Glass is among the most useful materials used in the packaging industry today. It is regarded as the most eco-friendly packaging material because it can be recycled over and over again without losing quality. In this article, we are going to discuss how glass bottles and glass jars are made along with the different glass bottle types.
But, before we go to the glass manufacturing process, let us first learn about the 3 most common glass manufacturing terminologies used in the container production industry in the next section.
The 3 most popular terms in glass manufacturing are gob, parison, and glass batch.
Gobs refer to cylinders or lumps of melted glass. Once the glass reaches a certain temperature in the manufacturing process, it is cut off using a shear blade and shaped into gobs. They are also called blobs of glass.
The formation of parisons comes next after the gobs are made. The molten gobs are sent to the parison mold, also called “blank”, to produce the pre-form of the glass bottles. In short, parisons are partially formed pieces of glass jars or bottles with finished necks.
Glass Batch
A glass batch is a mixture of the raw materials needed in making glass that is not yet melted. It is heated, melted, and cooled to make glasses.
Modern glass bottles and jars are made using the following:
Purer silica sand means lower iron content which allows for more control over the resulting glass bottle’s color. The purpose of limestone is to decrease the temperature under which the raw material mixture melts. Aluminum oxide and magnesium oxide are also frequently added to achieve better durability.
Lastly, cullet (recycled and crushed glass) is a highly-essential raw material in glass manufacturing that helps in minimizing the amount of energy and raw materials needed in making new glass containers.
Cullet has the same material composition as glass batches. It is added into the mixture because its melting characteristics inside the furnace help in accelerating the conversion of the glass batch into gobs.
Cullet is an energy-saving material that not only lowers the amount of energy required to melt glass batches but also helps in reducing the carbon footprint of glass. Glass batches may be composed of 25% to 60% cullet and the produced glass containers typically contain 70% to 74% silica sand by weight.
Now, let us proceed to the manufacturing process of glass containers.
Once the mixture is melted and formed into gobs, a well-timed blade is used to cut it to create gobs with equal weights before they undergo the forming process. A gob’s weight is very important in the creation of each glass bottle/jar. Molded glasses are created by feeding molten gobs into forming machines with the help of gravity. Pressure in the forming machine molds the glass bottle’s neck along with its general shape.
To form the bottle’s final shape, two different methods can be done: the Press and Blow formation and the Blow and Blow formation. The forming process followed depends on the type of glass container being made.
This method is the widely used process in manufacturing glass bottles. It makes use of an IS machine composed of different sections for producing same-sized containers simultaneously. Moreover, it is typically used to manufacture wide-mouth glass jars and bottles.
Below is a short simulation of the Press and Blow process:
While the Press and Blow process is used for wide-mouth containers, the Blow and Blow formation is used to manufacture narrow containers and those that require various neck thicknesses. It uses an IS machine too where gobs are also fed into molds through gravity. Only the formation of the parison is different.
Below is another video showing the simulation of the Blow and Blow process:
Regardless of what formation process was used, the same step follows next: the annealing process. This process cools down the glass containers at a uniform rate to eliminate internal stresses that could result in shattering or cracking. It rectifies stress to make the containers stronger.
The final step is subjecting the bottles/jars to thorough inspections to make sure that they meet the required quality control regulations. Any bottle that shows imperfections including misshapen areas, cracks, and bubbles is removed and then recycled as cullet.
Bottles and jars that have passed the inspection are sorted by type and size. After sorting, they are palletized and then shipped.
The last topic we are going to tackle is the different types of glass bottles.
This type of glass is clear and colorless. It absorbs the majority of UV light but little visible light.
Frosted glass is formed when any glass color is treated. The treatment process will give the glass a different feel and look.
Cobalt glass bottles are color blue which is due to the addition of cobalt oxide. It offers moderate protection from light.
Green bottles are created by adding copper, chromium, or iron into the melted mixture of raw materials. Chromium oxide produces emerald green to yellowish-green glass bottles. Blue-green glasses are produced by mixing chromium (green) and cobalt (blue).
This is a brown glass that can be produced by adding carbon, sulfur, and nickel into the mixture. It can absorb most radiation below 450nm wavelengths and thus can offer excellent UV radiation protection which is critical for drugs and beers.
A black glass bottle is normally produced using high concentrations of iron but can also include other additives like magnesia, carbon, copper, and iron.
Purple glass bottles and jars along with red and amethyst glass containers are usually made by using manganese or nickel oxides.
Copper and cobalt oxide are the common additives used in making blue glass bottles.
Opaque, or milk, glass is sometimes referred to as white or Opal glass. It is produced by adding calcium, phosphates, fluorides, zinc oxide, and tin.
The color of aquamarine glass containers is produced by the natural iron in sands or by adding iron into the mixture. The oxygen amount can be reduced or increased during the melting process to produce greener or bluish-green colors.
Aside from the glass colors, there are also other types of glass containers.
Bottles made from lead glass are softer so they are easier to cut. However, they cannot withstand high temperatures or sudden changes in temperature. They are usually used for making decorative figurines and glasses.
Soda, calcium, and silica make up soda lime glass bottles. The more the amount of silica there is in the mixture, the greater the resulting bottle’s resistance to thermal shock is. However, its thermal resistance is not comparable to that of borosilicate glass.
This is among the most widely used types of glasses. One reason is that it can resist breakage caused by changes in temperature. Thus, it can be used in lab equipment, glassware, and cookware.
This is also referred to as vitreous-silica glass or fused-silica glass. It is produced through the purification of crystalline silica that is found in rock crystal or sand either with flame or electrical fusion. Fused quartz bottles are highly transparent and are shock and weather resistant.
The last types of glass bottles we are going to discuss are those that are made from aluminum oxide. Aluminosilicate glass containers vary in composition but normally have between 20 to 40 percent aluminum oxide. Their properties are comparable to borosilicate glasses but they are more resistant to heat and possess better chemical resistance. This makes them harder to fabricate compared to borosilicate glass.
Now, you’ve learned that glass bottles and jars are not made using a single type of glass. Their different colors are produced using the right combination of different raw materials which also affects the resistance of the containers. If you are looking for a reliable glass bottle manufacturer, you can rely on Roetell. We offer different types of glass containers to accommodate your packaging needs.
We help you avoid the pitfalls to deliver the quality and value your glass bottle and jar need, on-time and on-budget.
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