The Story of Glass

Join us on a journey as we explain glass making

From sand to sophistication


For all of its versatility and splendour, no one really knows how glass was discovered. It’s very possible that glass, like the fires that would have forged it, was discovered by happy accident. No matter the reason, the attraction to this hard, shiny, magical material was immediate. As a result, humanity has been refining the manufacturing process of glass for many millennia.

Today, glass is recognised as a trusted, versatile, and an infinitely recyclable packaging choice. And as Africa's leading glass packaging manufacturing company for more than 70 years, Consol is synonymous with glass packaging.

Join us on a journey as we explain glass making; a magical, passion filled process to produce nature's best packaging. 


Batching


Stored in large silos, the ingredients – sand, soda ash, limestone and cullet (also called recovered glass) – are carefully measured and delivered to batch mixers, according to pre-programmed recipes. Consol's batch houses are among the most modern in the world, with cutting-edge technology to ensure that the mixed material delivered to our furnaces meet our stringent quality standards.

Circle Batching

Melting


Melting glass begins with a process where a batch is continuously fed into a furnace at a temperature of approximately 1,500°C. This is known in the glass industry as the “hot end”. After 24 hours, the raw materials will have been melted down into molten glass. The red-hot liquid glass is then drawn from the furnace through a submerged throat.

From the furnace, the molten glass makes its way to the refiner area, where it is cooled to approximately 1,200°C to correctly maintain the flow of the molten glass, while simultaneously ensuring the quality of the end product.

From the refiner, the forehearths deliver glass to the individual bottle-making machines. The molten glass enters the feeder and flows through cavities in an orifice plate. Streams of glass are cut into gobs of a predetermined weight. These gobs are then guided into the individual moulds of the bottle-making equipment, as part of a process known as forming. 


Forming


Whether intended to produce a jar or a bottle – the process is the same – a gob of glass falls into a blank mould to produce a parison (a hollow tube). During this stage the opening of the container is moulded into its finished shape, but the body of the container is much smaller than its final size.

From there, one of two methods are used for making a glass container. The first, the Blow-Blow process, is used for narrow-neck containers. The second process, the Press-Blow method, is used for jars and tapered narrow-neck containers.

The newly formed container is then transferred to the annealing oven, known as a lehr. The external surface of the bottle is first coated with a thin layer of tin oxide to strengthen it. In the lehr, the bottles are cooled slowly from 600°C to 100°C. Doing so prevents uneven cooling, relieves stresses within the bottle and ensures that it is stable and safe to handle. 

When the bottle exits the lehr, it is cooled and reaches the "cold end" of the factory. But before leaving the lehr, the bottle’s external surface is coated with polyethylene wax to protect the surface of the glass and prevent scuffing between bottles. 

Circle Forming

Inspection


All glass containers manufactured by Consol undergo multiple quality assurance tests and inspections, to ensure that they comply with strict quality standards.  

Bottles also undergo further visual inspection by sophisticated, high-resolution camera equipment, as well as trained specialists. Rejected containers are sent to the recycling operation to be turned into cullet and re-enter the production process.

At Consol, we pride ourselves on our commitment to manufacturing excellence, quality and the safety of our employees, customers and consumers. We are committed to achieving and maintaining compliance across all relevant standard specifications, and undergo regular audits accordingly.

  • OHSAS 18001: An international Occupational, Health & Safety Standard
  • ISO 14001: An Environmental management system standard
  • ISO 9001: Recognised standard for quality management
  • FSSC 22 000: Food Safety Certification 


 

Learn more about the Story of Glass

Manufacturing and Technical Expertise

Product and Process Innovation