History of Colour Standards

It was determined that a set of permanent, uniform standards were needed which would provide a check on the performance of colour measuring instruments over time, and that calibrated sets were needed to check the absolute accuracy of such instruments.

Why use ceramics as Colour Standards?
The original development was based on the fact that ceramics are inherently very durable and stable. Many artefacts recovered at archaeological sites are ceramic, having survived thousands of years in the soil, at sea or on buildings with little or no change, as seen in many examples from Egypt, Greece and the Roman Empire.

All CERAM Colour Standards are based on a specially developed low expansion tile body, which helps maintain the stability of the finished standards. The profiles are carefully controlled so that the standards present a very slightly convex surface to measuring instruments. This ensures that they make full contact with the measurement apertures.

The glazes are carefully selected to keep surface defects to a minimum while fully developing the colours needed. The finished standards are highly opaque, unlike many other standards available, virtually eliminating measurement changes caused by edge-light loss due to aperture size.

Production is meticulously controlled at all stages, from the application of raw glaze to tile body, through firing at 1050°C, surface selection, ageing, irradiation with UV, colour selection followed by final encapsulation in the backing trays and boxes. All this is carried out by a small team of highly experienced technicians using equipment dedicated to these products.

Fully matt surfaced standards are produced by using a special abrasion technique, developed at CERAM, which ensures an even matt finish across the measurement area. These standards are durable and may be cleaned with care if soiled in use. Their advantage over gloss surfaced standards is that 8/t (Specular Included) and 8/d (Specular Excluded) measurements are virtually identical making measurements easier to carry out accurately.

In response to customer requests, small (50mm square ) standards are available, routinely cut as quarters from the full size tiles or specially cut from the centre. Other shapes are also available, cut to order, as discs or rectangles.

The standards are fixed into trays, using silicone sealant. This prevents ingress of water and contaminants through the back, while the tray's back pattern provides a positive aid to location for repeatable measurement.

The wooden presentation boxes are hand-crafted by a local expert cabinet maker, while the smaller boxes are custom produced for CERAM by a specialist instrument case manufacturer. All full sets of CCSII are also provided with an LCD strip thermometer.

A selection of commercially available tiles were chosen and by 1969, the first sets of standards, named Ceramic Colour Standards, were marketed. The colours used are shown below.

Ceramic Colour Standards (Series I)

The CCS were quickly accepted as the most useful and reliable set of instrument standards available, with manufacturers quoting the accuracy and repeatability of measurement on them as an indication of the merits of their instruments.

Eventually well over 1000 sets were issued worldwide with stocks finally being depleted in 1983.

By the mid 1970s, while the standards were performing well, experience with them was leading the SDC, NPL, and BCRA to discuss how they might be updated to provide a better check on the performance of modern instruments, which were steadily improving. Over the same period pigment and glaze development had taken place which meant that, rather than just updating the old CCS, a new set of CCS could be developed. These would have more consistent finish, better diagnostic value and include two colour difference pairs to check repeatability and reproducibility of colour difference measurements. The new set - CCSII - was developed by BCRA in collaboration with NPL, with SDC supporting the colour difference pairs. This was launched at the 20th Session of the CIE in Amsterdam in 1983.

CERAM Colour Standards (Series II)

The new sets were shown to be very stable and could be used to monitor instruments for spurious readings, lamp faults, long term repeatability and accuracy. Work by NPL and CERAM showed that thermochromism, a reversible colour change with temperature which was due to the steep reflectance slopes on the chromatic standards, was inherent in the colour, not the materials used, and could be corrected by use of published tables of values. A measure of the success of the CCSII was the receipt of the Queens Award for Technological Achievement in 1989.

To date over 3500 sets of CCSII and 25000 White Standards have been issued and demand continues to be steady.

In the years following the launch of the CCSII, new Black and White standards were introduced by CERAM for use in setting up instruments

CERAM continues to develop standards in conjunction with laboratories such as NPL, other research establishments and individual industrial clients. One such example has been the development of a set of standards, in collaboration with the Australian Wool Testing Authority, to attempt to coordinate measurements and set up instruments specifically used in the wool industry. Some of the tiles included form part of a grey scale that we are continuing to develop and which may be used in any industry to check linearity and to set up instruments accurately.

We have a Holmium reflectance standard which can be used to check wavelength accuracy. In addition this standard has a useful feature, in that its colour appearance changes markedly when viewed under different lighting conditions. This is illustrated below, and can be utilised as an extra independent check for lighting in areas where colour assessment is important.

We also have a Black Glass standard (0% Reflectance in 0/45 Geometry).

Finally, following requests from clients, our standards, nominally 5cm or 10cm square, gloss surface, can now be tailored to individual client requirements - for shape, surface finish (matt), size or colour.

Development is an ongoing process and we are always pleased to discuss ways of improving our standards with our clients to improve their usefulness in assessing modern instruments.