Ceramic colour standards The British ceramic industry, in collaboration with the British Ceramic Research Association, the National Physical Laboratory and the Society of Dyers and Colourists has produced a set of 12 coloured tiles for the calibration and control of colour measuring instruments. Such tiles will be o[ considerable value wherever colour measurement is carried out. For example they can be used to indicate how accurate a colorimeter is, i.e. how closely it determines XYZ values or how precise it is, i.e. how reproducible measurements are they can reveal the agreement between different instruments of either the same or different models they can show when an instrument is no longer performing correctly. The choice of the twelve was governed by a number of factors. Perman- ence, temperature insensitivity, and absence of fluorescence in the 300-700 nm region, were essential from the tiles which possessed these qualities, 12 were chosen to cover a reasonably wide region of colour space including three neutral greys and in order to provide the maximum value in diagnosing instrumental faults, the shapes of the reflectance curves were taken into consideration as well as the colour of the tile. One batch of tiles was made for each colour under the most stringent control possible, and 1,000 tiles for general sale were selected from the batch by visual inspection to ensure freedom from significant blemishes. From these 1,000, 50 sets were specially selected for sale as NPL-calibrated standards, the most representative being designated the Master Set. Calibration data of the Master Set will be determined at the National Physical Laboratory as accurately as possible and this will be supplied with each uncalibrated set to indicate approximate values. It is believed that the variations between the selected tiles of each colour will be small enough to be ignored for many purposes. Where greater accuracy is required the NPL-calibrated standards should be used. Uncalibrated sets of ceramic colour standards can be obtained from:- The British Ceramic Tile Council, Federation House, Station Road, Stoke-on-Trent, England. 49

5O JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS and sets of NPL-calibrated tiles from:- Metrology Centre, The National Physical Laboratory, Teddington, Middlesex, England. The ceramic tile standards cost oe7 per set, the NPL-calibrated tiles, from f70, both prices including postage to any part of the United t(ingdom, otherwise they are f.o.b.