Computer Colour Matching Questions and Answers

Answer: C

Both are true and the reason gives the dependence, and recalibration is periodically required. Changes in dye lot or substrate both degrade the database. Prediction is only as good as its data. Recalibration is periodically necessary.

Answer: D

Correct answer: 1 and 2 only

Statements 1 and 2 go together: dye lots vary in strength, substrates change, and the database drifts out of agreement with reality unless it is refreshed. Statement 3 is the assumption behind most matching systems that stop working - a database is a record of how things behaved when it was built, not a permanent property of the colourants.

Answer: A

It generally requires the same colourants as the standard used. The resulting recipe is more expensive but far more robust to a change of conditions. The same colourants are usually needed. Robustness is bought at some cost.

Answer: B

Both are true and the reason gives the mechanism, and the cheapest listed recipe is a starting point rather than a decision. A combination may cost least yet contain a colourant with poor light fastness, or one dosed at a weight too small to dispense accurately. The colourist applies those constraints after the ranking is produced.

Answer: C

Correct answer: it predicts the whole reflectance curve rather than three values

Because the calculation runs wavelength by wavelength, each candidate recipe comes with a complete predicted reflectance curve. That curve can then be integrated under any illuminant, and comparing the results under two illuminants gives the metamerism index - something impossible if only tristimulus values had been predicted.

Answer: D

The first two are correct and are standard software features. The third is out of date, since prediction has allowed pre-selection for decades now. Candidates can be ranked before any dyeing. Pre-selection has been possible for decades.

Answer: A

A different white base gives a different result from the same recipe. Substrate reflectance is measured and stored alongside the colourant data. A different base gives a different result. Substrate reflectance is stored with the data.

Answer: B

Both are true and the reason gives the dependence, and the dye may also behave differently. Separate calibration per substrate is the usual arrangement. The dye may also behave differently on it. Separate calibration per substrate is usual.

Answer: C

Two constant theory and careful sample preparation are both required. Processing conditions can also alter the dispersion and hence the colour. Two constant theory is required for pigments. Dispersion affects the colour developed.

Answer: D

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the mechanism. The colour of a pigmented plastic depends on how finely and evenly the pigment is dispersed, and dispersion is achieved by shear and heat during compounding and moulding. Change the screw speed, the temperature or the residence time and the same formulation gives a different colour.