A new cleaning method for historic stained glass windows

Historical stained glass has a clear tendency to form a crusted layer on its surface due to the environmental exposure. One of the most delicate aspects to be faced during the restoration of historic glass windows is the cleaning of these thick corrosion crusts.For several centuries, stained glass windows have been cleaned using damaging mechanical (scalpel) and chemical (high acidic or alkaline solutions) methods. Today's understanding of the cleaning process comprises two complementary aims: improving the readability of the glass and reducing the weathering process of the historical glass. The act of removing deposits and encrustations resulting from corrosion should not endanger the artwork itself. Mechanical methods, cleaning solutions or gel pads are now being developed. However, these methods could present further problems.In this study, we examine a new cleaning method that can be employed to remove encrustations in a quick and efficient way. Results up to now, obtained on specific stained glass windows are promising; further researches are in process for other cases. We propose an optimized solution to dissolve calcium carbonates and lead sulphates from Avila Cathedral glass windows crust. This system is tailored to control pH, temperature, conductivity and concentration of Ca2+. Continuous on-line analysis of these parameters allows us to monitor the cleaning process. In particular, the Ca2+ concentration in the cleaning solution is controlled by means of a Ca2+ ion selective analyz

High-temperature stable gold nanoparticle catalysts for application under severe conditions: the role of TiO2 nanodomains in structure and activity

Metal nanoparticles with precisely controlled size are highly attractive for heterogeneous catalysis. However, their poor thermal stability remains a major concern in their application at realistic operating conditions. This paper demonstrates the possibility of synthesizing gold nanoparticles with exceptional thermal stability. This has been achieved by using a simple conventional deposition–precipitation technique. The material employed as catalyst consists of gold supported on a TiO2-impregnated SiO2 bimodal mesoporous support. The resulting material shows gold nanoparticles with a narrow size distribution around 3.0 nm, homogeneously dispersed over the TiO2/SiO2 material. Most interestingly, the gold nanoparticles show exceptional thermal stability; calcination temperatures as high as 800 °C have been employed, and negligible changes in the gold particle size distribution are apparent. Additionally, the presence of an amorphous titanium silicate phase is partially preserved, and these factors lead to remarkable activity to catalyze a range of oxidation reactions

High-Temperature Stable Gold Nanoparticle Catalysts for Application under Severe Conditions: The Role of TiO₂ Nanodomains in Structure and Activity

Metal nanoparticles with precisely controlled size are highly attractive for heterogeneous catalysis. However, their poor thermal stability remains a major concern in their application at realistic operating conditions. This paper demonstrates the possibility of synthesizing gold nanoparticles with exceptional thermal stability. This has been achieved by using a simple conventional deposition–precipitation technique. The material employed as catalyst consists of gold supported on a TiO₂-impregnated SiO₂ bimodal mesoporous support. The resulting material shows gold nanoparticles with a narrow size distribution around 3.0 nm, homogeneously dispersed over the TiO₂/SiO₂ material. Most interestingly, the gold nanoparticles show exceptional thermal stability; calcination temperatures as high as 800 °C have been employed, and negligible changes in the gold particle size distribution are apparent. Additionally, the presence of an amorphous titanium silicate phase is partially preserved, and these factors lead to remarkable activity to catalyze a range of oxidation reactions