Production - Making Container Glass

Container glass is made of simple natural ingredients. The mostcommon virgin materials are silica sand, soda ash and limestone*. These

materials are mined all over North America, and there is a plentifulsupply available. The following pie chart illustrates the basic list and

the minor ingredients required for container glass:

Silica SandSoda Ash

LimestoneAlumina-SilicateSalt Cake

Minor Ingredients

An energy and cost effective alternative when making container glassis the addition of a variable percentage of crushed furnace-ready

recycled container glass or cullet. This can be added to the materialbatch to reduce the amount of virgin raw materials used. The

percentage of cullet used varies based on the consistency and qualityof supply. Glass furnaces prefer a stable blend. The use of recycledcontainer glass conserves virgin materials, while at the same timereducing solid waste by diverting glass containers from going to

landfill. Also, as cullet has a lower melting temperature than virginmaterials there is an energy savings when recycled container glass is

used to make new glass container.* Virgin materials refer to newly mined ingredients whereas raw materials includes cullet.

Senior

Container glass can be produced in many different colours. The most commonbeing, flint (clear), amber (brown) and various shades of green and light blue.

The raw materials required to make the different colours of glass are classifiedas minor ingredients in the pie chart. Specifically, the materials for each colourare:

Amber: Iron Sulphide

Green: Iron-Chromite

Light Blue: Cobalt

Flint: is colourless glass, also called clear.Each colour of glass serves a specific function for the companies that buy andfill the glass containers with food, beverages and other products. The colour

choice is made by the company buying the package, not the manufacturer of theglass container.

A certain glass colour may be used for marketing purposes to make the productlook more appealing to the consumer. Flint, or clear container glass, may be

preferable to enable the consumer to view the product inside. Another colourmay be chosen for technical reasons. For example, the brewery industry tends

to use amber glass to protect beer against damage by ultraviolet light. Too muchexposure to light can make the beer go skunky, meaning that it loses the

quality of its taste.

Something to think about: Container glass is a reference to the materialwhereas glass container is a reference to the package.

Glass container manufacturing is unique among packaging materials as the makingof the material and the manufacturing of the package is one continuous process.

The glass container manufacturing process begins when virgin materialsrequired for the manufacturing process are received and stored in huge silos.These materials are then transferred through a gravity feed system to aweigher and mixer to ensure homogeneous melting, where they are mixed withcullet (crushed furnace ready recycled glass containers). The mixture isconveyed to a batch storage bin where it is held until dropped into the feederto the furnace where it is melted.

The furnace most commonly used is a continuous regenerative furnace capableof reaching temperatures in excess of the 1500C. This high heat is needed tomelt the ingredient materials, producing between 100 and 400 tonnes of glasscontainers per day. As the materials melt together container glass is formed;it passes to the front of the furnace and eventually flows through a throatleading to the refiner. In the refiner, the molten glass is heat conditioned fordelivery to the forming process; at this point the container glass is a fluidsubstance, flowing like lava.

Once the glass is shaped into a container, it is fed to a lehr oven for annealing,which is the removing of any unwanted stress areas in the glass container. Itis then inspected and prepared for shipment to market. Any damaged ordefective glass is transferred back to the batch plant to be used as cullet.The flowchart diagram below summarizes the glass container manufacturingprocess.

Raw Materials

Melting Furnace

GlassForming Annealing Inspection

Cullet Crushing

PackingShip to

Market*

* The market refers to the company that fills thebottle or jar with product. It is then shipped tostores where your involvement starts.