Three Steps In Glass Bottle Production

Three Steps In Glass Bottle Production

You may have wondered what goes into the production of Glass bottles and glass jars.

Today's blog will answer all of your questions about glass bottle and jar manufacturing.

Glass Container Production in Modern Factories passes through three main stages:

• The Batchhouse stage deals with the handling of raw materials.
• Hot End stage is responsible for the production and moulding processes -- the forehearths, forming machines and annealing furnaces.
• Cold End stage - deals with product inspection and packaging equipment.

Read about these three phases in detail.

Batch House Stage of Manufacturing of Glass Bottles

Stage 1: Collection of Raw Material

Glass bottles and jars for packaging are produced using natural raw materials, primarily silica and soda lime. Each of these materials serves a distinct purpose: soda reduces the melting point of sand, while lime contributes to the hardness, shine, and durability of the glass. Cullet, which consists of broken glass collected from rejected bottles by manufacturers or from recycling centers, bottle banks, and curbside collection systems, plays a crucial role in the production of glass containers.

Stage 2: Preparation of Batch

The preparation of the batch begins with a grinding machine, where raw materials, cullet (shredded glass pieces), and decolourisers/colourisers are finely ground. Following this, the ingredients are carefully weighed to ensure the correct proportions before being combined. This mixing process is typically carried out in a mixer until a uniform mixture, referred to as a batch or frit, is achieved. Once mixed, these batches are stored in large vertical silos prior to being introduced into the kiln. The batch then proceeds to the next stage of melting in a furnace.

Hot End stage of Manufacturing of Glass Bottles

Stage 3: Melting in Furnace

In a furnace maintained at roughly 1748°C, the mixture steadily melts. This furnace runs continuously, 24/7, with an estimated lifespan of around 1012 years. The raw materials fed into the furnace transform into glass containers within approximately one day. The molten glass travels to the forming machine via distribution channels known as forehearths. At the end of these forehearths, the glass stream is segmented into pieces that are meticulously regulated in terms of weight, shape, and temperature.

Stage 4: Forming at Present

Glass bottles are produced using two techniques: the Blow and Blow (B&B) method and the Narrow Neck Press and Blow (NNPB) method. In both methods, molten glass is cut into a cylindrical shape known as a gob, using a blade at temperatures ranging from 1,050 to 1,200 degrees Celsius. The weight of each gob is carefully measured to ensure it's suitable for bottle production. Both B&B and NNPB processes begin with the gob falling by gravity through chutes into blank molds. These molds are then closed tightly and sealed from above with a baffle. The key difference between the two methods is that in the B&B process, air is used to blow the parison into shape, whereas in the NNPB process, pressing is used to form the glass container parison. If you're interested in reading more about these processes, feel free to leave a comment or get in touch using the links provided below.

Stage 5: Annealing

In order to ensure that a newly-formed glass vessel is strong, it needs to be heated and then cooled in an "annealing larh", a tunnel kiln. It can take between 30 minutes and 2 hours. The glass will be weakened if the cooling is uneven. The annealing lehr, also known as an annealing furnace in the industry, heats up the vessel to 580degC. It then cools it for between 20-60 minutes depending on the thickness.

The Lehr is an automated conveyor that has different temperature zones. Glass bottles and jars are treated with a topcoat that is applied hot before they enter the lehr, and then a second coating when the glass cools down after leaving the lehr. The glass container production process is complete.

Cold End stage of Manufacturing of Glass Bottles

Stage 6: Coatings

On glass bottles and jars, there are usually two types of surface coatings. The first is applied at the hot end before annealing and the second at the cold end right after annealing.

The hot end is coated with a thin layer of tin dioxide using an organic compound that's safe or inorganic stannic chloride. Tin-based systems aren't the only option, but are the most commonly used. Titanium tetrachloride and organo titanate are also options. In all cases, the coating improves the adhesion of the cold end coating to the glass surface. A layer of polyethylene is applied to the cold end via an aqueous solution.

The containers are coated so that they do not stick together while moving along the conveyor. The coating makes the glass virtually scratch resistant. It is made primarily of special glass. Coatings that reduce surface damage are sometimes referred to as hardening coatings and less often as coatings with retaining strength.

Stage 7: Quality Inspection Machines

Both automatically and manually, all glass containers are checked for various defects.

Glass containers can have a variety of defects. Glass containers can be damaged by small checks or foreign objects, such as stones.

Air bubbles in the glass (i.e. Bubbles in the Glass and excessively thin walls are also defects. A tear is another common glass container defect. If the plunger or the mould is misaligned, or they are not heated at the right temperature, then the glass will stick and break.

The inspection equipment not only rejects defective containers but also collects statistical data and transmits it from the hot end of the forming machines to the operator. Computer systems track down the mold from which the glass container is made and collect incorrect information. The container's mould number can be read by the mold that produced it. Containers that don't meet the standard are automatically rejected. They will be returned to the furnace.

Stage 8: Secondary Processing

Glass container manufacturers offer additional services, such as labeling. The Applied Ceramic Marking process (ACL) is unique to glass. The screen-printed decoration is applied on the container using glass enamel paint, and then baked. Coca-Cola’s original bottle, which is well-known as an example, is one of the best examples.

Stage 9: Packaging

Glass containers are packaged in different ways. In Europe, bulk pallets are popular, as they can hold up to 4,000 containers. Automated machines (eg, palletizers and sheet-layer separators) are also available. Boxes and hand-sewn bag are also options. New "in-stock" items are then tagged and stored in a storage facility before being shipped.