What is bloom on glass containers?

Glass is often used in the packaging industry to provide an eco-friendly option that also feels premium and attractive to consumers. A few problems can occur in glass production, with glass bloom or glass weathering being a common technical issue.

When using glass as a packing material, it’s important to understand what glass bloom is, what causes it, and how it can be prevented. We’ll look at this in more detail in this guide.

What is glass bloom?

Bloom on glass, also known as glass weathering, is a condition in which a whitish, hazy film appears on the surface of glass containers. This bloom can affect the aesthetic appeal and perceived quality of the glass, making it a significant concern for manufacturers and businesses looking to use glass packaging.

What causes glass bloom or glass weathering?

Glass bloom is primarily caused by the reaction of the glass surface with moisture and environmental factors. In storage, glass can be subject to condensation which forms when the temperature drops – this can occur simply as the daily temperature cycles from day to night. This can also happen during transportation too.

Condensation leaches out the alkali ions (sodium or potassium) from the glass which leads to the formation of an alkaline solution. As the temperature rises again and the liquid evaporates from the surface of the glass, it leaves a concentrated alkali solution behind. These alkaline salts are left on the surface of the glass once the liquid has completely evaporated.

Here are some common causes:

• Alkali leaching: prolonged exposure to moisture can cause alkali metals in the glass to leach out, leaving behind a white, powdery residue.
• Environmental pollutants: airborne pollutants such as sulphur dioxide and nitrogen oxides can react with the glass surface, contributing to weathering of glass.

The effect of glass bloom

Glass bloom can have adverse effects such as:

Aesthetic impact

The cloudy, hazy appearance of bloom can detract from the visual appeal of glass containers, making them look dirty or damaged which is not ideal when using them as packaging.

Product perception

Consumers may see glass containers as lower quality, which can affect brand reputation and sales.

Structural integrity

In severe cases, prolonged weathering can weaken the glass container, compromising its structural integrity.

How do you prevent glass bloom?

Preventing glass bloom involves understanding its causes and taking measures to prevent them. Glass bloom usually happens during storage or transportation after the containers have been packaged. Here are some of the measures you can take to prevent glass bloom:

1. Proper storage

Glass containers should always be stored in a dry environment with controlled humidity levels to prevent moisture from reacting with the surface of the glass. In addition, ventilation should be provided to minimise condensation and reduce the risk of bloom.

2. Surface treatments

Protective coatings can be applied to the surface of the glass to provide a barrier against moisture and any environmental pollutants. Chemical treatments can also be used to alter the surface of the glass and make it less reactive to environmental factors that can cause bloom.

3. Cleaning and maintenance

Cleaning glass containers regularly with the right cleaning agents can help to remove build-up of salts or pollutants. Routine inspections are also recommended so that signs of bloom can be picked up and addressed before they become worse.

4. Material considerations

Another way to prevent bloom is to use glass formulations with low alkali content which can reduce susceptibility to bloom and weathering. Plus, quality control during the manufacturing process will ensure consistent glass composition and surface quality to reduce the risk of bloom occurring.

Overall, the ideal storage conditions for glass containers are dry, well ventilated areas with a relatively constant temperature and low humidity. The way the glass is manufactured and checked throughout its production can also contribute to bloom and weathering.

How Glass Technology Services can help

Glass bloom, or weathering, is a common issue affecting the appearance and quality of glass containers. By understanding the causes and implementing preventative measures, the integrity and aesthetic appeal of glass products can be maintained.

As an independent test house and consultancy for the global glass supply chain, Glass Technology Services helps to resolve production problems, verify the quality of glass packaging and containers and develop innovative glass applications.

Our technical glass experts offer a comprehensive glass defects and contamination analysis service.

We analyse the composition of glass products and causes of defects in the manufacturing process so we can resolve production issues quickly. We examine surface contamination, delamination, misting and bloom.

If you have a question about our services or want more information about how we can help your business, please contact our team. We’d be happy to answer your questions.