| Yellows
The main source of these colours in Britain is yellow ochre; here, the colouration is caused by hydrated ferric iron (the mineral limonite). Many shades occur, varying from pale yellow through 'sienna' to a rich orange, the variations being caused mainly by the varying amounts of limonite present in the different deposits. Good quality strongly coloured yellow ochre frequently occurs in cavities and veins in ironstone deposits, for example, the Jurassic ironstones of Northern, Central and Southern England. Lighter colours can be produced by crushing yellow marls and fine yellow sands where the proportion of limonite is much smaller. For example, an excellent light yellow can be produced by the grinding of fine yellow sands occurring in the Bracklesham Beds (Eocene) of Hampshire and the Isle of Wight.
Reds & Browns
High quality red ochre occurs at many localities and at numerous geological levels, and deposits of economic size have been mined in Soth Wales, Cumberland and Somerset. The colour is caused by ferric iron (the mineral haematite). Many shades of red occur natually, according mainly to the amount of haematite present. Venetian Reds, Indian Reds, and Light Reds can all be obtained. Veins and pockets of a pure deep red ochre occur in the Dolomitic Conglomerate (Triassic) of the Mendip Hills, Somerset. A brownish-maroon pigment can be produced by grinding Triassic Keuper Marl; This out-crops over much of Staffordshire, Cheshire, Warwickshire and Somerset. Here the hermatite is present only in small quantities, and the red colour is 'diluted' by much clay impurity. Deposits of metallic hermatite in the form of 'kidney ore' from Cumberland make excellent reds when finely ground.
Brown pigments ('natural umber' and 'burnt umber') can be made from fossil wood which occurs commonly in some limestones and most clays, especially the Lias Clay and Oxford Clay (Jurassic) which have outcrops ranging across Southern and Central England. True umbers (containing manganese) are rare in Britain. They have been found in Devon, Cornwall and the Isle of Man.
Blues
These colours are difficult to produce from local materials. The only naturally-occurring blue material likely to be encountered in Britain is the hydrated copper carbonate mineral, azurite. This makes a splendid pigment, but is very uncommon, and found only in very small quantities in places such as Cornwall, Cumberland and North Wales. Some Welsh slates are described as 'blue', but when ground the best colour to be hoped for is a murky bluish-grey.
Greens
A most spectacular green can be made from the mineral malachite, a hydrated copper carbonate closely related in composition to azurite but unfortunately, equally uncommon. However, several reasonable greens can be made from grinding rocks which are of wider occurrence. Green slates occur cheifly in Wales, Scotland and the Lake District. When powdered, these give interesting though subdued green colours. The upper and lower Greensand which outcrop beneath the Chalk over much of Southern England owe their colour to the silicate material glauconite; this makes another quite good green. Glauconitic sands also occur in the Brackelsham Beds (Eocene) of the Hampshire Basin and from the green constituent of the Alum Bay Coloured Sands in the Isle of Wight. A different shade of green can be made from the Tea Green Marls (Triassic) which occur above the red Keuper Marls in parts of Central and South Western England. Here, the colour is due to iron in the reduced ferrous state.
Blacks
A satisfactory black can be made by powdering coal. The mineral pyrosulsite (manganese dioxide) when ground yeilds a greyish-black; this mineral occurs in parts of Scotland and Somerset. Graphite can be found in Scotland, but this mineral also produces a greyish black.
Whites
An excellent white can be obtained from the mineral Gypsum (hydrated calcium sulphate). The crystalline form of this mineral (selinite) often occurs as large crystals in clays such as the Oxford Clay and Kmimerig Clay. The variety of Gypsum, 'Satin Spar' and the massive variety, Alabaster, occur mainly in parts of Derbyshire, Stafforshire and Nottinghamshire Barytes (barium sulphate) and celestine (strontium sulphate also make good whites; barytes occurrs widely in Britain, but celestine is resticted largely to parts of Somerset and Gloucestershire. It shoul dbe noted that only pure white specimines of alabaster, barytes and celestine give good whites. Grey or pink matiral is commn but would produce similarly coloured pigments Chalk when finely ground will make an acceptable white.
Preparation of Pigments and Paints
The raw material should be roughly broken up initially and sorted. The selected material, if dry, should then be grushed with a pestle and mortar; damp or wet material should be dried slowly under gentle heat before crushing. Final grinding needs to be carried out with a slab and muller (either of stone or glass) to acheive a fine and uniform grain size. A gum / arabic / water solution (alternatively paper hanging paste) shoul be added to the pigment, if a water colour is to be made. For oil paint and tempera, linseed oil and egg yolk respectively can be added to the pigment, but in all cases should be as small as possible to achieve workable consistency. All paints should be mulled finally on a slab before use to produce maximum dispersion of the pigment particles in the medium.
Bibliography
KELLAWAY B G & KELLAWAY G A 1943 - Pigments for school use made from local rocks and minerals. Athene, vol.2, No.2, pp 63/64.
MAYER, R 1962 - Thge artist's handbook of materials and techniques. Faber.
POCKOCK, R W 1942 - Ochres, umbers and other natural earth pigments of England and Wales. Wartime Pamphlet No.21 Geological Survey of Great Britain.
Images from:
PAVEY, D 1984 - The Artist's Colourmen's Story. Reckitt & Colman. |
