The Condition of Contemporary Murals in Sun-Exposed Urban Environments: A Model Study Based on Spray-Painted Mock-Ups and Simulated Light Ageing

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors The article is well-written and based on a thorough literature search. The investigations carried out and the results of the research open up new insights that the authors themselves want to explore further in a second phase. Additional files have also been presented to help the researcher understand the research.

In my opinion, no further editing is necessary.

 

Reviewer 2 Report

Comments and Suggestions for Authors

The central focus of this research is to explore the physicochemical stability of spray-paints used in modern murals when exposed to simulated solar light. The study meticulously examines how different components within these paints degrade over time due to photochemical ageing. This work is vital for preserving urban murals, which hold significant cultural value today, and this topic is not enough discussed in litterature.

What makes this research stand out is its innovative approach to studying spray-paint degradation. The use of a broad range of advanced analytical techniques—such as stereomicroscopy, SEM, AFM, contact angle measurement, colorimetry, glossimetry, DSC, UV-Vis spectroscopy, ATR-FTIR, and Py-GC/MS—provides a comprehensive understanding of the effects of solar irradiation on these materials. The inclusion of various brands and colors of spray-paints, representative of those used by Greek street artists, adds practical relevance and depth to the findings.

The paper addresses a crucial gap in our knowledge about the long-term behavior of outdoor spray-paints and the specific degradation mechanisms caused by solar light exposure. This research contributes significantly to the field by offering new insights into the degradation processes of these paints, particularly highlighting the different stability levels of various binders and pigments, and the impact of additives and fillers.

Compared to other (few) studies, this work adds substantial value by systematically comparing the responses of different spray-paint types to accelerated solar light ageing. It sheds light on unique photoageing mechanisms in white spray-paints involving titanium dioxide (that enhance photocatalysis), an area that clearly warrants further investigation and opens new research possibilities.

The tables and figures are effectively designed and clearly illustrate the narrative, while the quality of the data is commendable. Including more replicates and controls could further strengthen the results. The references are appropriate and relevant, but expanding the number of cited works would help contextualize the findings within the broader field, providing a richer comparative framework.

The conclusions drawn are well-supported by the presented evidence and thorough analysis. However, to enhance the robustness of the findings, it might be beneficial to standardize initial conditions, such as film thickness and surface texture, more rigorously. Incorporating additional environmental factors like humidity and temperature variations could also provide a more comprehensive understanding of paint degradation.

Overall, this manuscript is an excellent and valuable contribution to the field of heritage science, particularly in the conservation of contemporary urban murals. The authors have produced a detailed, well-supported study that advances our understanding of spray-paint degradation under solar exposure. While some minor methodological enhancements could be considered, the manuscript as it stands is a highly commendable piece of research and I suggest acceptance as it is.