Dating glass by color archaeology site dating 2016 asia link
The deterioration of the glass surface is generally known as .The chemical and physical properties of the burial environment and the composition of the glass itself are the main factors that determine the rate of deterioration of glass in the ground.Another theory states “that as large sodium or even larger potassium ions are replaced by protons the physical stress on the structure causes the surface layer to split.” This allows water to get through to the fresh glass underneath and the process is repeated.The decrease in volume caused by the leaching of ions can lead to microporosity of the surface layer, which in turn might cause the weathering layers.This is because water is the primary cause of deterioration of glass.The exposure of glass to moisture causes alkali ions in the glass network to be slowly leached out and replaced by hydrogen ions from the water., which is a rainbow-like effect on the surface of the glass similar to a thin layer of oil on a water surface.
Pitting often occurs simultaneously at individual sites throughout the surface of a fragment.
In alkaline environments the silica network is attacked, eventually causing the total dissolution of the glass.
Although the chemical processes of glass deterioration have been extensively studied, they are not yet entirely understood and cannot be predicted.
This leached layer is referred to by several different terms: alkali-deficient layer, silica-rich layer, or hydrogen glass. Interestingly, it re-occurs in a cyclic manner, with additional layers being formed again, every few years.
Distinct layers can often be seen, and as they build up, the weathering crust gets thicker and thicker.