ASTM C1956-25

1.1 This test method covers a laboratory screening procedure for determining the compatibility of laminated glass edges with elastomeric glazing sealants and glazing tapes after exposure to heat, humidity, and ultraviolet light.

1.2 This test method is applicable to all types of single or multilayer laminated glazing including but not limited to those containing ethylene vinyl acetate (EVA), ionomer, aliphatic polyurethane (TPU), polyvinyl butyral (PVB) interlayers and glass, and plastic glazing configurations.

1.3 This test method requires the sealant and glazing tape to be in intimate contact with the edge of the laminated glass having the most direct access to the interlayer throughout the test duration.

1.4 This test method does not include assessment of the sealant or glazing tape itself or the sustainability of sealant properties through the exposure.

1.5 This test method includes the observation of two parameters as follows:

1.6 This test method may be conducted in accelerated exposure or natural exposure, or both, according to the procedures outlined.

1.7 This test method is applicable for any liquid sealant, one or more parts, which can be tooled into intimate contact with the laminate edge.

1.8 This test method is applicable to glazing tapes that are capable of achieving and maintaining intimate contact with the laminate edge throughout the test duration.

1.9 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

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 In most installations where the glass is mechanically captured within a framing system, the sealant is used as a weather seal and rarely comes into contact with the laminated glass edge. However, in these installations where a heel or toe bead is applied, the sealant could come into contact with the edge of the laminated glass and potentially with the interlayer. In butt joint glazing, structurally glazed, and some point fixed glazing systems where sealants are used as the primary weather seal, contact will occur with the edge of the laminated glass and interlayer. Reactions between the sealant, glazing tapes, and interlayer are possible and could cause a visual anomaly. This test method purports to outline a standardized test method to evaluate the formation and severity of such visual edge effects.

5.2 Sealants and tapes are tested for compatibility when applied to the laminate edge, in direct contact with the interlayer and then exposed to specified exposure conditions. The data should be used for comparative evaluations only. Extrapolation to in-field applications cannot be guaranteed and thus a rating of compatible or non-compatible cannot be given to the samples based on this data alone. The user is cautioned to use this data as guidance only and not a guarantee of performance.