The latest updates from Unison Colour

All about our pigments.

14 April 2016

Our pigments are as interesting as what we do with them. This is their story.


Here at Unison Colour, we use traditional pigments, which are incredibly light fast. All the pigments we use have a light-fastness of at least ninety-eight per cent. This is why paintings in pastel look as fresh as the day they were finished, even if they were drawn hundreds of years ago. Traditional pigments are known also for their great luminosity and coverage.


Sourcing the pigments was one of the most difficult things when we started making pastels nearly thirty years ago. The internet had not been invented, and so a great deal of time was spent on the telephone trying to find suppliers of the best quality pigments. Today it is much easier and we source the best from the U.K., Italy, the U.S.A., Germany and China.



 Among the pigments we use are viridian, cobalt, titanium, cadmiums, ultramarine and earths.


Viridian is a blue-green pigment, a hydrated chromium-oxide, and relatively dark in value. It is more green than blue. It is actually a dark shade of spring green. Viridian takes its name from the Latin ‘viridis’, meaning ‘green’.


Cobalt is a lustrous, silvery-blue metal. It is magnetic. Cobalt pigments are blue and violet.



Titanium is a white pigment which only became available for artistic purposes in the twentieth century. Although the titanium pigment, titanium dioxide was discovered in 1821 but it was not until 1921 that a suitable titanium white was introduced by both American and Norwegian manufacturers.


Cadmium pigments are red, orange and yellow. Although there was some concern over cadmium pigments, they have undergone stringent E.U. risk assessment in 2015 and are fully REACH registered. They are of no risk to people or the environment and have been classified as non-hazardous.


Earths are literally dug out of the ground! These colours can be traced back as far as 30,000 year old rupestrian inscriptions, and to ancient Greek-Roman frescos. So they stand the test of time! Earths also have an unusual quality in that they can be mixed with many different carriers. This gives them a great versatility. Favoured especially for wall colourings due to their stability, resistance and brightness, these natural earths have many uses from restoration, lacquering, plaster, and art materials. Most of the colours, except for the black earth, contain iron. After quarrying and drying, each earth needs a different working process. Some of them are coarsely crushed, impurities removed and then made finer by hammer or ball mills. Other earths are burnt, which changes the mineralogy and gives many tones. Different colours are caused also by natural processes such as rock dissolution by water, volcanic activity, or calcination.



Ultramarine is a deep-blue coloured pigment which was originally made by grinding lapis lazuli into a powder. The name comes from the Latin ‘ultramarinus’, which means ‘beyond the sea’, because the pigment was imported from Afghanistan by Italian traders during the 14th and 15th centuries. Ultramarine is famous for having been the most expensive pigment. It was more expensive than gold during the Renaissance and often reserved for the cloaks of Christ and the Virgin. Because of its expense, chemists were requested to find a synthetic ultramarine as early as the 1700’s. In 1787, Goethe was one of the first to observe the blue deposits on the walls of lime kilns near Palermo in Italy. He was aware of the use of these glassy deposits as a substitute to lapis lazuli. The blue deposits were also taken from the Saint Gobain glassworks by Tessäert, who found them in a soda furnace. He gave his blue samples to Vauquelin. In 1814, Vauquelin published his findings that the blue masses were similar in composition to the costly lapis lazuli. In 1824, the Societé d'Encouragement offered a prize of six thousand francs to anyone who could produce a synthetic variety not to exceed three hundred francs per kilo. The prize was not awarded for four years, but eventually in 1828, the prize was awarded to Guimet who submitted a process he had secretly developed in 1826. Guimet's ultramarine was sold for four hundred francs per pound. Lapis lazuli cost between three to five thousand francs per pound at that time! Gmelin, also a professor in chemistry, discovered a slightly different process, which he published only one month after Guimet.  Gmelin claimed that he beat Guimet.  By about 1830’s both Guimet's and Gmelin’s ultramarines were being produced in France and Germany.

Our pastels are second-to-none, because of these wonderful pigments that are still available to this day!





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