This practice is useful as a screening basis for acceptance or rejection of transparencies during manufacturing so that units with identifiable flaws will not be carried to final inspection for rejection at that time.

This practice may also be employed as a go-no go technique for acceptance or rejection of the finished product.

This practice is simple, inexpensive, and effective. Flaws identified by this practice, as with other optical methods, are limited to those which produce temperature gradients when electrically powered. Any other type of flaw, such as minor scratches parallel to the direction of electrical flow, are not detectable.

If another method (equally suitable for flaw detection) is designated for final optical inspection of the laminated part under power, the polarized light practice will not be required for the final inspection.

1.1 This practice covers a standard procedure for detecting flaws in the conductive coating (heater element) by the observation of polarized light patterns.

1.2 This practice applies to coatings on surfaces of monolithic transparencies as well as to coatings imbedded in laminated structures.

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

1.4 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 and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements see Section 6.