How are glass bottles produced ?

If you would like to know how glass bottles are produced, then you have to follow the two main parts, one of them is for the raw material, and the other one is for its manufacturing processing.Although glass bottle is widely seen in our daily life,we could say that it is a simple product. The view above is focused on the angle of the consumer, however, if the prospective was based on the angle of the purchaser, even the engineers, we have to say that the glass bottles is not simple, not simple means that how is produced is not simple. Let s follow and move on based the tables and chart below:

 

Table 1: two main parts for how are glass bottles produced

Parts	Content
Raw Material of Glass Bottle	Proportion for Glass Bottle
Glass Bottle Manufacturing processing	6 steps Glass Bottle Manufacturing

 

 

1, Part One: Raw Material of Glass Bottle

From the below pie chart, you could see clearly that the raw material of the glass bottle is mainly including Soda Ash, Quartz Sand, Crushed Glass and other formula combinations. Their Proportion are 30%, 20%, 10% and 40% respectively.

As a matter of fact, if you were purchaser, sales or the marketing person, we think that the main raw material could be working for your question from your customers.

If you were an engineer, we must know much more, actually, there are 20 types raw material for our glass bottle, including soda ash, quartz sand, barium carbonate, sodium nitrate, lithium feldspar, zinc powder, cobalt powder, lithium feldspar, dolomite, potassium carbonate, aluminum hydroxide, sodium fluorosilicate, borax, clarifying agent, broken glass, etc.

 

Chart 1: Proportion of glass bottle raw material

 

 

For this point, sometimes, customers would ask factory to supply the COA, based on the industry regulation and our experince, glass factory would supply you the general, but not for the exactly, becuse of the formula, that is belong to a concept of business secret for glass factory.

 

 

 

2, Part Two: Glass Bottle Manufacturing processing

Sine year of 2005, we have been in the glass industry for more than 20 years. Based on the reality of our glass bottles manufacturing, there are 6 steps for glass bottle manufacturing, they are Batching, Melting, Forming, Annealing, Glass bottle Quality Checking and Packing. Pls see the 6 steps following:

 

 

Table 2: 6 steps for glass bottle manufacturing

No. of Steps:	Steps:
Step One	Batching
Step Two	Melting
Step Three	Forming
Step Four	Annealing
Step Five	Glass bottle Quality Checking
Step Six	Packing

 

2.1 Batching:

From the Part one, you could see that there are more than 20 type raw material. Apart the 20 types raw material preparation, we must take attention on the Precise Proportions, Purity, Granularity Control, Mixing Uniformity and Moisture Control. For the Precise Proportions, that means Recipe calculation is crucial and needs to take into account raw material purity, moisture content, cullet ratio and chemical composition fluctuations. Purity means that Iron content (affects color), heavy metal content (strict requirements for food/medical bottles), and refractory mineral impurities all need to be strictly controlled. Granularity Control means that affects mixing uniformity, melting speed and raw material conveying performance. Sand particle size distribution is particularly important. Mixing Uniformity means that using an efficient mixer to ensure that all raw materials are evenly distributed to avoid uneven melting or stone defects. Moisture Control means that too high a temperature will affect transportation and preheating, while too low a temperature may cause the risk of dust explosion.Pls see our automatical bacthing system picture as below:

 

 

 

2.2 Melting

After batching, then it is the Melting. The batch materials and cullet are placed in a furnace, where they are melted, homogenized, and clarified at temperatures exceeding 1550°C to produce molten glass that meets the requirements. This process is called glass melting. The glass melting process is a complex one involving physical and chemical reactions and phenomena.We make the the mixing material via the feeder, continuously and evenly pushed into the melting pool of the melting furnace. We call it Melting. For here, the core equipment is for the melting furnace and its feeder.

 

In the melting, it includes the Preheating, Melting in furnace, Clarifying, Homogenization and Cooling. In order to make you know it much more clearly, pls see the table below: 

Table 3: 6 steps for glass bottle manufacturing

No. of Steps:	Steps:
Step One	Preheating
Step Two	Melting in furnace
Step Three	Clarifying
Step Four	Homogenization
Step Five	Cooling

 

2.2.1 Preheating

It also named Silicate Formation, The batch absorbs heat, water evaporates, organic matter burns and decomposes, carbonates decompose (such as Na₂CO₃ → Na₂O + CO₂), and primary silicate melt is formed.

 

2.2.2 Melting in furnace

The temperature rises to about 1300°C - 1400°C, and the silicate melt further reacts with the remaining quartz sand to form a homogeneous glass liquid, but it contains a lot of bubbles and streaks.

 

 

2.2.3 Clarifying

It is called Refining too. The temperature is raised to the highest point (approximately 1500°C - 1600°C, depending on the type of glass). The viscosity of the glass is significantly reduced, and large bubbles produced by the decomposition of the clarifier rise and escape, carrying dissolved small bubbles ("bubbling" technology is often used to assist this process). At the same time, the degree of homogenization of the glass is improved

 

2.2.4 Homogenization

The glass is made highly chemically and thermodynamically uniform through thermal convection, furnace design or mechanical agitation.

 

2.2.5 Cooling

It is Conditioning, the glass flows through the flow tunnel and riser into the working pool, and the temperature is reduced to a viscosity range suitable for molding (approximately 1100°C - 1200°C).

 

 

2.3 Forming

 

When it comes to the glass bottle forming , we must focus on the 3 respects, they are main method, core equipment and the key details.

 

 

2.3.1 Main Method

Main Method for glass bottle forming includes the Blow & Blow and Press & Blow. From the words of Blow & Blow and Press & Blow, you could have got the feeling that they are a little complicated. Actually, they are not complicated. Why they are not not complicated ? You could understand it based on the angle of their weight, For the Blow Blow, it is a technology that is more tradittionla, it is for the heavy weight bottles; for the Press & Blow, on the contrary, it is a technology that could be right for the request of light weight bottles. Menwhile, from above, you could not think that the blow blow is too old to do bottles, because, there are still so many heavy bottle requests in the market. From the angle of market, we could know that the Europe market prefer the bottles that are produced based on Press & Blow.

 

2.3.1.1 Blow & Blow

From above, based on the angle of common people, we know that the Blow & Blow is mainly for bottles that are with heavy weight. However,taking the angle of  engineers, we could see it from its mouth of bottle. Blow & Blow is usually for small-mouth bottles , such as beverage bottles, beer bottles, and medicine bottles. For its forming, specifically speaking, it is raw material drops into the prototype mold, then the air is blown to form the bottle mouth and the prototype (inverted) , then the prototype is turned over to the forming mold, finally blow molding.

 

2.3.1.2 Press & Blow

Same as Blow & Blow, for the Press & Blow, the percpective of common people, they could  recognize it by the weight, if for light weigt, they could  say that is Press & Blow. But for the engineer or professional person, they must pay attention on the mouth of bottle. For wide-mouth bottles (such as food cans and large-mouth medicine bottles), they are belong to the craft of Press & Blow.For its forming, specifically speaking, it is raw material drops into the prototype mold, then the punch presses down to form the bottle mouth and the prototype, then the prototype is turned over to the forming mold, at last  blow molding.

 

2.3.2 Core Equipment

Core Equipment for glass bottle forming includes the feeder and IS machine

 

2.3.2.1 Feeder

The temperature of the glass liquid flowing out of the working pool is precisely controlled to the molding viscosity, and it is cut into droplets with precise weight and shape through the material mixing cylinder and scissor mechanism

 

2.3.2.2 Bottle making machine (IS Machine)

Modern high-speed bottle making machines usually have multiple independent molding units (such as 6-20 groups), each of which includes a prototype mold, a molding mold and its opening and closing, flipping, blowing and other mechanisms.

 

2.3.3 Key Details

Key Details for glass bottle forming includes the Drop Control, Molding, Molding Parameters

 

2.3.3.1 Drop Control

Weight accuracy (within ±0.5g), shape, and temperature uniformity are crucial to molding stability.

 

2.3.3.2 Molding

Complex design (affects bottle shape, wall thickness distribution, and stress), material (cast iron alloy) needs to be heat-resistant and wear-resistant, and surface treatment (coating) affects demoulding and bottle surface quality. The cooling system is precisely designed.

 

2.3.3.3 Molding Parameters

Air puffing/compression pressure and time, air blowing pressure and time, vacuum assist time, mold temperature, action sequence, etc. need to be finely adjusted and matched.

 

 

2.4 Annealing

It is a very crucial process that is very important to the quality of glass bottles. To know more about it, we could follow the aspects of its purpose,equipment and key details.Pls see as below:

 

2.4.1 Purpose:

To eliminate harmful residual stress caused by uneven cooling during the molding process, and prevent the bottle from breaking during subsequent processing, filling, transportation or use.Also you could understand by another direction, it is the process of heating a bottle with permanent stress to a temperature at which particles inside the glass can move, and using the displacement of particles to disperse the stress to eliminate or weaken the permanent stress.

 

2.4.2 Equipment:

Annealing furnace (continuous mesh belt annealing furnace)

Heating uniform temperature zone:** Reheat the bottle from the molding temperature (about 500°C) to the annealing point temperature (usually 560°C - 580°C, viscosity about 10¹³ poise).Insulation/stress relief zone: Keep at the annealing temperature for a sufficient time to allow the stress to relax fully.Slow cooling zone: Cool through the strain point temperature (viscosity about 10¹⁴·⁵ poise) at a strictly controlled and very slow rate (such as a few degrees per minute).Fast cooling zone: Cool to room temperature (<70°C) at a faster and safe rate.

 

2.4.3 Key details:

Annealing temperature curve: Accurately set according to glass composition and bottle wall thickness. An unreasonable curve will lead to excessive or uneven residual stress. Temperature uniformity in the furnace:The horizontal and vertical temperature differences need to be strictly controlled. Cooling rate:The slow cooling rate near the strain point is the key to determining the level of residual stress. Hot end coating: Organic tin or titanium compound solution is often sprayed at the entrance of the annealing furnace to form a protective film on the bottle surface to improve scratch resistance and strength.

 

For this processing, based on above, you could see that hot end coating is belong to it, sometimes, we could say that the hot end coating is processing togther with Annealing. According to our experience, if for large sacle glass factory like us, there is cold end coating. Actually, some of our new customers asked if our glass bottles are scratch proof, for this, as a matter of fact, glass bottle itself is no scratch proof, because the cold painting is no necessary for a glass factory, and many application circumstances is no request for that. However, if it was in the requested circumstances of application, that is necessary. If it was without the processing of cold painting, but it was in the requested circumstances of application, then your bottles would be scratched heavily and spoiled, especially for the bottles that are for the years recycled. But, for us , we can do the cold painting for you, then your bottles would be no any scratch, even for many years.

 

2.5 Quality Checking

Our glass quality checking are done based on the automatic checking (100% full checking), includes the online and offline checking.

 

2.5.1 Online Checking

Bottle mouth size checking, height, inner diameter, outer diameter, ovality, flatness of the sealing surface.

Wall thickness inspection: Non-contact laser or ray scanning.Dimensional profile Checking, Optical camera system checks bottle height, outer diameter of bottle body, verticality, crooked neck, etc.Defect detection: High-speed camera combined with AI identifies cracks, stones, bubbles, impurities, burrs on the die seam line, deformation of the bottle bottom, stains, etc. As a matter of fact, in this glass industry, for those small factory, they are doing the online checking by manhand, for scaled factories like us, we proceed it based on atomatical checking line, so we could call it 100% checking. Due to the different QC, if done by manhand, then there would be a lot of quality problem exised, so there would be big risk for the quality,. if done by our atomatical checking line, then the quality would be good and steady. Totally, we have 25 sets K-270A automatical cheking machines and 20 sets EBI autamatical camera for glass bottles Quality Checking.

 

 

2.5.2 Offline sampling Checking:

Offline samplling checking is mainly for the samples are checked in the lab of factory. Including Internal pressure test: Test the ability of the bottle to withstand internal pressure (such as beer bottles, carbonated beverage bottles).Thermal shock resistance test: Test the ability of the bottle to withstand sudden temperature changes.Internal stress resistance test: Quantitatively measure the residual stress level using a polarizing stress meter.Chemical stability test: Test the water resistance.

 

 

2.6 Packaging

Bottles that pass the inspection are packaged according to customer requirements.

Carton packaging: Load into cartons, and then stack cartons on pallets.

 

Pallet shrink film packaging:** Bottles are directly stacked on pallets and fixed with heat shrink film.