Micro-Charring (Charcoal 4)

Micro-Charring for Pigment, Tinder or Medicine

To read about what charcoal is, see The History of Charcoal. To read about the mound method of producing charcoal, see Charcoal Clamps, and to read about the underground method, see Pit Kilns. To read about preserving wood, see Charring Fence Posts.

Apart from its use as a fuel for smelting, smithing and domestic heating, charcoal has a long history of use as pigment, tinder and medicine.

Pigment

Charcoal is a black substance that does not decay; it is completely light-fast (will not fade when exposed to sunlight) and chemically stable (it will not oxidize or change color over time). This makes it very useful in artwork and for writing.

The oldest use of charcoal outside of a hearth was as pigment for drawing and painting on cave walls, more than 30,000 years ago. Sketching with charcoal sticks remained popular throughout human history and continues today. Painting with finely ground charcoal developed into a specialized art in the medieval period, preferentially charring bone or dried grape vines to provide the pigment and using egg white glair, gum arabic or various oils as the binder for black paint. The earliest inks known to man were simple suspensions of ground charcoal in a liquid binder.

According to Cenninni (1), vine black requires the young shoots of the grape vine; he calls this “one of the most perfect pigments we use.” The black created from this char is bluish in tone. He also recommends burning peach stones or almond shells (burning here may be taken to refer to charring, since actual combustion of the material results in ash, not black pigment). Bone black, meanwhile, was one of the deepest, darkest hues of black available to medieval artists. Bone black continued to be favored, as shown by the preference of Rembrandt, who used it in almost all of his paintings, especially as the deepest shadow in the creases of clothing (2). He also used vine black, charcoal and lamp black, but specifically relied upon bone black.

Simple tattoos also rely on charcoal (carbon black) to color shallow scars. Ötzi the Iceman, a 5,300 year old mummy from Italy, had over 60 tattoos colored with carbon black pigment. Modern tribal tattoos still use this method to produce the same results, millennia later.

Tinder

Charring organic material also creates an excellent tinder material. Tinder is important when starting fires from scratch, literally, using iron sulfide (pyrite) and flint strikers. Percussive strikes of flint against iron sulfide create sparks, but these sparks die almost instantly. The fire-maker must therefore carefully aim the short-lived spark into some material that will catch (ignite) quickly, but then stay lit long enough to ignite other material. Ideally, tinder needs to catch immediately from a single spark, and then smolder for a minute or more, while the kindling around it heats to the point of combustion.

Dry wood shavings, moss, fungus, grass and other small kindling can be fluffed enough to serve as tinder if necessary. From early prehistory around the world, the preferred tinder was a specific fungus called touchwood, hoof fungus, tinder fungus, or fomes fomentarius. This fungus was collected from trees, dried, cut into thin slices and beaten into a felt-like material. Ötzi the Iceman carried strips of it in his pouch (3), along with his flint knife, which showed residues of iron sulfide on the back side. F. fomentarius, has been used for millennia, with evidence found in archaeological sites dating as far back as 11,555 years ago (4). However, by the medieval period, Europeans had figured out that the felt strips of this fungus worked even better if charred, first, using small crucibles or clay pots.

The later medieval period saw an improved version of this tinder. The beaten, charred strips of fungus are soaked in “a solution of niter” (5), or salt peter, to create “amadou” or “German tinder.” Salt peter is easily harvested from stale urine; bacteria transformed the urea into calcium nitrate, and a filter of straw and potash provided potassium carbonate, generating a solution rich in potassium nitrate. Soaking the tinder fungus in the salt peter made it more likely to light instantly upon the first contact from a spark. It must be emphasized that this had to be done judiciously, or the tinder would become too volatile and would not smolder slowly, making it less useful for lighting other kindling. It essentially forms a primitive type of black-powder explosive, lacking only sulfur.

Charred fungus was not the only type of char tinder in use, but it is worth noting that there is no evidence whatsoever for charring cloth to make tinder until the 1700's. Charcloth is a useful substance, but only when cloth has become a cheaper resource manufactured industrially. When processing fiber, spinning, warping and weaving a simple tunic took, on average, 4,000 labor hours, the use of fabric for something like starting fires would have been a terrible waste of effort. Plenty of other organic materials worked just as well, and did not ruin such a high-labor investment in the process.

Medicine

The Phoenicians may have been the first to recognize the ability of charcoal as a filter and water purifier, around 400 BCE, but the use of charcoal as a general purifier was already recognized. Some of these uses were likely successful, as charcoal remains a purification and filtration substance in industrial contexts today. For instance, in the Bronze Age a charcoal made from a medicinal fungus, P. betulinus, was a common antiseptic material applied to wounds (6). The ancient Egyptians likewise spread charcoal on festering wounds to draw out pus and infection, as well as to absorb the odor of the rot. Hot charcoal (the tip of a fire drill) was recommended for cauterizing open wounds as early as the 17th century BCE (7), a practice that remained common over 1,000 years later when Hippocrates wrote about pus and wound care (8). Hippocrates used cauterization with a hot coal to burn off tumors of the throat and any unusual growths, as well as burning wounds clean.

Medicinal intake of charcoal in the history was similar to the modern use: absorbing toxins out of the patient's stomach before they can be digested into the bloodstream. There is a limited window of efficacy for blocking ingested poison in this manner, but if the charcoal is given in a timely fashion, the patient may be saved. This use of activated charcoal, and the methods for activating charcoal, are discussed in Pliny the Elder's 36th volume, The Natural History of Stones. Pliny also wrote that oak charcoal could cure carbuncle, convulsions, and contusions of the viscera, as well as neutralizing odors and filtering wine.

Ancient Rome had a multitude of recipes for toothpaste (9), from simple ashes or finely ground burnt pumice, to an abrasive and purifying powder mixed from crushed charcoal, bones, oyster shell and astringent bark. This combination is not too dissimilar from modern toothpaste today.

Powdered charcoal also had a wide range of claimed uses that are less likely to have been effective in medicine (just like today). Dioscorides claimed that charcoal made from wine-soaked ebony was a remedy for itchy eyes, while charred oak galls could stop bleeding, crushed oak charcoal with sumac could cure haemorrhoids, charred salted viper pounded into strips cured nerve disorders, bread dough charred around antimony would heal ulcers and spinal cord bleeding, and burnt salt was a panacea (9).

These recipes typically use standard oak charcoal, or else specify a method for creating small batches of the unique charcoal required for the remedy. In most cases, this latter option involves a clay pot with a fitted lid. In essence, the pot becomes a tiny kiln for the purpose of charring material.

At home method

To make char fibers, bone or vine black:

Acquire a metal tin that closes well. Altoid containers, Seresto collar containers, or other reusable metal boxes work. In an outdoor fire, burn off the printed label and lining from the tin. Note that this is toxic and you should not breathe the fumes.

Punch a small hole in center of the lid with a thin nail. This allows the charring materials to offgas through the vent hole without pushing the lid open.

Cut dry organic material (natural-fiber tinder, bone, or dried grape vines) to fit in the tin.

Pack this material tightly in the tin; less air is better. Close it tightly.

Build a fire. Must be over 350ºC (662ºF). Red hot coals in a campfire will work.

Slowly move the tin into the heat, letting it warm up before inserting it into hottest part of fire. The vent must face upward.

Watch for smoke emerging from the vent hole. Monitor the sides of the crucible; if it opens, the contents will burn up.

When smoke stops, remove the tin from the fire. ALLOW IT TO COOL COMPLETELY. Opening the tin prematurely will ignite contents.

If the material is not fully blackened, close the tin and return it to the fire, monitor, remove, wait for it to cool, and check it again. If the material becomes black and powdery or too fragile for use, it was left too long in the fire. If the material turns white and flaky or powdery, the lid may have lifted during the charring and allowed combustion to occur (or the hole in the top is too large and allowed air in).

Sources:

1) Cennini, Cennino d'Andrea. Il libro dell'arte. 14th century.

2) Kühn, Hermann. “Examination of pigments and grounds used by Rembrandt, analysis carried out on paintings in the Staatlichen Kunstsammlungen Kassel.” Maltechnik/Restauro, vol. 82, p. 25-33, 1976.

3) Pöder, R., Pümpel, T. & Peintner, U. “Mykologische Untersuchungen an der ‘Schwarzen Masse' vom Hauslabjoch.” In Der Mann im Eis. Neue Funde und Ergebnisse, p. 71–76. 1995.

4) Pöder, R., Pümpel, T. & Peintner, U. “The Iceman's Fungi.” Mycological Research,·p. 1153-1162, 1998.

5) Pereira, Jonathan. The Elements of Materia Medica, Part 2. Longman, Orme, Brown, Green and Longmans, p. 574. 1840.

6) Swanton, E. W. (1916). Economic and folk lore notes. Transactions of the British Mycological Society 5, 408–409

7) The Edwin Smith Papyrus: Updated Translation of the Trauma Treatise and Modern Medical Commentaries. Translated by Edmund Meltzer and Gonzalo Sanchez. 2014.

8) Hippocratic Corpus. The Writings of Hippocrates and Galen. Translated by John Redman Coxe, 1846.

9) Dioscorides. De Materia Medica. Translated by Tess Osbaldeston, 1888.