ASTM C149 Test for Thermal Shock Resistance of Glass Containers

Scope:

ASTM C149 determines the relative thermal shock resistance of commercial glass containers that have to withstand sudden changes in temperature during application in services such as washing, pasteurization, or when glass is transferred from a warm to a colder medium or vice versa.

The test apparatus consists essentially of a basket for holding the glassware upright, a hot water tank, a cold water tank, and a timed means for immersing and transferring the basket from the hot to the cold bath. Indicating controllers or dial thermometers are used to maintain the temperatures of the baths. Test procedures include pass tests, progressive tests to a predetermined percent of breakage, total progressive tests, and high-level tests.

Test Procedure: 

For ASTM C149 testing, the temperature of the cold bath is adjusted to 21°C  and the temperature of the hot bath is adjusted to a temperature differential (usually 42°C for the first immersion). The temperature differential is the difference in temperature between the hot bath and the cold bath. 

Empty glass bottles are placed in a basket. When the temperature of the baths reaches the determined value, the basket is immersed in the hot bath. The glass bottles get filled with hot water. They are allowed to sit there for 5 minutes and then they are transferred to the cold bath. They are allowed to sit in the cold bath for 30s and then they are removed. Each individual container is inspected to determine the number of containers failing.

Different test procedures are used in ASTM C149 depending on the purpose of the test.

1. Pass Test: In this test, the temperature differential between the hot bath and the cold bath is predetermined and fixed. Glass Containers may or may not break. Pass test is used for the routine testing of samples from continuous production in a manufacturing plant.

2. Progressive Test (fraction): The temperature differential is increased by uniform increments by raising the temperature of the hot water bath until a predetermined percent of glass containers break. 

3. Progressive Test (Total): This test is continued until all the containers break. 

4. High-Level Test: The temperature differential is predetermined to be high enough to break all the glass containers.  

Specimen Size: 

The following specimen sizes are defined in ASTM C149 for each test method:

• Pass Test: 50 containers, randomly selected, but representative of the mold cavities, are tested as the first sample in a double sampling method, followed, when necessary, by the second sample of 50 containers equally random and representative. 
• Progressive Test: A single sample of 50 containers is employed. 

Data: 

The following information is reported in ASTM C149: 

• The method of sampling. 
• The number of containers from each mold included in the sample. 
• Time of transfer used. 
• Results of test employed. 

For the pass test, the following are reported: (1) temperature differential used, and (2) number of containers that failed the test.

For the progressive test (fraction): (1) differential at which the first failure occurred and the number of containers that failed at that differential, and (2) differential at which a predetermined percent of the sample broke. 

For the progressive test (total): (1) differentials used during the test and number of containers that failed at each differential, and (2) average differential of failure.  

For the high-level test: (1) differential used in the test, and (2) number of containers that failed at that differential.

Conclusion:

ASTM C149 determines the relative Thermal Shock Resistance of any commercial Glass Container (bottles and jars) that has to withstand sudden changes in temperature (thermal shock) while in use.