Naturally occurring inorganic minerals, including the artists’ earth pigments sienna, red oxide, umber, ochre and terre verte are all iron oxides and have been used as pigments since prehistoric times.126Each pigment displays a wide range of properties, including a large variant of colour shades within each group, which are dependent on the composition of the earth segment from which they came. The earth colour is a result of the nature of the iron oxide. There are a number of factors that determine the
properties of earth pigments, such as the nature of the iron oxide and the amount of
126See James Watrous.1957.110, who gives a partial list of chalks in other colours to be found in nature and Joseph Meder. 1978.86
clay present. The colouring matter in yellow ochre, for example, is mainly hydrated oxide of iron, whereas in red ochres the oxide is in the anhydrous form. The colour of siennas is dependent on the presence of iron oxide and a small amount of manganese oxide. However, it is the particle size and the crystalline shape that influence the pigments visual properties. A clay base is common to nearly all iron oxides. Clay is an important ingredient of natural chalks and what makes them worthy of drawing with, affecting not only the hue but also their softness, hardness and texture. These factors are important in terms of what makes a good chalk for drawing: too hard and it is difficult to make a mark, too soft and the chalk crumbles. The author’s attempts at shaping natural chalks confirmed that some are easier to manipulate than others. A red drawing chalk from France was readily cut into segments and a fine drawing line achieved. French black drawing chalk was harder to cut and produced a hard, fine line.
Raw sienna was also easy to shape and placed in a holder, proving a good drawing tool, (Figure 69). Volcanic red from Italy was very crumbly and too soft to shape and cut, implying that it was not possible to use in its raw state.127
Known generically as the ‘trois crayons’ technique, natural red, black and white chalks are found in European drawings from the later 15thcentury. However, there is a
significant lack of information regarding chalks from the 15thand 16thcenturies, especially with regards to their composition. This issue involves the debate around whether artists fabricated their own chalks or relied on natural ones, with no added ingredients, shaping them, as they needed.128Conservator and drawing materials scholar Thea Burns has investigated this in a comprehensive study of pastel drawing, but there is still little published on the analysis of drawing and other friable media.129 Burns has written extensively on the origin of the word pastel and the confusion around the seemingly interchangeable terminology of chalk, crayon and pastel.130 16th
127Natural chalks for drawing were supplied by Pip Seymour, Fine Art Products, London.
128Artist-craftsmen could be particular about their source of white chalk because of this variation in quality, and what particular job the chalk was needed for. Analysis of fossil remains seem to confirm that certain types of chalk were indeed selected for certain properties, for instance ‘Champagne chalk’ from Northern France was reportedly the best type of chalk for artists. See Unn Plahter,‘The trade in painters' materials in Norway in the Middle Ages. Part II: Materials, techniques and trade from the twelfth century to the mid-fourteenth century ’. Trade in Artists’ Materials: Markets and Commerce in Europe to 1700.
Eds, Jo Kirby, Susie Nash, Joanna Cannon.2010.67
129Thea Burns, The Invention of Pastel Painting, Archetype Publications: London.2007. 8-16
130Thea Burns, ‘Distinguishing Between Chalk and Pastel in Early Drawings’. The Broad Spectrum, Studies in the Materials, Techniques and Conservation of Colour on Paper. Eds. Harriet K Stratis and Britt Salvesen. Archetype Publications Ltd: London. 2002.13
century pharmacists dispensed powders in cakes or pastilles and this has partly led Burns to argue that:
…the term ‘pastel’ was adopted in early modern usage for fabricated chalk sticks because it characterised the method of their fabrication. It did not, in the early centuries, designate an artist’s tool or technical procedure clearly distinguishable from fabricated chalk.131
Burn’s research not only dispelled Watrous’ assertion that the only natural chalks of any importance within the technical history of drawing were red, black and white,132 but also demonstrated that prior to the burgeoning of pastel drawings in the 18th
century, there was a broad range of naturally occurring coloured chalks, something that has not really been acknowledged to its full extent before.133 The range of hues within each basic colour category illustrates this and can be seen in Holbein’s portrait
drawings. For example, the red chalks that he used range from the crimson red of the flesh tones used in Basel for his 1516 portraits of the Jacob Meyer and his wife
Dorothea, (Figures 1 & 2), to the russet red of the clothing of William Warham in 1527, drawn during his first visit to England, (Figure 10). Thea Burns has suggested that the assumed limited range of naturally occurring coloured chalks is what has led to the supposition of fabrication of sticks of chalk or pastel in the first place, but it may be that this was not always necessary.134We should therefore keep an open mind about the existence and obtainability of a wider colour range of natural chalks and not just assume Holbein used fabricated chalks.
Depending on the physical characteristics, naturally occurring coloured chalk-like minerals such as ochres can be shaped into a point or cut and formed into a stick and used as a drawing tool.135 For example, natural earths may already include some impurities such as clay, which would serve as extenders and make them soft enough to draw with.136 If the consistency of these chalks were not ideal for drawing, then these
131Thea Burns.2007. 8
132 James Watrous.1957.110
133See also Thea Burns, ‘Chalk or Pastel? The use of coloured media in early drawings’. The Paper Conservator.1994. 18.51
134Thea Burns.2002.13
135Thea Burns.1994.49-56
136Joyce H Townsend, ‘Analysis of Chalk and Pastel Materials’. The Paper Conservator, The Journal of the Institute of Paper Conservation. 1998. 22.21
chalk-like minerals could be powdered and fashioned into cohesive sticks with the addition of a binder such as gum arabic.137 These are known as ‘fabricated’ chalks. The distinction between pastel and fabricated chalk in the early modern period then is intangible. Pastels were not available commercially until 18thcentury, by which time many other coloured pigments were being used. This resulted in the creation of drawings in full colour: something that Holbein was not able to do in dry media, and perhaps accounts for the many notations on colour found on his drawings. The array of hues within the restricted colour range of red and yellow alone indicate that Holbein could obtain chalks from naturally occurring deposits but whether they were then made up into sticks is not clear.
There is a question around whether Holbein’s chalks were used in their natural state -cut into points or sticks - or fabricated. Within the natural chalk colour range, it is very difficult if not impossible without instrumental analysis to visually distinguish between fabricated and natural chalks in Holbein’s work. The presence of unnatural additives or organic binders usually indicates that the drawing chalk in question is fabricated, although they often appear in quantities too small to analyse without the aid of an electron-scanning microscope.138However, taking samples of the dry media on Holbein’s drawings was not possible and visual examination did not clarify if the chalks were fabricated or not.
The sparsity of the chalks often rendered Raman analysis inconclusive in terms of pigment identification. Further it was not able to distinguish some pigments because of the dominance of the vermilion in the preparation that overwhelmed potential
readings. However, whilst this research has not been able to clarify if the chalks were fabricated or not, the spectrum of Holbein’s dry media fits within the natural chalk colour range. Holbein used chalks in variations of reds, browns, and yellows, black and very occasionally white, to execute his portrait drawings. He also blended the chalks as he drew. It is this tonal range that has resulted in Holbein’s drawings being associated with fabricated chalks in art historical literature.139
137Thea Burns.2002.12
138Joyce H Townsend.1998.22.
139For example, Susan Foister. Drawings by Holbein from The Royal Library, Windsor Castle, with an introduction & catalogue by Susan Foister. Johnson Reprint Co. Ltd, Harcourt Brace Jovanovich: London.
1983. Limited Edition in two volumes.29 and see Marjorie Shelley, ‘An Aesthetic Overview of the Pastel