Lab Watch Glass

Batching of raw materials
The main components, comprising silica sand, calcium oxide, soda & magnesium are weighed and mixed into batches to which recycled glass (cullet) is added. The use of 'cullet' reduces the consumption of energy. The materials are tested and stored for mixing later under computerized control.

Melting of raw materials in the furnace
The batched raw materials pass from a mixing silo to a five-chambered furnace where they become molten. Temperatures in the furnace reach upto 1600°C.

Drawing the molten glass onto the tin bath
The molten glass is then "floated" onto a bath of molten tin at a temperature of about 1000°C. It forms a "ribbon" which is normally between 5 and 6 mm. By suitably drawing the glass through a complex process involving top roll machines, ribbon thickness in the range of 1.9mm to 19mm can be achieved. The glass, which is highly viscous, and the tin, which is very fluid, do not mix and the contact surface between these two materials is perfectly flat, giving the term "flat" glass to the final product.

Cooling of the molten glass in the annealing lehr
On leaving the bath of molten tin, the glass - now at a temperature of 600°C - has cooled down sufficiently to pass to an annealing chamber called a lehr. The glass is now hard enough to pass over rollers and is annealed, which modifies the internal stresses, enabling it to be cut and worked in a predictable way ensuring flatness of the glass. As both surfaces are fire finished, they need no grinding or polishing.

Quality checks, automatic cutting, and storage
After cooling, the glass undergoes rigorous quality checks. It is then cut into sheets of sizes varying upto a maximum of 6000mm x 3660 mm which are, in turn, automatically stacked, stored and ready for transport.