Soaking glass in heat allows the temperature to become even throughout. This is a way of relieving stress at certain points in the item so it won’t crack or fracture. Heat soaking is usually done before and after the formation of the object in order to make it most malleable and durable.
This is the process of cooling a glass object, after it has been heated up and form into its desired shape. This must be done very carefully and slowly so as not to put any added stress on any of the weak points in the material. Once the glass has cooled to a certain temperature, it will be soaked in heat again to further reduce any underlying stress.
Maintaining Accurate Temperature
The viscosity of the glass is extremely important to the overall process in order to keep the object at its most durable and to ensure the final product is perfect. The annealing point is the temperature at which the glass is cooled, η = 10^13. At this point, the glass is too hard to deform as explained in http://bluesky-fencing.com.au but still within the range of usability. At η = 10^14.5, the strain point, the glass is very flexible and must be handled with caution. Also, the cooler the glass is, the less time it will take for stresses to relax. At the annealing point, stresses can take no more than ten minutes to settle. At the strain point, it can become a matter of hours.