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Test for Glass Containers: The Quality Control of the Packaging Material

When it comes to storing your food, beverages, or pharmaceutical products, glass containers are a popular choice for their clarity, chemical inertness, and overall safety. You might appreciate glass for its aesthetic appeal or how it maintains the integrity of what’s inside without imparting flavors or harmful chemicals. However, it’s not just about looks or taste; the quality and durability of glass containers are critical, especially when they’re used to store pharmaceutical products. This is where specific tests for glass containers come into play, ensuring that every jar, bottle, or vial meets rigorous standards before they ever reach your hands.

Testing glass containers involves a series of procedures to assess their suitability and resistance to the stresses they will face during their lifespan. This article will discuss various tests that are commonly performed on glass containers at different stages.

Types and Uses of Glass Containers

A wooden shelf stocked with several glass jars containing dry food ingredients. The jars have metal clamp lids, ensuring an airtight seal for freshness. Visible contents include rice, pasta, legumes, and spices, highlighting the use of glass jars for pantry organization and food preservation

Glass containers come in many forms, including bottles and jars, all designed with a specific application in mind. Your choice might range from small vials for pharmaceuticals to large water bottles. 

There are several types of glass used for packaging, which have different properties and applications. The main types are:

  • Type I borosilicate glass: Has high heat resistance and chemical durability. Used for pharmaceutical packaging and laboratory glassware.
  • Type II treated soda-lime glass: Type II glass is treated with sulfur for increased chemical resistance. Used for parenteral and non-parenteral pharmaceutical products.
  • Type III regular soda-lime glass: The most common and inexpensive type of glass. Used for food, beverages, cosmetics, and solid oral dosage pharmaceuticals.
  • Amber glass: Tinted soda-lime glass that protects contents from UV light. Used for light-sensitive products like beer or medication.
  • Lead crystal glass: Contains lead oxide, used decoratively for perfume bottles and some spirits.

Testing Methods and Procedures

A laboratory setting with a collection of glassware containing liquids in various vibrant colors.

In the world of glass container manufacturing, testing and quality control are paramount. Precise standards guide these tests to ensure safety and performance.

Understanding ASTM C147 and Test Method A/B

ASTM C147 provides standard test methods to determine the internal pressure strength of glass bottles, vials, ampoules and other containers. It involves gradually increasing internal hydraulic or pneumatic pressure until container failure.

About ASTM, two test methods are described – Method A applies a pre-set pressure level whereas Method B ramps pressure at a steady rate until bursting occurs. The maximum pressure withstood is noted as the failure pressure.

  • Test Method A: In this test, a sample of glass is subjected to a dilute acid solution, and the amount of glass dissolved is measured using SI units, indicating the material’s durability and resistance to acidic contents.
  • Test Method B: It involves using a buffer solution to maintain a specific pH, where the performance of the glass is evaluated under tightly controlled conditions, highlighting its resilience to chemical stress.

The measured failure pressure is compared to specified limits based on container dimensions, capacity, and end-use. Key aspects evaluated are pressure resistance and mode of fracture to ensure adequate safety margins.

Factors like glass thickness, defects, thermal history, and loading rate impact outcomes. The test verifies the container’s capability to withstand internal pressures during processing, shelf life, and transportation without fragmentation hazards.

 Solubility Test 

The solubility test is an important analytical procedure performed on the glass to determine its chemical durability and resistance to alkali leaching when in contact with water or aqueous solutions.

In this test, a piece of glass is immersed in distilled water or dilute acid, and the solution is then evaluated to determine the amount of glass that has dissolved into the liquid.

The test aims to provide an indication of the hydrolytic resistance and chemical stability of a glass material under extreme conditions. The results serve as a quality control check to ensure compliance with specifications and suitability for the intended pharmaceutical or other application.

Key factors that impact the test outcome include glass composition, thermal history, surface condition, and test parameters like temperature, duration, and water volume. Allowable limits vary based on glass type as per pharmacopeial monographs.

Thermal Shock Resistance Testing

Thermal shock resistance testing determines the ability of materials and components to withstand sudden extreme temperature changes without cracking, fracturing or undergoing physical damage.

In this test method, test specimens are subjected to rapid thermal transitions like immediate transfers between hot and cold environments or abrupt temperature changes in the surrounding medium.

Typical temperature extremes range from -70°C to +150°C.

Key aspects assessed are structural integrity after thermal shock exposure, absence of cracks/fractures, and maintenance of functional performance. The test aims to simulate real temperature fluctuations seen in practice due to factors like rapid weather changes, equipment startup/shutdown, or operational thermal cycles.

Vertical Load Test:

The vertical load test, also known as the axial load test, is a key quality control test performed to determine the mechanical strength and ability of glass containers to resist vertical forces during handling and storage.

In this test, containers are subjected to gradually increasing compressive load applied vertically through flat plates until failure occurs. The load level causing failure is noted to compare against specified limits. The test can also be carried out to a pre-set load level for pass/fail evaluation.

Key aspects assessed are the maximum load withstood before fracture or an acceptable degree of deformation. The test simulates stress conditions encountered in practice and verifies sufficient strength margins and compliance to safety codes.
Factors like glass thickness, capacity, geometry, defects, and vertical force application rate influence the test outcome. Specifications for minimum strength vary as per container type and intended application.

Internal Pressure Strength Test

Internal pressure strength testing determines the ability of glass bottles and jars to resist fracture when subjected to expected internal pressures during processing and shelf life.

In this test method as per ASTM C147, glass containers are securely sealed and gradually pressurized internally either at a steady rate (Method B) or held at a pre-set pressure level (Method A) until bursting occurs. The pressure level causing failure is recorded.

Key aspects evaluated are the maximum inner surface pressure withstood and the mode of fracture. The measured burst pressure is compared with specified limits based on container dimensions, capacity, and expected product pressures. The test simulates realistic pressure conditions that packaged foods, beverages, cosmetics, and pharmaceuticals can exert over time due to factors like gas release, temperature changes, etc. It serves as a critical quality control check before container sealing and distribution. 

The pressure strength is influenced by glass thickness, defects, composition, thermal history and loading rate. Enhanced safety margins prevent explosions and fragmentation hazards. 

Water Vapour Permeability Test

The water vapour permeability test is used to measure the rate and amount of water vapour that can pass through a material over time. It indicates how breathable a material is.

In this test method, a circular specimen is securely clamped over an open test vessel containing a desiccant or water. The vessel is placed in a controlled atmosphere with a set humidity and temperature. Air is circulated over the surface of the specimen at a specified velocity.

Over a measured duration, the mass of water vapour that permeates through the specimen into the vessel is quantified by periodic weighings. This allows the calculation of the water vapour transmission rate and permeability of the test material.

Key parameters that are controlled include air temperature, relative humidity levels on each side of the specimen, and the air circulation rate. The permeability result can vary significantly depending on these test conditions.

The test has applications in evaluating materials used for packaging, clothing, footwear, gloves, and protective equipment, among others. It indicates the ability of materials to allow perspiration and moisture vapour to dissipate through them.

Fragmentation Test

The glass fragmentation test is a quality control test performed on tempered or thermally strengthened glass to determine the level of residual stress and safety of the glass. In this destructive test, a tempered glass specimen is fractured and the resulting glass fragments are analyzed. Key aspects assessed are the number of fragments counted in a test area, size distribution of fragments, and fragmentation pattern.

Standards like EN 12150-1 define the minimum fragment count requirements based on glass thickness for safety glass classification. A higher fragment count indicates greater residual compressive stress on the glass surface, resulting in enhanced safety through a higher degree of fragmentation.

The test provides a practical and reliable means to ensure proper tempering, measure residual surface compression, and meet safety codes. However, it does necessitate breaking glass samples and manually counting fragments, which is tedious. Emerging digital analysis techniques are automating the quantification process for improved efficiency.

Specific Testing for Food and Beverage Containers

When it comes to food and beverage containers, specific tests are tailored to address concerns unique to these applications. Glass food storage containers must pass stringent tests to ensure they do not contaminate the food or alter its taste. These may include sensory evaluations and seal integrity checks.

  • Spectral Transmission test:

Spectral transmission testing measures the amount of light transmitted through glass at different wavelengths across the ultraviolet, visible, and infrared regions.

It involves using a spectrophotometer to quantify glass transmission percentage or transmittance from 290-450 nm range for pharmaceutical containers and from 250-1800 nm for other glass products. 

Key aspects assessed are the effect of glass composition, thickness, defects and curvature on transmittance. The test aims to ensure adequate UV blocking for product protection, appropriate visibility, and compliance to industry specifications.

Advanced Testing Techniques

The glasses are set on a white linen tablecloth, which suggests a formal or fine dining setting. In the background, there is a folded white napkin with a set of cutlery on top of it, consisting of a fork and a knife, which are aligned parallel to each other.

In order to ensure the safety and quality of glass containers, advanced testing techniques are crucial. These techniques help you determine the durability and resistance of glass to various stresses, ensuring they pass critical safety tests.

Hydrolytic Resistance Using Autoclave Methods

When you’re testing for hydrolytic resistance, autoclave methods are integral. These methods involve exposing the glass to steam under pressure, simulating accelerated aging conditions. Testing can follow procedures such as Test Method B-A (also known as autoclave test method A), which helps you assess the resistance of the glass when it is subjected to an aggressive, moist environment at elevated temperatures.

  • Hydrolytic Autoclave Test: A sample of the glass is powdered, then exposed to steam in an autoclave. The durability of the glass is assessed by measuring the amount of alkali released.

Additionally, there’s Test Method B-W and Test Method P-W, both of which take into account the weight loss of the glass sample after undergoing the autoclave process. The data gleaned from these tests is essential for you as a glass manufacturer to gauge the performance of glass containers under conditions that mimic actual use.

Analyzing Failure and Performance Under Stress

Analyzing why glass fails and measuring its performance under stress are tests designed for your long-term benefit. These progressive tests help you pinpoint underlying issues that could lead to product failure.

  • Failure Analysis: A methodical approach where the glass is examined post-failure to identify the cause. Techniques such as fracture analysis and surface inspection are used. This data is invaluable in preventing future failures.
  • Durability Test: It evaluates how well glass containers can withstand mechanical stress. Containers are subjected to conditions mimicking real-world handling and usage to assess their strength and durability. This test helps assure that glass containers pass the test of everyday use without failure.

Pharmaceutical Packaging Testing

The Powdered Glass Test

The Powdered Glass Test is a quality control test performed on glass containers used for pharmaceutical packaging to estimate the amount of alkali that can leach out from the glass surface under extreme conditions.It involves the following key steps:

  • Glass containers are crushed into a fine powder to increase the surface area exposed to the testing conditions.
  • The powdered glass sample is washed thoroughly to remove any adhering fine particles.
  • The sample is then heated in water at 121°C in an autoclave for 30 minutes. This temperature accelerates the leaching process.
  • The solution is then titrated with sulfuric acid using a methyl red indicator to determine the amount of alkali leached.

The test provides an indication of the hydrolytic resistance and chemical durability of a glass container. Allowable limits are set as per pharmacopeial specifications based on the type of glass. A higher amount of leached alkali indicates poorer resistance and increased risk of product interaction.

The Water Attack Test

The Water Attack Test is used to determine whether the alkali resistance of glass containers can be intended for pharmaceutical use, especially those treated with sulfur dioxide.

In this test, entire glass containers are immersed for 30 minutes along with water in an autoclave at 121°C. Under these harsh conditions, alkali from the glass surface leaches out into the water.

The test solution is then titrated with a standardized acid solution to quantify the amount of alkali (usually sodium ions) released. The leaching of alkali is then calculated and compared to the allowable pharmacopeial limit based on the type of glass.

This test provides an exaggerated indication of the hydrolytic resistance and chemical durability of the glass containers. A higher amount of the leakage of alkali indicates poorer alkali resistance and an increased risk of product interaction between the glass and the pharmaceutical contents over the shelf life.

Physical and Performance Testing

The image displays a close-up view of several amber glass medication bottles with child-resistant caps, alongside a variety of pills and capsules.

When considering the reliability and safety of glass containers, physical and performance testing are fundamental. You’ll want to focus on how well the containers can handle pressure and ensure their sealing properties are up to standards.

Pressure and Load Resistance Examination

Testing for internal pressure strength is critical to determine if your glass containers can withstand the pressures they will encounter, especially if they are intended for carbonated beverages or other pressurized contents. A progressive test method might be used, where pressure is incrementally increased on the container until it reaches the failure point. For accurate and repeatable results, it’s vital that the equipment used is well-calibrated and regularly maintained.

  • Test Methods: Common tests include the burst test and the pressure test, which assess the glass to ensure it’s robust enough to avoid breakages during normal use and capable of handling sudden changes in pressure.
  • Specimen Size: Each container tested should be a representative sample of your production run to ensure consistency.

Evaluating Container Sealing Properties

You must also examine the sealing properties of your containers to make sure they’re both airtight and leakproof. This involves testing the container with its intended closure under conditions that it might face during its lifecycle, such as being stored in a refrigerator or heated in a microwave. A container’s lid or closure mechanism should be repeatedly tested to ensure the seal remains intact and functional.

Sealing integrity and leak testing

Sealing integrity and leak testing of glass containers are vital to ensure airtight closure and prevent microbial contamination in sterile healthcare products. Common test methods include vacuum decay, bubble emission, and dye ingress tests. The containers are filled with a solution, sealed, and checked for any leaks indicated by solution loss over time, gas bubbles, or entry of exterior dye solution.

Regulatory and Standard Compliance

International vs National Standards Comparison

As you navigate through the regulations, you’ll encounter both international and national standards. International standards like those set by ASTM (American Society for Testing and Materials) provide a consensus on specifications concerning material quality, safety, and environmental considerations. These standards serve as a benchmark across different countries and help in creating a common ground for safe packaging.

On the other hand, national standards tend to address specific regulatory limitations and safety concerns that are particular to a country. These standards might be more stringent or detailed in certain aspects when compared to international standards to ensure compliance with local policies and practices.

Safety and Environmental Considerations

Environmental practices weigh heavily in the compliance process. You are required to ensure that your glass packaging adheres to environmentally safe production and disposal processes. Regulatory limitations can also extend to the environmental impact of the materials used and the manufacturing process of glass containers. 

In summary, rigorous testing is essential to ensure the safety and integrity of glass containers used for food and beverage products. The tests described evaluate key attributes like strength, durability and hermetic sealing ability that are critical to prevent breakage during production, transportation and usage. By adhering to standards and conducting regular assessments, manufacturers can have confidence their glass packaging will protect contents and perform as intended. As new container designs and materials emerge, testing will continue to play an important role in quality control and maintaining consumer trust in the glass packaging industry. Adapting test methods to innovations helps support sustainable growth while prioritizing safety.

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