All highly coloured materials are subject to thermochromism to varying degrees.
This reversible change in colour with temperature has been a problem with many standards but can be overcome in the CCSII by use of Thermochromic Correction data determined by the National Physical Laboratory. The basic data is supplied free with sets of CCSII.
The changes in CIEL*a*b* for a 10°C rise in temperature for Specular Included, Illuminant D65/10 degree Observer are shown below:
|D L*||D a*||D b*|
Changes for Specular Excluded and 0/45 are similar.
More detail is available from the paper below:
'The BCRA - NPL Ceramic Colour Standards, Series II - Master spectral reflectance and thermochromism data' by F.Malkin, J.A.Larkin, J.F.Verrill and R.H.Wardman published in the Journal of the Society of Dyers and Colourists, Vol 113, March 1997.