Art glass has considerable plasticity, and the plastic deformation of art glass temperature range is also large. The plastic characteristics of art glass are conducive to glass forming.
Art glass heat treatment of high pressure glass, high temperature glass, all kinds of glass in general, annealed glass than quenched glass chemical stability. This is because the density of annealed glass is larger than that of quenched glass and the network structure is closely contrasted. After quenching, the surface of glass is in a high compressive stress condition, which has a counteracting effect on the loose structure of the surface. Therefore, the chemical stability of glass with high quenching degree may be higher than that of annealed glass. Annealing has two methods: bright flame and dark flame.
The former refers to the annealing of glass products in furnace gas. At this moment, the alkali metal oxides on the surface of the glass can be neutralized with the acid gas in the furnace gas, and constitute the "white frost". When the "white frost" is removed, the content of alkali metal oxides on the surface of the glass decreases, and then the chemical stability of the glass products. On the contrary, it is assumed that the dark flame annealing will lead to the enrichment of alkali on the surface of the glass, and the chemical stability of the glass decreases with the increase of the annealing time and the progress of the annealing temperature.
In order to improve the chemical stability of glass products, factories sometimes use fuel with high sulfur content for flame annealing or add SO₂ gas, ammonium sulfate, aluminum sulfate and other salts to the annealing furnace. During the annealing process, borosilicate glass will be divided into silicon-rich oxygen phase and sodium-boron phase. After phase separation of art glass by heat treatment, if an island drop spherical structure is formed, the sodium-boron phase is surrounded by silicon-rich oxygen phase, so that the soluble sodium-boron phase is protected from the corrosion of the medium, the chemical stability of the glass will advance.
Therefore, attention should be paid to the connection between the chemical stability of art glass and the annealing principle in glass with higher B₂O₃ contents.
