There are several steps involved in the production of glass for the alcohol, beverage, and food industry. Overall, the process of making glass bottles is highly automated and requires specialised equipment’s to ensure the bottles are of high quality and consistent shape and size.
Step 1- Raw Material Preparation
The process of making glass bottles begins with the selection of raw materials. These raw materials, which include sand, soda ash, limestone, and other minerals, are carefully chosen to ensure that the finished bottles will be strong and able to withstand the pressure of carbonated beverages, as well as for other characteristics, such as clarity of the glass and whether specific colouring is required, like for wine bottles which have different shades of green. Cullet (recycled glass) may be used also in the mix, though the clarity of the finished glass can vary. The raw materials are regularly checked for quality and any foreign materials before they are mixed together.
Step 2- Batching and mixing
The mixing portion is important to ensure that all batches of the glass bottle are produced to the same quality. The mixture portions must be accurate, therefor specialised equipment’s are utilised to regularly test that the specific ratio is consistent before being melted together. Any irregularities must be caught at this stage, as once the glass is melted, it cannot be undone. The batches that are inconsistent are discarded with and recalibration of the specialised equipment takes place.
Step 3- Melting
Next, the glass batch is melted at a high temperature, typically around 1700°C, to create a liquid homogenous glass mixture, called molten glass. The melting process is carefully controlled to ensure that the molten glass is free of impurities and has the desired characteristic properties.
The furnaces generally run 24 hours a day 7 days a week to ensure a stable temperature and to reduce any energy waste. During this week hundreds of tonnes of glass will be processed through the furnace.
Step 4- Blow Forming Process
The process of blowing glass dates back thousands of years and has been used to create a wide variety of objects, including vases, drinking glasses, and decorative pieces. In antiquity the glass blower would have gathered the molten glass gob at the end of a long metal tube called a blowpipe. The glass blower then blows into the blowpipe, using their breath, to inflate the melted glass gob into a bubble. While the glass is still hot and pliable, the glassblower can use a variety of tools to shape the glass into the desired form. There are many different techniques that can be used by a glass blower to blow & shape the glass including blocking, marvering, and swinging. The specific techniques used depend on the type of object being made and the desired final shape. Blown glass by an individual is a fascinating and delicate art form that requires a high level of skill and precision and still used today to create beautiful and unique pieces of glassware that are highly prized by collectors, though is not economical for the modern-day large scale commercial business.
In the modern age of glass bottle manufacturing, once the molten glass has been melted, a precision machinery cuts out a perfectly weighted piece, called a gob, with a blade and with the help of gravity it falls into a mold, typically made of out stainless steel, to begin the blow forming process. There are two types of blow forming process, each with their own unique applicability.
Method 1 - Blow and Blow Process / Double Gob Feeder
For narrow glass bottles, such as beer, wine, sparkling water, or soda, as well as other products such as perfume and cosmetics, the Blow and Blow Process is generally used.
The Blow and Blow process is a method of manufacturing glass bottles that involves gathering the molten glass gob at the end of a blowpipe and with the assistance of compressed mechanical air, the gob is blown up to form the neck and the basic shape of the bottle, also known as a parison (a hollow, pre-form shape). The parison is then flipped to an upright position and transferred to a second station where it is mechanically blown again inside the mold of the desired bottle shape. This process is also known as Double Gob Feeder or Double Gob Process.
The Blow and Blow process is a faster and more efficient method than traditional glassblowing techniques, as it allows to produce larger quantities of bottles in a shorter amount of time.
Overall, the blow and blow process is a complex and highly technical method of manufacturing glass bottles that requires a high level of skill and precision. It is an important part of the glass industry and is used to produce many of the bottles that we use in our daily lives.
Method 2 – Press and blow process
For wide-mouth glass containers, such as glass vases, glass candle jars, storage jars or milk bottles, the Press and Blow Process is preferred. Overall, this process is typically used for making small to medium-sized containers.
Similar to method 1 where there are 2 stations involved in the blowing process, the Press and Blow instead uses a plunger in the 1st step to stretch the molten glass gob into a basic shaped parison, and finally it is flipped right side up, placed within the mold with the desired shape and mechanical compressed air is used to shape it to the correct proportions.
The Press and Blow process is a relatively fast and efficient method of manufacturing glass containers, and it is widely used in the glass industry.
Step 5- Annealing
Annealing is a process that is used in the production of glass to relieve internal stresses and increase the material's toughness and durability. It is typically used to improve the dimensional stability of the glass bottles and to make them less brittle.
During the annealing process, the glass bottles are heated to a temperature above its "annealing point" and is then slowly cooled to remove the stresses that have been introduced during the manufacturing process. The “annealing point” of a particular type of glass is the temperature at which it becomes soft enough to be reshaped without breaking.
There are two main types of annealing that are used in glass manufacturing: full annealing and surface annealing. Full annealing involves heating the entire piece of glass to the annealing point and then slowly cooling it, while surface annealing involves heating only the surface of the glass to the annealing point and then cooling it.
Annealing is an important step in the production of glass, as it helps to improve the strength and durability of the material, making it less prone to breaking or cracking. It is used in all glass products manufacturing, including but not limited to, automotive glass, architectural glass, and scientific instruments.
Step 6- Quality Check (QC)
There are several quality checks that are typically performed on glass bottles once they have been formed. Some of the most common checks include:
Visual Inspection: This is the first step in the quality control process, and it involves looking at the bottles to check for any visible defects such as cracks, chips, or uneven walls. This is typically done by an experienced operator on the production line using special lighting and magnification devices.
Dimensional Inspection: This involves measuring the dimensions of the bottles to ensure that they meet the specified tolerances for the product. This might include measurements of the bottle's length, width, height, or volume.
Weight Inspection: The weight of the bottle is also checked to ensure that it meets the specifications.
Wall thickness inspection: Wall thickness measurement is also an important check to ensure that the bottle is able to withstand the specified weight and pressure. It also prevents the bottle from breaking or cracking while filling, shipping, and handling
Hydrostatic pressure test: This test is done to ensure that the bottle is able to withstand the pressure that it will be subjected to during use. A sample bottle is filled with water and pressurized to a specific level to check for any leaks or cracks.
Inspection with X-Ray Machine: for certain types of containers which contains multiple layers, or for food and medical packaging, X-ray inspection is a common method to inspect for internal defects or foreign objects.
It should be noted that the specific quality checks performed may vary depending on the type of bottle and the end use of the product. All discarded glass is reused as cullet.
If there is no decoration required prior to filling, step 7 is skipped, and the bottles are packaged and shipped out to the clients.
Step 7- Decorating Glass Bottles
Once the bottles have been inspected and cleaned, they are typically decorated with labels or other markings to identify the contents and brand.
There are several methods for decorating glass for commercial use, including using decals, printing directly on the glass, and sandblasting.
Decals are adhesive designs that can be applied to the surface of the glass. They can be made of paper or vinyl and are often used for temporary or semi-permanent installations. Decals can be printed with a wide range of colours and designs and can be easily removed without damaging the glass.
Printing directly on the glass is another option for decorating glass. This method involves applying ink or paint directly to the surface of the glass using screen printing or digital printing techniques. The ink or paint is then cured to make it permanent.
Lastly, sandblasting is a technique that involves using a stream of sand or other abrasive material to etch a design onto the surface of the glass. Sandblasting can be used to create a frosted or textured finish on the glass and is often used for decorative or privacy purposes.
Step 8- Packaging and delivery
There are a few different ways that glass bottles can be packaged for delivery after they are made in a manufacturing plant. One common method is to pack the bottles into corrugated cardboard boxes. These boxes are designed to provide protection for the bottles during transport, and they can be easily stacked on top of one another for efficient storage and shipping.
Another way that glass bottles can be packaged is by using shrink wrap. This method involves placing a plastic shrink-wrap film around groups of bottles and then heating the film so that it shrinks and tightens around the bottles, providing a secure fit. Shrink wrap packaging is also efficient as it is easy to stack and can be customized to fit specific number of bottles in order to avoid movement and breakage during transport.
Another method is to use crates, these crates are specially designed to fit bottles and provide extra protection during transport. They are also easy to handle and stack for efficient storage and shipping.
In addition to these methods, it is also common for manufacturers to include additional packaging materials such as foam inserts or packaging peanuts to further protect the bottles during transport.
Ultimately the packaging of glass bottles can vary depending on the type of bottle, the quantity that needs to be shipped and the destination, to ensure the safety and integrity of the product during transportation.
Conclusion
In summary, the process of making glass bottles involves melting raw materials, pouring the melted glass into a mold, cooling and annealing the glass, inspecting, and cleaning the bottles, and decorating the bottles with labels or markings. This process is highly automated and requires specialized equipment to ensure the bottles are of high quality and consistent shape and size.