5.1 Light penetration may be used to control the quality of many RECPs. Light penetration has not been proven to relate to field performance for all materials.

5.2 The light penetration of RECPs may vary considerably, depending on the composite materials used in the matrix of the mat or due to inconsistency within a given mat. To minimize variation, specific sample size and procedures are indicated in this test method to help ensure comparable results.

5.3 This test method may be used to determine the effect of different composite materials and makeup of RECPs on the penetration of light.

5.4 This test method may be used for acceptance testing of commercial shipments of RECPs. Comparative tests as directed in 5.4.1 may be advisable.

5.4.1 In case of a dispute arising from differences in reported test results when using this test method for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. At a minimum, the two parties should take a group of test specimens that are as homogeneous as possible and that are formed from a lot of material of the type in question. The test specimens should be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using Student's t-test for unpaired data and an acceptable probability level chosen by the two begun. If bias is found, either its cause must be corrected, or the purchaser and supplier must agree upon the known bias.

Note 1: The light penetration has no definitive relationship to the amount of ground cover provided by a RECP, as the amount of light penetration may include light passing through translucent elements or light deflecting off of elements of the RECP structure. Thus, this test method is not intended to be used to determine a percent ground cover value for RECPs.

Note 2: The user should be aware that the makeup and possible movement of the composite materials, and the like, may affect the RECPs following the time when they are rolled up on rolls, shipped, and stored.