Historic K-rich silicate glass surface alteration: Behaviour of high-silica content matrices

Abstract

Several K-Ca-Si glass compositions typical of Central-European glassworks are susceptible to damage beyond recall, even in mild museum conservative conditions. In order to provide a comprehensive picture of the deterioration process, replica samples were produced and exposed to four different museum-like environments. The corrosion experiment was followed by the use of ToF-SIMS, µ-Raman and µ-FTIR, performing a systematic compositional and structural study for the early stages (one year) of surface alteration. This work demonstrates the dominant role of Pb 2+ and Ca 2+ content for the inferable existence of connected conduction pathways, with strong implications on the surface's hydration, alkalidiffusion and hydrolysis.

Mixed reactions: Glass durability and the mixed‐alkali effect

“…52 Therefore, it is in this way that the resistance of the presently studied MA to moisture attack is in accordance with the MMCE model which considers the above described "cooperativity blockage" of alkali-pathways. This is somewhat also in accordance with the suggestion made for the K-rich glass types aged under the same conditions, that there was a contribution of the cations for the proneness of formation (before or during reaction with moisture) of connected conduction pathways 32 through which the mobile alkalis, and possibly also the hydrogenated species, travel. 46 Moreover, the proposed explanation for the MA resistance under the MMCE model also seems to fit within the recently proposed porosity model which considers the influence of | 7285…”

“…The very low degree of alteration observed in the studied MA glass surfaces needs to be discussed in the light of the recently presented alteration behavior of Na‐ and Na–Ca‐ rich, as well as K‐rich glasses produced and aged under the exact same environmental conditions . Although the glass durability and alteration behavior are a result of a complex system, from the comparison of the present behavior of the MA glass composition with the other glass compositions, there is a strong suggestion that the effect of mixed‐modifier cations (MMCE) is having an active role in the durability of this glass.…”

“…The K-rich, the Na-rich and the Na-Ca glasses also studied by the authors were exposed to similar conditions and present a higher degree of surface attack by atmospheric moisture. 31,32 Hence, following the empirical nature of the previously suggested structural and compositional dependences, 32 the greater limiting factor of the alkali release from these surfaces and the lower proneness of the structure to interact with water molecules seems to be the network topology itself. Once more-and considering the other compared glass compositions-it is important to mention that this is a multicomponent silicate system, where the different oxide content (ie the cations) contribution to the response of the lattice when in contact with air moisture is known to play a complex structural role.…”

“…The simple ideas previously put forward to qualitatively account for the role of the network topology 32 (considering the current knowledge on the glass network and on the chemical attack by water) seem to be able to be extended to the present scenario:…”

“…All of these objects present a very good preservation state compared to others with compositions similar to the other produced replica material (Na-rich, Na-Ca-Si and K-rich glasses) and which surface alteration was already discussed elsewhere. 31,32 The latter were also aged under the same conditions and revealed a rather different (more pronounced alteration) behaviour. 31,32 Once more, this evidence supports the proposal made of the higher durability of the MA type studied, and contributes with long-term evidence to the good agreement with the models suggested as interpretative of the observed phenomena.…”