Brightness of paper

Protocols of use First register the image brightness of paper matrixes in plates (plate 1) then again register the second image of the plate with biotests (plate 2) (see suppl. 3). The value of D was calculated by the standard formula ... 

Brightness Meter. A special type of reflection meter for evaluating the brightness of paper and similar products by measuring the diffuse... 

TAPPI Standard Method A-452m-58, Brightness of Paper and Paper-... 

OBAs, also called FWAs, represent 3% by value and only 1% of the total dry amount of specialty chemicals (see Fig. 3.2 and 3.3). They increase the whiteness/ brightness of paper and are preferably added to the stock. They are very effective when used with highly bleached pulps, and much less effective, or even ineffective, when appHed to unbleached chemical pulps and mechanical pulps. OBA are also used in surface applications such as surface sizing and paper coatings. 

Optical Properties. Brightness, or visual whiteness of paper, can be defined as the degree to which light is reflected uniformly over the visible spectmm. Since pulp and typical impurities tend to be yellowish, blue dye is sometimes added in addition to appropriate fillers. The percentage reflectance is usually measured in the blue end of the spectmm at or near 457 nm (14). 

Chemical, semichemical, or mechanical breakdown of pulping material into fibers Removal of pulp impurities, cleaning and thickening of pulp fiber mixture Addition of chemicals in a staged process of reaction and washing increases whiteness and brightness of pulp, if necessary At nonintegrated pulp mills, pulp is dried and bundled into bales for transport to a paper mill... 

In order to adjust the dark-field illumination, project the illumination light onto a piece of paper placed on the microscopic stage or on the obj ective lens. Adjust the position of the slit and the height of condenser so that the transmission light illuminates the sample uniformly and brightly, and that the diameter of the shaded area produced on the surface of the objective lens is larger than that of the objective lens (see Fig 1C). 

The effect of color production from carbohydrate transformation in an alkaline pulping process, such as kraft pulping, is illustrated in Table III. Cotton linters, which originally had a brightness of 90.5%, were treated for 4 h at 180° with kraft liquor, with and without additives. Brightness was measured on paper made from the resulting, washed pulp. 

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