) and FORS (nn.FORS) spectroscopic techniques. Underlying features are highlighted with colors to facilitate the reading of the image. **Figure A2.** General diagram. Superposition of visible image and radiography image of *Purísima Concepción*, indicating the acquisition points for XRF (nn.XRF) and FORS (nn.FORS) spectroscopic techniques. Underlying features are highlighted with colors to facilitate the reading of the image.
