…. Continuation of From idea to finished product from glass Part 1
The production process of the pressed glass article begins
The mould is built in to the press. Now the actual production process begins. It can be sweaty work at the furnace, with temperatures reaching up to 1300 degrees. According to the shape and size of the material of the pressed glass product, the appropriate raw glass rods must be selected. There are glass rods with different diameters. The bigger the glass article, the thicker the glass rods. The diameter of the glass rods can be as high as 44 mm. Depending on the type of glass or even the colour of glass, there are different requirements to be considered when processing. The glass rods are then heated in the oven. As soon as the glass rod is soft and is suitable for the pressing operation, it can be kept in the open press. The press closes and presses the product accordingly. Throughout this process, the mould is permanently heated by flame so that you have an appropriate temperature necessary for the successful finalisation of the product. During the pressing process, there can be excess glass from the edge of the article. When the item is then pressed, the connection to the glass rod is broken with a special pair of scissors. The glass rod is then held to the heat for the next pressing operation in the oven. The pressed article is then removed with forceps from the opened mould.
The cooling process of glass pressed articles
The product is attached to a so-called cooling belt for the cooling of what is still a very hot but already solid item. The conveyor belt moves in a very slow pace in the cooling furnace and cools the product within a period of about 2 hours. This is an important process. Glass expands when heated and contracts when cooled. This creates stresses in the glass, which varies according to articles. These stress conditions also often require an additional process of reducing tension in a special „relaxation oven“. This means that the article is heated again a few days later after complete cooling and is slowly cooled by a special cooling curve.
Thus excessive stresses in the glass will be removed. This is necessary for further processing, such as drilling a hole, sawing, etc. We have therefore described the actual process of first serial production of a glass article in today’s blog e.g. of a glass bead or a glass lens. The third section then goes to a no less important work section – quality control, finishing and final inspection of the finished product