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Participants will determine opacity in accordance with TAPPI T425 and using 15 degree/diffuse geometry, illuminant A/2 degree instruments, and 89% reflectance backing.

Sample Description: Two similar samples, each containing ten pre-conditioned 4.25" by 5.5" sheets of printing paper. Samples are selected from a variety of papers within the opacity range.

Samples ship every other month for a total of six shipments beginning with the earliest available cycle of testing. Testing is conducted during January, March, May, July, September, and November, with samples for each test cycle shipping in the month prior.

This test is included on CTS' Scope of Accreditation to ISO/IEC 17043.