Additive and Subtractive Mixing Questions and Answers

Answer: A

Both are true and the reason gives the distinction, and blueing necessarily darkens the substrate. Brightening adds light and therefore does not. One darkens the substrate and one does not. Fluorescence adds light to the reflected beam.

Answer: B

Multi-angle instruments are needed to characterise them adequately. A single measurement geometry captures only one aspect of a goniochromatic material. Several angles are needed to characterise it. A single geometry captures only one aspect.

Answer: C

Both are true and the reason gives the necessity, and a single reading is inadequate. Automotive finishes are the commonest commercial example. A single reading cannot describe such a finish. Automotive coatings are the usual example.

Answer: D

The substrate contributes to the final appearance in a way it does not for opaque films. Glazing in painting exploits exactly this property. The substrate contributes to the final appearance. Glazing depends on exactly this behaviour.

Answer: A

Correct answer: A-2, B-4, C-1, D-3

The two coefficients of Kubelka Munk sort the colourants out. A transparent dye absorbs and barely scatters. An opaque pigment does both strongly, which is why it hides. A white pigment scatters strongly and absorbs almost nothing, which is what makes it white and opaque at once. And a black pigment absorbs strongly and scatters almost nothing.

Answer: B

Both are true and the reason gives the contrast, and hiding power follows from scattering. Kubelka Munk handles the two coefficients independently. Hiding power follows from scattering alone. Absorption and scattering are separate properties.

Answer: C

Correct answer: the scattering coefficient of the pigment used

Hiding comes from turning light back before it reaches the substrate, which is scattering, and titanium dioxide is used precisely because its high refractive index scatters so effectively. Absorption darkens the film without necessarily hiding what is beneath - which is why a transparent dye can be intensely coloured and hide nothing at all.

Answer: D

The first two are correct and describe the property. The third confuses absorption with scattering, which are separate and independently variable quantities. Tinting strength depends on absorption. Hiding power depends on scattering instead.

Answer: A

Correct answer: lighter and less saturated than the original colour

White pigment scatters light back at all wavelengths, which raises the lightness and dilutes the selective absorption that produced the colour. Both effects move the colour towards white, so a tint is always paler and duller. Only a source of light, not a scatterer, could raise lightness without loss of chroma.

Answer: B

These terms are used consistently in colourant practice. Each moves the colour in a different direction within the colour solid. The vocabulary is used consistently in practice. Each addition moves the colour differently.