Glass Tempering Furnaces two

II. The traditional chemical toughening method The traditional technics of glass chemical toughening is the potassium nitrate is put in the stainless container to be heated at temperature 450 degree Celsius to be melt as liquid, the preheated glass sheets are immersed in potassium nitrate solution for 4-8 hours at temperature 450 degree Celsius to make K ions on glass surface exchange Na ions in solution. After ions are exchanged, glass sheets are taken out from solution, annealed and cooled to room temperature, then washed. Because the size of the K ions is bigger than the size of Na ions, during period of glass surface cooling shrinkage, the stress will be formed with the internal, thereby the strength of glass surface is increased. This method is called immersing. Glass Tempering Furnaces III. The coating method The coating method is that some metal salt solution is mixed with some homologous chemical reagent to be evenly coated on glass surface at room temperature, glass sheet is pushed into dedicated furnace to be dried, heated, and kept warm about 2 hours after reaching a certain temperature, then annealed, cooled to room temperature, taken out and washed.