Why do some glass candle holders need to be reannealed?
Sunny Glassware is a manufacturer specializing in the design, manufacturing and export of glass candle holder. Our product line ranges from hand-made to machine-made, and has produced a wealth of products, such as glass candle holder, glass cups, borosilicate glass, shot glasses, vases, glass bowls, candle holders, stemware, ashtrays, tableware, drinking glasses, etc. . There are more than 4,000 different styles of glassware for all daily use.
There are many techniques for making glass candle holder, such as machine blown glass, manual blown glass, etc. So why does glass candle holder need to be annealed after it is made? Today, let Sunny Glassware talk about the reasons and methods of annealing.
What is annealing of glass candle holder?
After the production of a glass candle holder is completed, there are temporary and permanent stresses. If it is a temporary stress, it will disappear as the temperature changes, but a permanent stress will not be able to withstand an explosion when the temperature changes.
In order to prevent explosions, high temperature treatment is required. Without annealing treatment, it is easy to burst during use. Therefore, in order to eliminate permanent stress in the glass, it will be safer to use after a high-temperature stage treatment.
Annealing temperature and method
In order to eliminate permanent stress, the glass must be heated below the glass transition temperature, then kept warm and homogenized. It is to eliminate the temperature gradient and relax stress in various parts of the glass. The annealing temperature for most glassware is 550+20℃. The annealing temperature of bottles and cans is 550-600℃. The annealing process can be divided into four stages: 1. Heating stage, 2. Soaking stage, 3. Slow cooling stage, 4. Rapid cooling stage. This curve is called the annealing curve.
Glass candle holders of different craftsmanship will have different annealing processes.
Some glass candle holders are directly put into the annealing furnace for annealing after being made, which is called one-time annealing. However, some glass candle holders need to be annealed after cooling, which is called secondary annealing. So not all glass candle holders must be annealed twice.
