Degradation Mechanisms Basic Reactions in Water

At high pH values (in general above pH 9), another type of mechanism controls the degradation of glass hydroxide ions attack the bridging Si—O—Si bonds, which leads to dissolution of the glass network. 

Both reaction mechanisms, the ion exchange and the network dissolution, compete with each other in natural conditions. In the laboratory, those conditions can be manipulated to clearly favour one mechanism over the other. 

The reactions can be quantified even before visible damage occurs by analysing the components dissolved in the solution (preferably by ICP-AES) or by characterising the altered glass surface (with surface-sensitive techniques such as X-ray photoelectron spectroscopy (XPS), and Infrared-spectroscopy (IR)). 

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