Glass needs to cool slowly and in a controlled manner so that internal stresses do not develop, stresses can make the glass crack. The annealing process is a gradual cooling of a hot piece of glass until it reaches room temperature. It’s one of the most important steps to secure a perfect final result. The process consists of three stages:
Stress Release + Annealing + Cooling
Each glass type and each stage have its own temperature and duration, and these must be calculated. Please remember that the calculations are based on basic glass theories and the reality can vary. When combining different types of glass and/or different thicknesses, we recommend increasing the time in each stage. To find the correct time we suggest making several tests before going into live production of high value glass pieces.
Annealing diagram
The diagram shows an example of a typical annealing process.
Annealing calculator
To calculate the optimal annealing process for a project, please specify the product that is used and in what thickness.
Measuring the glass thickness
The measurement point for thickness should be taken at the greatest cross-section of the glass object (see Example 1 below).
However, if the glass object is formed with enclosed air that prevents free internal circulation (see Example 2 below), the outer diameter of the glass object should be used instead.
As a general guideline, if the opening or hole is smaller than 3 cm (1.2 inches), the outer diameter should be considered as the effective thickness.
