Colour Number: 35
Pigment Details: Hydrated Iron (III) Oxide / Colour Index Pigment Yellow 42 (C.I. PY42)
Yellow Ochre Professional Watercolour is prepared using the synthetic inorganic pigment, ferric oxide hydrate. The pigment has been selected for its light fastness and colour consistancy, making it ideal for use in A J Ludlow’s Professional watercolour range.
Ochres are a family of natural earth pigments containing various amounts of clay, sand and ferric oxide. Since the 1780s, ochres have been processed on an industrial scale to remove the sand and clay and so concentrate the ferric oxide. The process was developed at the ochre mines in Roussillon by the French scientist Jean-Étienne Astier and the resulting iron oxide pigments were exported across Europe and around the world; ochres in their natural state, have not been used as artists’ pigments for a long time.
Yellow ochre is predominately made up of the mineral limonite (the generic formula is generally written as FeO(OH).nH2O), which gives it its yellow colour. Varying amounts of the other two iron ores, hematite (Fe2O3), which is red and the black magnetite (Fe3O4), creates the various shades from yellow to orange or brown. At moderately warm temperatures (around 50oC) in gum Arabic solutions, the crystal structure of limonite changes as it dehydrates to form hematite and so darkens as the red Fe2O3 is formed.
|Brand||A J Ludlow|