ISO 2813:1997 pdf free download.Paints and varnishes — Determination of specular gloss of non-metallic paint films at 200, 60° and 85°.
The pnmary reference standard shall be highly polished quartz glass or black glass, the top surface being piano to within two fnnges per centimetre, as measured by optical-interference methods.
NOTE 8 It is not intondod that the primary reference standards be used for dady calibration of glossmeters.
Glass with a refractive index, measured at a wavelength of 587,6 rim, of 1,567 shall be assigned the specular-gloss value of 100. If glass of this retraclive index is not available, a correction is needed. Values of specular gloss for polished qrt glass and black glass of venous refractive indices at the three angles of incidence are given in table 2.
The primary standard shall be checked at least every twO years because of the possibility of ageing. This is esoecialtv aboheable for black alass. In the event of degradation, the original gloss can be restored by optical polishing with cerium oxide.
NOTES
q The most rciadlly available glass of the required planartty le now manulaclured by the floar process. This glass is unsuitable for use as a primary reference standard because the refractive mdcx of tho bulk of the glass differs from that of the surface, It Is preferable to use an optically plane glass made by some other process, or to remove the surface of the float glass and repohsh to optical planartty
10 The refractive index should preferably be determined by means of an Abbe refractometer.
11 If the absolute reflectance of the primary rntPrAnca standard is required, me Fresnel equation may be usec, inserting the retractive index of the standard in the equation.