ASTM G229-26

1.1 This practice covers a procedure for determining the time of wetness for a location used in the outdoor exposure of materials.

1.2 This practice covers a procedure for determining the total time of wetness due to condensation and rainfall.

1.3 This practice does not distinguish the individual causes of time of wetness such as condensation and rainfall.

1.4 This practice does not address total or actual amount of time that a specific specimen is wet. This practice is intended to provide direction on how to estimate a general wetness value for a location.

1.5 This practice does not account for differences in mounting and exposure of the test specimen.

1.6 This practice can be used to characterize and compare different locations based on that location’s ability to create surface moisture on an exposed test specimen through condensation and rainfall.

1.7 Only one technique for estimating potential time of wetness is covered in this practice. Other methods exist for determining time of wetness are covered in other standards such as Practice G84.

1.8 This practice covers an apparatus that can be built by most people using readily available parts from various retail stores. Other methods use commercially produced apparatus that are self-contained, such as leaf-wetness sensors. There are also several mathematical methods that derive wet time from published weather data, and require no additional specialized instrumentation. One example is ISO 9223. Appendix X1 contains more information on these other methods.

1.9 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.

1.10 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.11 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.1 Time of wetness is one of most important parameters in weathering. The presence or absence of water may affect the rate and type of degradation. The presence or lack of water does not matter for some materials.

5.2 Testing locations can be categorized by their time of wetness. The total time of wetness can be related to the amount and type of weathering that is achieved.

5.3 There are several ways to measure rainfall amount and duration, but not for condensation. In some climate zones, condensation can be considered as the most important factor contributing to surface wetness.

5.4 The purpose of this practice is to permit the estimation of the time of wetness at a particular location for the intent of characterizing that site. The actual time of wetness of any particular surface, or a specific specimen on exposure requires the use of a different technique such as that described in Practice G84.

5.5 This technique cannot be used to directly measure the time of wetness of any specific specimen.

5.6 The wick shall be mounted to a non-conducting substrate such as glass. Based on historical data, glass is the preferred substrate. Other non-conducting materials such as rubber, plastic, and wood, may be used but will not yield the same results as glass. The substrate shall be indicated in the test report.

5.7 This technique was first developed and verified c1931 by Charles F. Kettering4.