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TAPPI T 646 Mineral pigment brightness

Standard:

TAPPI

Method:

TAPPI T 646

Title:

Brightness of clay and other mineral pigments (45/0)

Scope

TAPPI T 646 Mineral pigment brightness describes a procedure for determining the brightness of clay or other mineral pigment that has been pulverized under controlled conditions and made into a uniformly compacted pigment plaque. This method is for use with minerals normally used in the manufacture of paper and is not intended for highly colored pigments.

The instrument employed has the same spectral, geometric, and photometric characteristics as that described in TAPPI T 452 “Brightness of Pulp, Paper, and Paperboard (Directional Reflectance at 457 nm).” The brightness scale applicable to this method is the same as the brightness scale described in TAPPI T 452.

Summary

This method provides: (a) a scale for the measurement of the brightness of clay and mineral pigments using 45/0 geometry, (b) a method for verifying the calibration of each instrument used for brightness testing, (c) procedures for the preparation of specimens from both dry powder or aqueous slurry including procedural variations for several specific clays and mineral pigments.

Significance

The brightness of clay or mineral pigment affects the brightness of the paper with which it is used. Although one might assume that the measured brightness is a property of the material, in fact the value obtained depends significantly on the manner of specimen preparation. For this reason, specific instructions for drying and pulverizing the material and for pressing the test plaque are detailed in this method.

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IPS cannot sell or otherwise provide standards, specifications, or test procedures to third parties.