Hiding power determination

InstmmentaHy, both the hiding power and tinting strength can be determined from the amount of the incident light reflectance of coated white and black substrates. Relationships derived from Kubelka and Munk theory (6) are appHed in actual calculations. 

The choice of parameter used in the determination of size distribution should include consideration of the information needed in the interpretation of the data. For example, in the case of a manufacturer of paint pigment, the size parameter that best describes the hiding power (performance of the pigment) is the projected area of particles. A powdered catalyst manufacturer is primarily concerned with surface-area equivalence. 

DIN 55 987-2-1981 Bestimmung eines Deckvermogenswertes pigmentierter Medien Farb-metrisches Verfahren. ISO 6504-5-1987 (TC 35) Determination of hiding power. Part 5 Colour difference method for dark coloured paints. 

However, there is no exact quantitative method which makes it possible to calculate the critical particle size that will produce an optimum in hiding power in a colored pigment formulation. Although the basic theory behind this phenomenon has been treated extensively, it is still most advantageous for practical R D purposes to experimentally determine the particle size that affords a maximum in hiding power. A more approximate than quantitative rule has been established by H.H. Weber, which makes it possible to estimate the particle size that will afford a maximum in scattering ... 

There are several techniques which determine the hiding power of a pigmented medium for practical application. Colored systems are typically tested by measuring their ability to entirely cover up a standard black and white checkerboard substrate. Parameters used as variables are the pigment concentration and/or the... 

The definition of hiding power is based on a black and white contrasting support upon which the film of coating is applied. The thickness h of the applied film is determined at the point at which the contrasting surface just disappears, as judged... 

Figure 11. Determination of the hiding power of a yellow iron oxide pigment...

The light absorption coefficient of black pigments determines their optical quality. Their color intensity and hiding power depend on the particle size and particle size distribution. The most important black pigments are carbon blacks, iron oxides (Section 3.1.1), and mixed metal oxides (Section 3.1.3). 

Hiding Power. The ability of a paint to obscure underlying color varies with different pigments. The difference between the index of refraction of the vehicle and that of the pigment determines the hiding power. 

Hiding power of pigment in paint can be measured by refiectometry without the use of standard. It is calculated from the determined values of reflectivity and the scattering coefficient. 

The hiding power of the pigmented material is a measure of its ability to hide a colored substrate or differences in the substrate color. The hiding power of the film is determined from the following equation " ... 

Many of the difficulties encountered by these early investigators were related to the insistence of the paint makers that hiding power be determined in "practical" paint systems—that is, that the amount of pigment present be based upon the amount required to produce brushing viscosity in a simple linseed oil vehicle. Since pigments varied in both density and oil absorption, pigment volume concentrations were seldom comparable. The same paint makers also insisted upon a "practical" brush application and preferred visual to instrumental comparisons. 

The authors determined pigment particle size using Green s photographic method (9) which could not have been too precise, but it was claimed that good correlation had been obtained with the relative hiding power values of Hallet (11) when calculated for film thicknesses, providing a residual contrast of 2% over their black substrate (see Table III). 

In the same year (1926) Hallet (16) reappraised his hiding power values and discovered that they could be related to carefully determined tinting strength values by the equation... 

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