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.