Making Hematite Chalk Crayons

August 7th, 2014 § 1 comment § permalink

In 16th century Italy the words matita and lapis were used interchangeably for the word chalk. One of the things I’ve been working on is linking the word matita to the Italian word for hematite. Amatita and amatista are the usual words given in earlier texts for what’s now known as ematite in Italian.

I’ve been particularly focusing on Italian red chalk drawings. The widespread view about red chalk is that artists in Italy began using naturally occurring red chalk in the late 15th century, and that it was replaced by fabricated red chalk, first made in France in the 18th century. The problem with this view is that there is a tremendous variation in color in the red chalk drawings of Italian artists, and references to where the red chalk came from is essentially absent, with the exception of Vasari, who locates the origin to the mountains of Germany. (Post on Vasari and red chalk later.) Naturally occurring art materials very often are paired with geographical indications, such as terra di pozzuoli, terra di siena, bolo armeno and others, but there are no references to lapis di … or matita di … and, to me, this is significant.

Hematite is a major ore of iron, and for a while I was entertaining the idea that red chalk could be a byproduct of iron mining, thinking that the boom in iron (used principally for armaments) coincided with the use of red chalk. That Leonardo and Francesco di Giorgio Martini (see drawings in British Museum, catalogued as having brown chalk underdrawing), could be connected to iron production, and the design of weaponry, seemed interesting. Because of this, I contacted Professor Marco Tizzoni, (cv and publications). He is an archeologist, whose main focus is historic iron mining and metallurgy. Tizzoni recently retired from the University of Bergamo, and is now training archaeologists in ancient mining and metallurgy for the National Archaeological Service of Lombardy (Soprintendenza Archeologica della Lombardia). Our email exchanges and Skype conversations have been invaluable to me.

Professor Tizzoni quickly set me straight. He very patiently explained how matite could not be byproducts of iron mining and smelting, saying, “…. slags are very hard indeed and virtually eternal (it’s funny but man seems to be able to make eternal nasty stuff only, such as slags and plastic).” He seemed even a bit surprised that anyone should think that matite could be anything but fabricated. He went on to say, with more generosity towards mankind, that earlier artists were fully capable of making their own, and that nowhere in Italy could red chalk suitable for writing and drawing be quarried, mined, or dug from the earth. He also added that he is not an expert in writing and drawing materials. My side of the conversation went something like, I know that those artists were very smart and capable of making chalk, and I’m not that dumb that I can’t understand that, but I’ve read over and over again that they were using natural red chalk. Byproduct chalk had seemed like a good possibility, but after conversing with Professor Tizzoni, I had to let that idea go.

Professor Tizzoni then said that I should make my own chalk, that I should experiment. Because of Leonardo’s reference to “lapis amatita macinata” in Institut de France MS A, 104r (link to post), I had looked for recipes for hematite chalk and because of Tizzoni’s encouragement, I’ve made some. It’s a definite plus that there were only three ingredients involved: hematite, water, and gum arabic or fish glue.

The first recipes I found were in English publications, and date to the 1820s. The English recipes, always essentially the same and never attributed to an author, appeared in periodicals such as the Edinburgh Philosophical Journal (1825); and  Iron: An Illustrated Weekly Journal for Iron and Steel Manufacturers, Metallurgists, Mine Proprietors, Engineers, Shipbuilders, Scientists, Capitalists… (1826). After finding the English recipe, I found Italian ones, as for example Lorenzo Marcucci’s Saggio analitico-chimico sopra i colori minerali e mezzi di procurarsi gli artifatti, gli smalti, e le vernici (1816). From the Italian publications, I could see that a certain Sig. Lomet was credited with the recipe, and then looked for his work.

 Antoine François Lomet des Foucauds (1759-1826), who shortened his name for his publishing activities to A.F. Lomet, was an engineer who taught architecture for a short period at Paris’s École Polytechnique, and served in the French military. His recipe, from which a great many others spring, credited or not, is in his article, “Sur la fabrication des crayons de pate de sanguine employés pour le dessin,” Annales de chimie, ou, Recueil de mémoires concernant la chimie et les arts qui en dépendent, (Paris: Joseph de Boffe, 1799), ser.1, v.29-30 1799. His crayons were supposed to be similar to the fort cher chalk of a firm called Desmarest, which must have been a competitor to Conté. He says the cost of making the chalk amounts to a quarter of the cost of Desmarest’s. The recipe’s prime ingredient is sanguine sechè, but oxide rouge de fer is listed as a substitute.

Only recently did I find an English translation from 1800 of Lomet’s article. It appeared in the A Journal of Natural Philosophy, Chemistry and the Arts, Volume 3. It must be because I was fixated on hematite, and in the translation they write ocher or red oxide of iron, that I didn’t find it sooner. I wish I had. Lomet also gives the recipe in ounces and grains (time of metric changeover), which may be found in the article linked above. Here’s a screenshot of the recipe in English, which gives only metric measures.

Screen Shot 2014-08-05 at 15.47.41

Lomet’s Recipe for Chalk Crayons

The important thing about the recipes is that they contain the barest number of ingredients, with no fillers. Hematite surely was increasingly available in 15th and 16th century Italy because of iron mining, particularly in Tuscany and Lombardy. Gum arabic was also widely available.

Just below is an image of the hematite chalks I made. The one on the left was made with 50 grams of hematite and 2.2 grams of gum; and the one on the right with 50 grams of hematite and 3.1 grams of fish glue. I don’t have a scale for small measures, so the amounts should be seen as approximate. Since I’m making the chalks in such small amounts and don’t have the equipment, I have not shaped the chalk by putting it into molds or injecting it into cylinders, as Lomet indicates. I briefly tried stuffing some of the damp chalk material in a piece of tubular pasta lined with baking parchment paper, but soon gave up. The gum one on the left has dried out a bit since I made it. It has become harder to manipulate. Clearly, there’s room for improvement in both types. In the center is red chalk, possibly from Poland. Zecchi, from whom I bought it, wasn’t sure if it was Poland or some other Eastern European country. I do not yet have a porte-crayon and haven’t sharpened any of the chalks.


Hematite Chalk Gum Fish Glue

Top: gum arabic grains, ground hematite, fish glue sheet; Bottom: gum arabic chalk, Zecchi natural red chalk, fish glue chalk

I’ve tried writing on a window with both the gum and fish glue variations, but have not succeeded in leaving a mark. I will try and find some old glass to mark and also to make a softer chalk, using less binder, to try and half follow the glass exercise in Leonardo’s lesson from Institut de France MS A, folio 104r.

The hematite, gum arabic, fish glue, grinding slab and muller were also ordered from Zecchi – Colori – Belle Arti. I learned that their hematite comes from Russia. Massimo Zecchi said that years ago they used to collect hematite from Elba to sell, but the area where the iron quarries were, had been fenced off, and that they hadn’t been back to Elba in many years. Ideally, I would have used Elba hematite, but I haven’t seen it for sale. Professor Tizzoni related that I could buy it from a shop specialized in mineral specimens, which I may eventually do. The idea of grinding down a chunk is a little off-putting (my grinding ability is poor and I lack attention span), although he says hematite can be soft, and even flaky. If I do buy some, I’ll buy it at a shop, where I can feel how hard it is, and not online.

Kremer Pigments also sells natural hematite, both in lump and ground form, and because they list the composition for the ground hematite, I had wanted to order some from them, but they having a warning about its being only for professional users. Nevertheless, to give a general idea of what makes up hematite, below is the composition list of Kremer hematite. I’ve added the column labelled “spelled out,” because, unfortunately, I’ve barely studied any science.

Kremer Hematite -Chemical composition 


Spelled out



iron (III) oxide



silicon dioxide or silica



aluminium oxide



calcium oxide



magnesium oxide



potassium oxide


< 0.1 

titanium oxide


< 0.1 

phosphorous pentoxide


< 0.1

manganese dioxide


< 0.05

sodium oxide



carbon dioxide

H2O (struct.)




< 0.05

sulfur trioxide

I haven’t yet looked at recent conservation studies on the composition of red chalk, but have looked at a paper by Deborah D. Mayer and Pamela B. Vandiver, delivered at a Woodner symposium at the Fogg, and published in the book, Drawings Defined (1987). A pair of sentences in their “Chemical and Structural Analysis of Red Chalks and Hematite,” reads, “Of the samples studied, the proportions of hematite to clay varied from 50-80% hematite and 20-50% clay. Most often hematite and clay were present in equal proportions.” The Kremer Pigment hematite reaches the upper limit. My next post will be about a 16th century source, where kaolin, a clay, is listed as the central ingredient, and the proportion of hematite or hematite-rich material would be smaller. Kaolin is often described in terms of platelets. Mayer and Vandiver use the word platey in their study and see this characteristic as a hallmark of naturally occurring red chalk.

Professor Tizzoni, over the years had collected a great deal of hematite. He recently gave his collection to the University of Pavia, where they are mapping hematite, looking at the chemical composition, the markers, to compile a database on the mineral and its places of origin. He has also collected hematite for France’s CEA (Centre Energie Atomique), which is conducting a similar study. I asked him why my hematite was more brown than red in color. He said that it could be because of impurities, and went on to say, “According to my experience when the ore is shiny, flaky, iron gray and in large crystals its powder is red, when it’s black, opaque, microcrystalline its powder is brownish.” In the same email he added, “Once we made a survey in a big and ancient hematite mine in Lombardy and not only at the end of the day we were entirely covered with shiny tiny flakes of hematite which gave us a rather peculiar look (something more fit for A Midsummer Night’s Dream, I’d say!), but also when we washed ourselves we gave the water a reddish colour.” Of course, I wish my hematite were redder, more like Lombard or Elba hematite, or even a redder Russian hematite, which he says exists. If my hematite were redder, the resulting chalk would look less like chocolate. If small children came to the house, it is something I’d definitely put away.

One further note, fish glue dries very slowly, much more slowly than gum arabic. Leonardo used fish glue in his practice, although I don’t remember it in reference to his chalk or pastels. For the moment, the Biblioteca Leonardiana search term function isn’t working, but I think I remember his using the words “colla di pesce” about six or seven times. My first fish glue batch was disastrous. I used too much fish glue, which was particularly irksome since I blew a full 100 grams of  hematite of my 500 gram total. The resulting chalk is rock-hard and won’t write unless you dip it in vinegar. Then it writes for a short while. Leonardo talks about dissolving chalk in vinegar and then reconstituting it with weak glue/binder/gum* in Institut de France MS F, fol. 104r. Just below is a screenshot and below that is the translation by Jean Paul Richter:


Detail of Leonardo MS F, fol. 96r - reversed - aceto ref

Detail of Leonardo’s Institut de France MS F, fol. 96r – reversed


Chalk dissolves in wine and in vinegar or in aqua fortis and can be
recombined with gum.

*Leonardo uses the term “colla dolce.” Dolce, while it sounds as if it should mean sweet, should instead be read as weak. Recently I’ve been looking at 15th and 16th century medicine-related texts. One of the most interesting is the 1498 Nuovo Ricettario Fiorentino (Bibilioteca Nazionale Centrale di Firenze, Palatino E.6.1.27)a manual providing guidelines as to what Florence pharmacies should stock, including such information as the shell life of items. Olimpia Fittipaldi, an Italian scholar, has transcribed the text of the Nuovo Ricettario and it’s available online in PDF form She also provides an excellent index. Under “Gomme Usuali” or “Commonly Used Gums,” (pages 56-57), the list reads: Myrrha, oppoponacho, pece nera, charabe, ragia di pino, incenso, mastice, bdelio, sandaracha, gomma di cedro, di finocchio, pece grecha, draghanti, trementina, colla di pesce, colla nera, euforbio, armoniacho, gommaedera, ruta, serapino, galbano, storace, gomma arabicha, gomma di abeto, gomma di vino vermiglio, gomma di vino biancho, di ciriegio amareno, di ginepro, di abezzo, pania, orochicho.” There are 32 types of binders. It’s an amazingly long list. As one would expect, the very common fish glue and gum arabic are present. I underlined the red and white wine gums. They must have evaporated most of the water to achieve a gum, or all of it to make a powder. This caught my eye because Leonardo writes of dissolving chalk with wine.

Red Chalk

June 22nd, 2014 § Comments Off on Red Chalk § permalink

Inevitably, talk of red chalk brings up the word blood. In Italian, the word for chalk is matita. It comes from hematite, a mineral and an ore of iron, that traces its name from the Greek word for blood, as in hematology. The French word sanguine, also used in English, comes from the Latin word for blood. Sanguigna is used in Italian, but less commonly than matita rossa. The iron that makes blood red, also makes red chalk red and maybe that’s why the endless testing of the Shroud of Turin never delivers an unequivocal answer. Whatever. Blood turns from anemone-red to a dark brown and the colors of red chalk fall in between.

Hematite is a medium-hard mineral. On the Mohs scale, which rates hardness by one mineral’s ability to scratch another, it comes in at 5-6. The scale is named after its inventor, an Austrian professor of mineralogy, Frederich Mohs (1773 – 1839). It’s a bit like the game of rock-paper-scissors, except that it makes sense and is useful, but it is also less fun. For reference, talc is 1 on the scale; and diamond, the hardest, rates a 10.

Hematite’s outward appearance is more often gray than red. Rock enthusiasts, if they’re in doubt about whether a rock is hematite, will test it by drawing a piece of the mineral across a streak plate, a piece of unglazed porcelain, and if it streaks red, it’s hematite. A piece of hematite, if used for drawing on paper, would do little else but gash the paper. However, it can also be flaky and almost soft. It naturally occurs with other minerals and when it does, it is considerably less hard than its usual 5-6  on the Mohs scale. Red ochre is the umbrella name for earthy pigments that contain hematite. Many of the different names for red ochre are listed in The Pigment Compendium, and include: carnagione [skin tone], sinopia, bol, among others. To this we could add, lapis rosso, which in its most literal sense means red rock. Lapis in modern usage means primarily pencil.

The image below is of a marble slab with the figures done in red ochre. It is usually titled the Knucklebone Players, referring to the girls in the foreground playing a game similar to jacks. Because of the inscriptions on the marble, which includes the name of the artist, Alexandros Athenaios, it’s known that the subject is Niobe pleading with Leto for forgiveness; something that Leto will not give. Niobe’s nervy boast (=hubris) about her having more children than Leto, dooms her children to death. It is from Herculaneum, that together with Pompeii and Stabia, provide the greatest window onto ancient painting. Vesuvius’s eruption created a perfect time capsule of the small cities (combined population of 15-20,000)–the planning, the buildings, the murals, sculpture, and arts of all kinds, as well as documenting the hell-like death of some inhabitants over the course of two days in the late summer of 79 CE.

Alexandros Athenaios - Knucklebone Players - Leto and Niobe

Alexandros Athenaios – Knucklebone Players [Leto Begged for Forgiveness by Niobe, with Three of Her Daughters] – 1st Century CE – Red ochre on marble – 490 x 420 mm – Museo Archeolgico Nazionale di Napoli – inv. 9526

The ancient Romans used the word rubrica for both red ochre and red chalk, and hence  rubrics. There are areas of the Knucklebone Players that look as if they could have been drawn with a pieces of red chalk, rather than painted in red ochre, but it would be very difficult to know for certain. In its present state it is remarkably similar to modern era drawings. There are also traces of pink, yellow, red and black pigment, but these are visible only with a microscope. The hematite-rich part is remarkably fresh, owing to its permanence, its being on the right support–a coarsely surfaced piece of marble–and because of its being buried for so many years. [One could look back further to the well-known prehistoric cave paintings in Spain and France for earlier use of red ochre; to its use in South Africa at the Blombos Cave near Capetown, dating back 100,000 years; and by early Neanderthals at Maastricht-Belvédère in the Netherlands, dating back 200-250,000 years.]

In the medieval period, red chalk was used for writing. Not in the production of the manuscripts themselves (where the red is generally from minium, cinnabar, and vermillion), but for the marginal ticks and notes added by readers. Bernhard Bischoff, who had catalogued thousands of ancient and medieval Latin manuscripts, wrote in his book on Latin palaeography, “Collations, marginal notes by readers, ‘nota’ signs and underlinings with a stylus or red chalk are found nearly everywhere.” Those who used red chalk probably did so because it would stand out from the ink text, making it easier to get back to the annotated section, immeasurably easier than retrieving notes made with a stylus. It might also have been seen as being handier than ink, being quick to pick up and set down, and allowed for reading away from a desk. It was also less permanent than ink and could be rubbed off parchment with pumice. It would be used in much the same way we would annotate in pencil. [Matita, in Italian, in addition to meaning chalk, also means pencil. In fact, if you asked an Italian child what was in their pencil case, they would reply, matite (pl),  referring, even if distantly, to the use of chalk as a writing implement more than to the chalk of drawings.]

The earliest drawing I can think of with red chalk is an anonymous Sienese double-sided drawing in the British Museum. They date it to the late 14th, early 15th century. The single biggest group of earlier 15th century drawings using red chalk is in the Louvre. The drawings are by Pisanello (c. 1395 – c. 1455) and his school. The sheet below shows how red chalk is used in the Louvre drawings–as a tint for the general coloring of the paper. The chalk is used in conjunction with pen and ink, but it is the ink part that is dominant. About a third of the 370-odd Pisanello and school drawings in the Louvre are on paper prepared with red chalk. They originally formed what’s called the red album, the pages of which were then incorporated into what’s known as the Codex Vallardi, after its 19th c. owner.  The red chalk is not limited to sheets with representations of people, but includes leaves with animals, architecture, and objects. It’s worth looking at these drawings to decide for oneself whether any of the chalk is used to model figures and objects. [Link to Louvre site.]

Pisanello - Legs - Plants - Louvre

Antonio Pisanello – Study of the Lower Legs of a Walking Man, Seen from Behind and Two Plant Studies – Black chalk underdrawing, pen and brown ink, brush and brown wash, white chalk heightening on paper irregularly tinted with red chalk wash – 249 x 176 mm – Louvre inv. 2264 recto


Leonardo Madrid II, f. 141v, f. 142r

Leonardo – Madrid II, f. 141v, f. 142r – Biblioteca Nacional de España

Leonardo (1452-1519) is credited with being the first to use red chalk by itself in a drawing. Its appeal came not only from the color, but also from the fact that very fine and precise lines could be made with a sharpened piece of red chalk. So precise that Leonardo used it for writing, and writing entire pages. Two folios from Madrid Codex II, show that his writing in red chalk comes close to his writing in pen and ink, in terms of fineness and clarity. 141v 142 r. Another opening in the codex shows drawings for the wire caging he would need for the projected, but never realized, casting of the monumental bronze Sforza Horse. The wire lacing, with all its intricacy, captivates in a way which you wouldn’t expect from an industrial or shop drawing–except in the hands of this master. The drawing also shows how red chalk can migrate. This is most clearly visible in the unintended ghost of the caging on the left page, made from the contact with the loose chalk dust of the drawing. It also shows why red chalk is so suitable for the transferral of designs, and for the making of counterproofs.

Leonardo - Studies for Casting of Sforza Horse - Madrid Codex II, f. 156v - f. 157r -

Leonardo – Studies for Casting of Sforza Horse – Madrid Codex II, f. 156v – f. 157r – Biblioteca Nacional de España

Leonardo used red chalk for representing many subjects. A name for red ochre is carnagione, or skin tone, showing its suitability for anatomical and figure studies in the related red chalk, of which he made many. He also used the material for all manner of machines, including armaments; geometric shapes; horses; maps; for mountains and storm clouds; for decorative knots; and also for unimaginably beautiful plant studies. The drawing below is of a branched bur-reed and it is very like the plant, in a way that Pisanello’s aren’t (they are generic plants, and while he shows interest in varying the leaf types, the flowers are identical on both plants). The detail of the Leonardo drawing below shows how he accentuated areas by using a brush and water. Where the brush and water traced the lines, the color is intensified, almost acting like an ink. (To see the greatest number of red chalks drawings by Leonardo in one place, it is worth visiting the UK Royal Collection.)

Leonardo Branced Bur-Reed Royal Collection Windsor

Leonardo – A Branched Bur-Reed – c. 1505-1510) – Red chalk, touched with wet brush, on pale red prepared paper – 201 x 143 mm – Royal Collection RC 912430 recto – Windsor

Leonardo - Detail of A Branched Bur-Reed - c. 1505-1510) - Red chalk, touched with wet brush, on pale red prepared paper - 201 x 143 mm - Royal Collection RC 912430 recto - Windsor

Leonardo – Detail of A Branched Bur-Reed – c. 1505-1510) – Red chalk, touched with wet brush, on pale red prepared paper – 201 x 143 mm – Royal Collection RC 912430 recto – Windsor

How Leonardo thought to use red chalk can only be guessed at. He may have quite spontaneously come up with the idea himself. It might have to do with his also being a fresco painter. Widespread appreciation for sinopia drawings came after the 1966 flood in Florence, when so many frescoes were removed from water-soaked walls, exposing the red ochre underdrawings, but the allure of sinopias must also have been felt by the artists themselves. He may have seen drawings by other artists, which are now lost. Another possibility is that artisans might have used red chalk, say in the transferal of designs where symmetry and repeats in patterns were important. Needlework, such as embroidery, comes to mind. It might also have to do with Leonardo’s father being a notaio. The Italian notai, literally notaries, are more like lawyers elsewhere. Their job is to draw up contracts and wills. If nothing else, Leonardo was born into a family where availability of paper and writing instruments was a given. Whether that included red chalk for making annotations and ticking the key points in long contracts, is something that I should look into. However, in my mind, it is increasingly likely that the first users of red chalk were the makers of stained glass windows and/or iron mine workers. I will write another post or two on why I believe this to be the case.

Other artists soon began using red chalk not only to tint paper, but also to draw with the material. First in Milan, among Leonardo’s students and later throughout Italy, helped by the adoption of the medium by Michelangelo, Raphael, and Correggio. The rapid spread is easily understood from the beautiful colors of red chalk.

Red chalk drawings have an animating affect on people. If you look at a group, for example a group following a museum docent around an exhibition, its members will show little signs of life in front of a red chalk drawing. They’ll straighten up or lean in at the drawing. Even at art history slide shows, red chalk drawings have the ability to lift people out of sleepiness like nothing else.

Next – Cennini, Leonado, Vasari, and Armenini on Hematite and Red Chalk

Note: There’s a video of an extremely interesting lecture by Sally Dormer on medieval Anglo-Saxon manuscripts and the drawings they contain. She illustrates a drawing which she believes has a red chalk underdrawing. Link here.


Two Leonardo Drawings at Windsor for a Salvator Mundi

July 9th, 2011 § Comments Off on Two Leonardo Drawings at Windsor for a Salvator Mundi § permalink

Being just as curious as the next guy about the recently attributed panel picture to Leonardo, I thought I’d post images from Windsor of two red chalk preparatory drawings by Leonardo for a Salvator Mundi. Links to the Royal Collection allow for enlargement of the images.

LINK to Leonardo’s Studies of Drapery for a Salvator Mundi at Windsor

LINK to Leonardo’s A Study of Drapery for a Salvator Mundi at Windsor

Leonardo da Vinci (1452-1519) | Studies of drapery for a Salvator Mundi | c.1504-8 | Red chalk with pen and ink and white heightening on pale red prepared paper | 164 x 158 mm | Royal Collection | Windsor

Leonardo da Vinci (1452-1519) | A study of drapery for a Salvator Mundi | c.1504-8 | Red chalk with touches of white chalk and pen and ink on pale red prepared paper 22 x 139 mm | Royal Collection | Windsor

The picture below has just popped up on the internet, a good deal changed, and more believable than the pre-conservation photo.

Attr. to Leonardo | Salvator Mundi | Oil on walnut panel | 65.6 X 45.4 cm | Robert Simon et al. | NYC