Characteristics of glass and metal can packaging

Currently, glass packaging and cans are widely used for containing food products. Let’s explore the characteristics of glass and can packaging in the following article.

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1. Concept of glass and can packaging 

Packaging made from glass is called glass packaging.

Glass is considered a premium material. Its characteristics give it a high-quality appearance and distinctive visual appeal. Glass has been used for centuries and is considered one of the best and most attractive packaging materials for containing premium champagne, fresh fruit juice, and other products.

Can packaging is a type of upright cylindrical packaging made from metal.

2. Characteristics of glass and can packaging 

2.1 Characteristics of glass packaging 

The properties of glass can vary depending on the impurities and the amount of additives selected during the glass-melting process.

a. Light transmission

One of the most distinctive characteristics of ordinary glass is its transparency to visible light, although not all types of glass have this property, as it depends on the impurities present. The light transmission of glass in the ultraviolet and infrared radiation ranges varies depending on the selected impurities.

b. Visible light

The transparency of glass to visible light is due to the absence of electronic transition states within the wavelength range of visible light. This characteristic is relatively uniform across the visible spectrum rather than being limited to a narrow wavelength range.

c. Ultraviolet

Ordinary glass generally does not allow light with wavelengths below 400 nm, or ultraviolet (UV) rays, to pass through. This is due to the addition of compounds such as soda ash (sodium carbonate). Pure SiO₂ glass, also known as quartz glass, does not absorb UV radiation and is used in applications requiring transparency within this wavelength range, although it is more expensive than ordinary glass. Cerium can also be added to glass to increase its ability to absorb ultraviolet radiation, including biologically harmful ionizing radiation.

d. Infrared

Glass can be manufactured to a level of purity that allows hundreds of kilometers of glass to remain transparent to infrared wavelengths when used in optical fibers. Large amounts of iron are used in certain types of glass to absorb heat, such as heat-absorbing filters used in film projectors.

e. Refractive index

The refractive index of glass can be changed by adding different components. Lead-containing glass, such as lead crystal or flint glass, is more “brilliant” because the added lead increases the refractive index and creates a more noticeable sparkle. Barium can also increase the refractive index. Thorium oxide gives glass a very high refractive index and has been used to produce high-quality prisms.

f. Melting temperature

Like other amorphous solids, glass does not have a specific melting point. Sodium is generally added to lower the melting temperature of glass. The addition of soda or potash can sometimes lower the melting temperature even further.

g. Electrical conductivity

The electrical and thermal conductivity of glass can be modified by adding boron, such as in Pyrex glass.

 

2.2. Characteristics of can packaging 

a. General characteristics of tin-plated steel cans

• The steel manufacturing process is relatively complex and has a high production cost.
• Mainly used for packaging foods such as vegetables, fruits, meat, and fish.
• Used cans cannot generally be reused for food packaging or other purposes. They are mainly recycled to produce steel materials.
• Used cans can degrade in the environment, but the process is very slow.
• Direct inkjet printing is expensive, so paper labels are commonly used instead.
• Tin plating is not applied to cans manufactured using drawing and deep-drawing processes because the tin coating can be damaged. If both the inner and outer surfaces of each can are tin-plated, the cost of the cans would increase significantly.
• Tin-plated steel cans are coated with varnish to protect them from corrosion caused by the food products contained inside.

b. General characteristics of aluminum cans 

• Aluminum cans are generally two-piece cans, consisting of a body integrated with the bottom and a separate lid.
• They are particularly suitable for carbonated soft drinks and beer, which are liquid products that generate internal pressure. Without sufficient structural strength, cans can easily deform or become damaged by mechanical impacts.
• Aluminum packaging is lightweight, making transportation more convenient.
• Cans have different thicknesses in different areas: the bottom is the thickest, the cylindrical body becomes progressively thinner toward the middle, and the neck and joining area are thicker than the central body.
• Aluminum cans provide protection against ultraviolet rays.

3. The impact of can characteristics on cleaning 

• For two-piece cans, especially lightweight aluminum cans, the material is relatively thin and can easily be scratched, punctured, or deformed during the cleaning process.
• High heat resistance: As metal packaging, cans are highly resistant to heat and can be sterilized using hot steam at approximately 90–100°C without affecting their structure.
• Limited resistance to chemical cleaning solutions: Metal materials can readily react with chemical cleaning solutions. During cleaning, highly concentrated solutions may cause chemical corrosion. For cans made from materials that are highly reactive to chemicals, it is best to use only water for cleaning and sterilization.