Overview
EN ISO 7459:2004 (ISO 7459:2004) specifies standardized test methods to determine the thermal shock resistance and thermal shock endurance of glass containers (bottles, jars). Published by CEN in collaboration with ISO TC 63, the standard defines how to expose containers to sudden temperature changes and record failures so manufacturers and quality labs can quantify performance and compare products consistently. It does not apply to laboratory glassware (see ISO 718).
Key topics and technical requirements
- Terms and definitions: container, thermal shock, thermal shock resistance (°C the container withstands without breaking), thermal shock endurance (temperature difference at which ~50% fail).
- Apparatus:
- Cold water bath and hot water bath, each sized to at least 8 dm³ of water per kilogram of glass tested, with circulation and thermostatic control to ±1 °C.
- A basket made from inert material to hold containers upright and prevent floating; may be used with automatic transfer equipment.
- Procedure essentials:
- Heat immersion: containers are filled and immersed in the hot bath for at least 5 minutes.
- Transfer: basket moved from hot to cold bath within a maximum of 16 s.
- Cold immersion: containers kept in cold bath for 30 s, then inspected for cracks or breakage.
- Baths must have sufficient depth to fully immerse containers plus at least 50 mm.
- Test types:
- Pass test: single thermal shock at agreed temperature difference (t1 − t2).
- Progressive test: repeat tests with increasing temperature differences (commonly in 5 °C increments) until a specified percentage of breakages occurs.
- Total progressive test: continue until all containers fail; if hot bath reaches 95 °C, lower cold bath temperature to continue.
- High-level test: single test at a high ΔT to cause an agreed failure percentage.
- Thermal shock endurance: determined from a graph of cumulative failure percentage vs. temperature difference; the interpolated ΔT at 50% failure is reported.
- Safety and reporting: laboratory safety precautions are required. Test reports must reference the standard and include sample size, bath temperatures, failure counts per ΔT, date, location, and responsible signature.
Applications and users
- Used by glass container manufacturers, quality control laboratories, packaging engineers, and product development teams to:
- Validate container durability against rapid temperature changes (filling, cooling, processing).
- Compare formulations, annealing processes, or design variants.
- Set product specifications and supplier acceptance criteria.
- Relevant for industries packaging food, beverages, chemicals, and any application where containers see rapid thermal transitions.
Related standards
- EN ISO 7458 - Internal pressure resistance (glass containers)
- EN ISO 8113 - Resistance to vertical load
- ISO 718 - Laboratory glassware - Thermal shock (not covered by EN ISO 7459)
- Other glass container test-method standards referenced in the EN ISO series
Keywords: EN ISO 7459:2004, ISO 7459:2004, glass containers, thermal shock resistance, thermal shock endurance, test methods, hot water bath, cold water bath, packaging testing.