Sheen - Opac
Using a standard colorimetric optical geometry this instrument measures
opacity (hiding power) and whiteness. It is ideal for simple shade sorting tasks
e.g. for ceramics or anodised aluminium, where 100 units equals a perfectly
white surface and zero equals a completely black surface.
The instrument measures the diffusely reflected light from the test surface.
The controlled conditions of illumination and angle of illumination allow
surfaces to be characterised according to their lightness or darkness. A
completely black surface will read a (zero), whilst a perfect white will be 100
units, recognised in colour measurement scale as the 'Y' value.
Sheen-Opac can be used for comparison of contrast ratios (hiding power) of
paints. The procedure involves applying the test sample onto black and white
card (our Ref 301) or onto polyester sheets (our Ref 1136) which is then placed
over black and white glass plates. Readings are taken on the coating over the
black portion followed by a reading taken over the white portion.
The readings are expressed as a contrast ratio from the formula : ( Black
: White ) X 100
unit or 1% F.S.D.
button, two standards