Standard: TAPPI
Method: T 425
Title: Opacity of paper (15/d geometry, illuminant A/2°, 89% reflectance backing and paper backing)
Overview
Opacity is a fundamental optical property of paper and is determined by a ratio of reflectance measurements. The opacity of the sheet is influenced by thickness, the amount and kind of filler, degree of bleaching of the fibers, and coating. This method can be used to obtain two different opacity values: TAPPI Opacity (or opacity using 89% reflectance backing) is the ratio of reflectance of a sample when backed with a black body to the reflectance of the sample when backed with a white body with a known reflectance of 89%. Printing Opacity (or opacity using a paper backing) is the ratio of the reflectance of a sample when backed with a black body to the reflectance of the sample when backed by multiple sheets of paper.
Samples
To ensure proper sampling for opacity testing it is recommended that ten, 8.5” x 11” sheets of paper are submitted for testing. If sample availability is limited, the testing can be performed on the amount of sample available.
IPS can measure and report both TAPPI and printing opacity. Please indicate which opacity measurement you require. If the type of opacity is not indicated, IPS will perform TAPPI opacity testing. IPS can also perform ISO opacity using TAPPI T 519.
Please note: IPS cannot sell or otherwise provide standards, specifications, or test procedures to third parties.