3.1 This practice describes procedures to use in determining the effects of an open-flame carbon-arc light source, an enclosed carbon-arc light source, a xenon-arc light source, or a fluorescent UV source along with heat and moisture on rubber specimens held in a jig or holder with or without a specified strain. The purpose is to attempt to accelerate the effects produced by light, heat, and moisture in the natural environment. Exposures are not intended to simulate the deterioration caused by localized weather phenomena, such as atmospheric pollution, biological attack, and saltwater exposure. The Significance and Use section in Practice G151 and the standard for the appropriate apparatus, that is, Practices G152, G153, G154, or G155 should be consulted for additional information on significance and use of the exposure tests.

3.2 The primary criterion used in estimating resistance to weathering is the percentage decrease in tensile strength and in elongation at break. A supplementary criterion for estimating resistance to weathering is the observed extent of surface crazing and cracking.

3.3 Results obtained by use of these test procedures should not be represented as equivalent to those of any natural exposure test until the degree of quantitative correlation has been established for the material in question.

3.4 Because of differences in the spectral power distributions of the exposure sources as well as the other conditions in the different types of laboratory weathering tests, the different procedures may not result in the same performance rankings or types of failure modes of the materials. Comparisons shall not be made of relative stabilities of materials exposed in different types of apparatus.

3.5 When conducting exposures in devices that use laboratory light sources, it is important to consider how well the artificial weathering conditions will reproduce property changes and failure modes caused by end-use environments on the materials being tested.

3.6 Practices G151, G152, G153, G154, and G155 recommend that a similar material of known performance (a control) be exposed simultaneously with the test specimen to provide a standard for comparative purposes. Preferably, a control material known to have poor durability as well as one that has good durability should be used. The reason for using a control is that reproducibility in ranking stabilities is usually better than reproducibility of absolute changes. Therefore, the use of controls is particularly important when test materials are not being compared with one another.