Glass fitness for purpose testing

Our extensive fit-for-purpose tests determine whether your glass products are suitable against international, national, industry or in-house standards and specifications. They can also prevent customer complaints and reduce waste.

We complete mechanical and physical performance analysis for products including domestic and trade drinking glasses, bottles, jars and specialist glassware.

Our rigorous tests will determine whether your products are fit for purpose and can perform under the strains they are expected to withstand. We can assess the

• capacity and headspace
• coatings performance
• impact resistance
• internal pressure resistance
• thermal shock resistance
• vertical load resistance

We can also identify faults and failures in photonics and optics components using SEM, EDX and FT-IR analysis (alongside other techniques) to detect issues such as misapplied organics, coating defects and refractive index variances.
 

Capacity and headspace

Capacity and headspace (or vacuity) assessment calculates the volume of liquid held by the container and the volume of remaining space left at the top once filled to the specified level.

This assessment determines whether the correct volume of product can be held whilst still maintaining sufficient headspace/vacuity in order to withstand any changes in pressure that may occur during the product’s lifecycle.

This testing is important to ensure that the container holds the correct amount of product without compromising the headspace, which could lead to product leakage or explosion.
 

Coatings assessment

We determine the longevity of coating performance using our AGR factory line simulator, inducing bottle to bottle abrasion damage at the contact points, then comparing the strength of the virgin and abraded samples. This is particularly useful for returnable glassware.

We measure hot end coatings and finish coatings to determine thickness in ‘coating thickness units’ and make observations about the visual appearance if required. We assess cold end coatings using a slip table to determine the lubricity.
 

Impact resistance

We use pendulum impact testing to determine the impact resistance, strength and breakage characteristics of glass items. This test uses an industry standard, calibrated AGR impactor and is UKAS accredited under ISO 17025.

Impact testing can be undertaken on a range of products, including

• containers and packaging – such as beer bottles and food jars
• trade glassware – such as pint glasses and stemware
• prestige and beauty bottles – such as perfume and cosmetics

Typically, impacts are carried out at the contact point for a particular product, such as the shoulder and heel of bottles or the rim of a pint glass. The testing is carried out until failure of the sample occurs. However, we can test until damage is first visible or at specific impact positions if required.

Our experts can also carry out bespoke impact resistance testing tailored to your specific requirements.
 

Internal pressure resistance

We test the internal pressure resistance of glass bottles used to package carbonated drinks, and those subjected to changes in pressure during their intended use. We fill the glass articles with water and increase the pressure until the point of failure to determine the location of the origin.

Our assessments are made

• with a ramp tester using an accredited test method (UKAS accredited laboratory, No. 1994)
• to the product standard ASTM C147-86 (Standard test methods for internal pressure strength of glass containers)

Internal pressure resistance (also known as burst-pressure, ramp testing or internal pressure strength) is available as a standalone mechanical test, or as part of a quality assessment testing package.
 

Thermal shock resistance

We test the thermal shock resistance of glass that may be subjected to significant differences in temperature during normal use. For example, the shock of taking a casserole dish from a hot oven and placing it on a cool worktop may be enough to cause it to break. The tests involve cycling glass from a hot to cold temperature until it experiences thermal shock failure. This is done to calculate its resistance and the thermal performance of the glass.

Thermal shock tests for glass containers can be provided based on our recommendations, your in-house test methods or to a range of international standards, including

• ASTM C149-86 (Standard test method for thermal shock resistance of glass containers)
• BS EN ISO 7459 (Glass containers. Thermal shock resistance and thermal shock endurance. Test methods)
• BS EN 1183 (Materials and articles in contact with foodstuffs. Test methods for thermal shock and thermal shock endurance)

A thermal up-shock test is also available to assess resistance to shock from cold to hot temperatures – for example, when frozen items packaged in glass are placed directly into a hot oven.

Thermal shock testing is relevant to a wide range of glass products including

• bottles and jars
• cookware and kitchenware
• toiletry and cosmetic containers
• domestic wares, such as bowls, vases, glass drinking vessels, latte glasses and mugs
• cafetieres ('French Press', coffee press, cafetière à piston)
• candle holders, candle jars and hurricane lamps
• technical, industrial and pharmaceutical glasses

Vertical load resistance

We undertake vertical load testing (also known as head load, compression, and axial-load testing) using a compression tester to determine a product’s resistance to vertical load forces.

This is commonly used to assess container glass packaging ­such as bottles, jars and vials – which undergo palletisation, capping or stacking. However, the equipment is also used for assessing flat glass strength for relatively small samples, using 3 or 4-point bend and ring-on-ring testing.

The vertical load strength of glass containers is determined for both pass/fail and progressive (to destruction) testing against the method in BS EN ISO 8113 (Glass containers. Resistance to vertical load. Test method).