Painted Steel Panels for Measuring the Hiding Power of Powder Coatings and Industrial Enamels
Black Surface: Solvent Resistant, Non-Bleeding, Reflectance – 1% maximum. Measured using ASTM Method E 1347
White Surface: Solvent Resistant, Color Retentive, Reflectance – 80% minimum. Measured using ASTM Method E 1347
Major uses include:
ASTM Method D 6441 – Measuring the Hiding Power of Powder Coatings – A wedge shape film is applied on a T12G or T12M panel. Points of specified film thickness are located over the black and white areas, reflectances are measured and the mean contrast ratio at that film thickness is calculated. Alternatively, several black/white pairs of equal-thickness points at various film thicknesses are located, and the calculated contrast ratio plotted graphically against the film thickness to obtain the film thickness at a contrast ratio of 0.98. In this method the reflectance is measured with a small diameter aperture (e.g. 4 mm), and the film thickness with an electronic film thickness gage.
Powder Coatings Institute Method – In this method the film thickness is determined directly on a T12G panel at 0.98 Contrast Ratio. Alternatively, the Contrast Ratio is determined at a specified film thickness. Reflectance and film thickness instrumentation are as in ASTM D 6441.
ASTM Method D 2805 – Hiding Power of Paints by Reflectometry – The film is applied uniformly over a panel. The film weight and reflectance R0 are determined on the black area, and the reflectivity R∞ of the coating determined using the black and white areas. The gravimetric spreading rate at 0.98 Contrast Ratio is then calculated using Kubelka-Munk equations. Conversion to volumetric spreading rate or to film thickness is readily accomplished.