ASTM D2805-11 pdf download.Standard Test Method for Hiding Power of Paints by Reflectometry.
4. Summary of Test Method
4.1 The reflectivity R ∞ of the coating is determined from reflectance measurements on black and white hiding power charts.
4.2 The scattering coefficient S of the coating is determined from R ∞ , and the reflectance R 0 and spreading rate H X ofa film applied on black glass.
4.3 The hiding power, H 0.98 of the coating is calculated from the reflectivity R ∞ and the scattering coefficient S. 4.4 As an optional procedure the contrast ratio C at a specified spreading rate H C is calculated from R ∞ and S.
5. Significance and Use
5.1 This is a precise instrumental method giving results having an absolute physical significance without reference to a comparison paint It should he used when maximum precision and minimum subjectisity are required. as in testing specihca’ tion coatings or evaluating the hiding efficiency of pigments
5.2 Hiding power Test Method [)344 is visual instead of instrumental, and gives results that are relative to a material standard instead 411 absolute. It is less precise than Test Method 1)2805 but mote closely aligned with practical painting proceitures.
6. Apparatus and Materials
6.1 .Suhonjfr.c:
6.1.1 BlotS Glass Panels, minimum size 200 by 200 mm. and appnisimately b’mm thick.
61.2 BlotS and While Paper (‘hans—The surface shall be snsooth and lesel. and impers iota, to paint liquids. The black area shall have a maximum reflectance of I ‘1 and the white area a minimum reflectance of 78 %. The white area shall be non-fluorescent, as observed visually under ultra-violet illumination, or deiernsined in accordance with Practice El 247.
6.2 Balance, accurate to 0.1 mg.
6-3 Glass Slides—Round or square plaes of thickness similar to thai used fix microscope specimen slides, with a nsinitnuns area of 40 cnn
6.4 l’tefleclanrr’Meavar,ng ln’aruntent4—One that allows only diffusely reflected, radiant flux to be incident upon the nwa.suring element. It shall employ a photometric system. including source, fillers, and receptor, that provides a response closely similar lo the prnduci of the spedral luminous cr11’ elency function of the (‘IF standard observer and source C. It shall provide readings to at least the third decimal place and permit estimation to the fourth.
6i Templare.\sith a film area apsroximately 100 cia2 determined to the nearest tenth. Record the exact value on line (‘of the worksheet shown in Fig. I.
6 6 Doctor Blade Film Applicators, width 150 mm. clearances 50. 75. 100. 123. 150. 175. and 200 pm.
6.7 Contpwmer and Software, for solving the relevant ICubelka-Munk t’quations
7. Pnicrdttre
7.1 General lmtraciions:
7.1,1 Film /tpplicurirsit—Make drawdowns manually with a smoudi uniform motion, a the rate of tart 6 cmls. Hold paptr charts flat by a vacuum plate or other suitidile device while making drawdowns.ASTM D2805 pdf download.