"Transparent Umber is a colour with the ??Oh Wow?? factor. The earth colours have generally changed very little overt the millennia and artists tend to think of earth colours as all being ancient in origin but the situation is more complex than that. Raw Sienna and Raw Umber as found in a modern tube of paint is virtually identical to the Raw Sienna and Raw Umber used 18,000 years ago by artists in caves in France. Red Oxide and Yellow Oxide have improved in purity during the 20th century by being made synthetically but the difference between the natural and the synthetic products are relatively small. Transparent Umber, however is genuinely different. There is no natural pigment that looks and behaves in a similar manner and it is totally an invention of the modern chemical industry in response to the demand of automobile manufacturers for new colours. Since cars typically are exposed to direct sunlight for 10 or more years pigments used in auto paints need to have exceptional resistance to light. Transparent Red Oxide and Transparent Yellow Oxide fitted the requirements of colour beauty as well as absolute stability in light and so extending the colour range of the transparent iron oxides into the dark brown range was a logical next step. The synthetic transparent iron oxides gain their transparency very differently to natural earths. The natural iron oxides have large and irregular pigment particles which are naturally opaque, but a natural yellow ochre can have as little as 20% yellow iron oxide in it. These colours are never as transparent as Transparent Yellow Oxide, but they can be semi-transparent due to the matrix the yellow iron oxide is in which can be transparent silicates. The synthetic oxides, on the other hand are pure and any transparency is due to pigment particle size. Where the particles are exceptionally small the pigment becomes transparent. This is of great benefit to the artist since these transparent iron oxides have exceptional beauty.
As much as artists tend to adore beautiful colours, it is the usefulness of that colour that determines whether or not it has a place in the artist???s paintbox. In the case of Transparent Umber it is so useful it is possible to larges replace Burnt Umber with it. In many ways the colour behaves as the original Van Dyke Brown did back when Rubens and Van Dyke were using it. Unlike the more opaque pigment that has inherited the Van Dyke name, the original was very transparent and it was this transparency which Rubens particularly valued. Unfortunately that transparency came at a cost because the natural ingredients of the colour were not as permanent as Rubens might have hoped. He would therefore have embraced our modern Transparent Umber with open arms since he would get the transparency he desired along with permanence as good as the best of the earth colours.
One of the most important uses for a transparent dark brown is for laying in the basic tonal structure of a painting over an imprimatura (initial stain of colour painted on a ground) of a thin layer of Raw Umber. In the vocabulary of the old masters darks should ideally be thin and transparent while the mid tones and lights in the picture should be progressively more opaque and thicker with impasto reserved for the lightest highlights. While oil painters have abandoned such techniques for over a hundred years due to the time involved in waiting for successive layers of oil paint to dry, the fast drying of acrylics enables modern painters to re-look at some of the older techniques. Acrylics tend to benefit from layering of colour since the paint has less body than oil paint does, but building acrylic in layers gives it great depth and richness of colour.
Transparent Umber should be used much like Burnt Umber is, as a darkener of other colours. Due to the great transparency of this colour, however, there is a particularly beautiful undertone when mixed with other transparent colours.