SEE INVISIBLE TO BE ABLE TO UNDERSTAND THE VISIBLE
Beneath its gullied surface, the wood hides well secrets which tell its history. How to decrypt what is invisible so as to be able to understand what is visible?
View of the carved surface of a Borneo Hampatong. Photos Jean-François Chavanne. Microscopic view (SEM) of the macrotexture of wood near the sculpted surface, 101x magnification, sample P3. Courtesy LAMOA Expertise.
Usually, a C14 data is enough to establish the date of the wood used in a tribal piece of art. The famous art gallery director and collector Hélène Leloup, specialist of Dogon art, curator for the Dogon exhibition at the quay Branly’s museum in 2011 and president of honor of “Parcours des Mondes” 2013, declared in an interview “to advocate the virtues of using C14 to date the age of the wood with which were made the statues”. In another article the title of which is “Carbon 14, to give a date to tribal art”, Bernard Dulon, a Parisian merchant, testifies, as for him, that “age finding through carbon 14 dating is totally adapted to the detection of false pieces of art especially in tribal art”. Indeed, the use of carbon 14 to give an objective datum about the wood used for a sculpture of tribal art, gives also, by consequence, the object’s age for the woodcarvers work on green wood, flexible and unbreakable, for technical but also religious (see here) reasons. Nevertheless, this date only gives an average age that, as useful as it may be, needs sometimes to be completed by other datum: the composition of the ritual patina, the wood which was used, the processing methods, the traces left by the tools, the clues concerning its use, even the accidents, etc. are important quality data, rich in lessons and complementary to C14.
In scientific language, this is called "a search for clues to determine if the object has undergone a natural aging long after the sculpture phase".
-Marie-Pierre Etcheverry. LAMOA Expertise. study objective of Borneo wood sculpture. LAMOA 12-18 OA. 2008-
It is within this framework that a scientific investigation has been lead on the big Hampatong of Bornéo, presented during the “Parcours des Mondes” 2013. The use-wear analysis and dendrochronological studies done by Catherine Lavier and Victoria Asensis Amoros (here) bring their lot of technical informations and ethnographic studies, specially concerning execution methods and the technics used. Reading wood is the work of specialists! But, many other informations, impossible to be seen by a bare eye, are hidden in the wood, and it is sometimes essential to know them. As for this sculpture, which has a marginal esthetic in the known corpus of the data using C14 and the xylologic and archaeodendrometric studies of Dr. Victoria Asensis Amoros and Catherine Lavier, it is crucial to know if the processing of this object has been realized immediately after its being cut down or much late on a “recycled” wood(3). In a scientific language, this is called “a search of clues allowing to determine if the object has aged naturally on a long length of time after being carved”. In a trivial way, we could use the following words: do we have in front of our eyes a “fantasy” carved in an old piece of wood?
Surface carved a Borneo Hampatong from a river and dated by C14, 15th century. Photos Jean-François Chavanne.
To answer this question, the laboratory Lamoa expertise is going to explore the depths of this discovery by the intervention of its director, Marie-Pierre Etcheverry, doctor in Physics applied to archeology at the University of Bordeaux and engineer archeometre in the Centre of Physics applied to archeology / CNRS UMR 5060, by questioning the artefact’s raw material : the wood. The material resources used are impressing: portable microscope, optical stereo microscope and electronic sweeping microscope, with imaging electron radio broadcast fashion (E.R.B. with chemical contraste) coupled with an elementary analysis using energy dispersive x-ray spectrography. All these “barbaric” names, which do not mean anything to us neophytes, in reality, hide sophisticated and proved investigation technics, applied in sectors as different as industry, assurance policies, criminal investigations and of course Art history.
Traceology: observations and conclusions
No trace left, the sharpness and the freshness of which might evoke a modern handcraft or the pursuit of a carving work is visible, although the density and the hardness of the Shorea known for its difficulty to be worked upon.
-Marie-Pierre Etcheverry. LAMOA Expertise. Etude des traces de façonnage et d'outils. LAMOA 12-18 OA. 2008-
This Hamptong’s wood exploration begins by preliminary optical observations. This first step observes globally, at a microscopic scale, the same phenomenon as those observed by xylodata (here). The wood shows several signs of a probable and important brutal hygrometric variation that is characterized by many visible cracks on the whole surface of different degrees. The big crack that goes across its back, from bottom to top, for example, is one of the direct consequences of the wood’s desiccation (drying). This type of crack is currently found on many wooden tribal art objects whatever be the continent it is from. In several spots, the local subsidence of the outer wall of the ligneous vessels, phenomenon that leads to a deep hollow in the wood, has obviously occurred naturally for we detect no signs of mechanic aggression, like those made by tools for example. This alteration of the wood’s structure itself corresponds to natural aging manifestations occurred after the phase of carving. No trace left, the sharpness and the freshness of which might evoke a modern handcraft or the pursuit of a carving work is visible, although the density and the hardness of the Shorea known for its difficulty to be worked upon. On the contrary, the pronounced smoothing of the shape as well as the traces and cuts linked to the tools used when worked upon by the artist disappear under the pronounced time wear. Here again, the phenomenon offers the appearance of a slow and progressive degradation process after the processing work.
Left to right. Detailed view of the sculpted surface to portable microscope. Fractures resulting deep internal mechanical tensions with mineral deposits prisoners. Cracks withdrawal characteristics of an important dryness of the wood.Courtesy LAMOA Expertise.
In its original context, after the tree being cut down, the sculpture is quickly processed by the artist in a precise ritual surrounding. Once finished, the Hampatong is erected where it will be used and where it will be exposed alternately to pouring rain and to intense equatorial sunshine. Its surface temperature is going to fluctuate in considerable proportions. In Boneo’s villages, the architectural elements realized in iron-wood, like terraces and loggias, pontoon ladders are so hot at certain hours of the day that it is impossible to walk on it barefooted without getting burnt. This daily alternate change between intensive pouring rain and exposure to strong sunshine is the origin of these phenomena of the wood’s alteration, the observable cracks on this sculpture as well as most of the Hampatongs exposed to outdoors air. Under the uninterrupted assaults of this hostile environment, the wood being to solid it leads to it breaking in cracks. Well known for its solidity and its resistance, the Shorea, as well as other essences called “iron-wood”, is very slowly affected by these continuous intensive climatic variations. Capable to resist such conditions, the statue’s wood stays stable without losing its shape more than what is normal. These mechanical qualities (see here), moreover, have not gone unnoticed by the dayak artists. The first stage of life of this piece of art has thus taken place outdoors, where it would be used, most certainly, as long as the village was inhabited.
Torrential rain spontaneous on the Upper Mahakam, Kalimantan Timur, Borneo, Indonesia. The equatorial climate of Borneo is a succession of heavy rain and scorching sunshine. Copyright Bertrand Claude.
A dive beneath the wood’s surface
The second stage of this investigation in an immersion into the matter’s heart, under the wood’s surface, beyond what intuition and experience can guess. It is exploring the wood’s memory. To do so, three samples are being withdrawn from different parts of the statue so as to characterize the carved surface and to study the average age of the carving work. The first, P1, is taken from behind the top of the head; the second, P2, from the right side of the lower part of the trunk and the third, P3, under the right buttock. The spots where these samples have been taken from, allow to cover three well distinctive exposed zones. Whether it be during its customary life outdoor or during its long stay at the bottom of the river, this hampatong’s surface has not received uniformly the aggressions of each of these environments. On each sample, a brown crust of superficial deposit, sometimes lacunar, covers the wood’s surface. Generally cracked and a dozen micron thick, it allows to see, in certain spots, the darkened wood. This crust, observed with a sweeping electronic microscope (SEM), using a chemical contrast mode, is relatively homogenous. Its elementary composition chows a mineral deposit composed of silicon (Si) and aluminum (Al) enriched with iron, calcium (Ca), potassium (K), magnesium (Mg) and sulfur (S), plus a few traces of titanium (Ti) and of manganese (Mn) locally. All the component of a mineral water coming from a spring or a mountain stream!
Left to right. Sampling P1. Area of the sculpted surface covered with superficial deposits (MEB-ERD x427). EDX spectra of representative analysis of the elemental composition of the natural calcium inclusions detected in the portions near the sculpted surface (a) and in the inner parts (b). Courtesy LAMOA Expertise.
At this pellicle (which covers small mineral particles), hidden in crevices, microscopic skeletons appear. Their identification is immediate and without appeal! These are diatoms!
When approaching these different piles of very little mineral particles composing this deposit, we discover that they are covered by a thin “linking” coat of organic appearance. Under the scanning microscope’s stern lens, magnification x 640, traces of life appear! Regarding this thin coat, hidden in crevices, microscopic skeletons spring out. Their identification is immediate and without appeal! They are diatoms! “The presence of these unicellular planktonic microalgae as well as the morphology (fine particles) and the deposit’s composition show that they are aquatic sediments”. Here we are! This statue has indeed stayed in an aquatic surrounding. It is evident, but how long? These microalgae, major component of the phytoplankton and food base for multiple aquatic ecosystems, have colonized this wood during its long immersion. The presence of diatoms in this “moist wood” (4) attests of its long stay in one of Borneo’s rivers during a time that the scientists name an “archeological time”!.
Microtexture MEB of the fine brown crust deposits present on the surface of the sculpture. Left. sediments and diatom - ERD x 640. Right. detail of a diatomaceous area - ERD x 1730. Courtesy LAMOA Expertise.
Furthermore, several studies having shown that the wood gorged with water (waterlogged woods) had a tendency to be especially enriched with iron and sulfur, we think that these phenomena of enrichment could establish here a sort of indicator of a natural aging process of the carved surface which could have happened during its stay in an aquatic surrounding.
-Marie-Pierre Etcheverry. LAMOA Expertise. Study of a Borneo wood sculpture. LAMOA 12-18 OA. 2008-
Under this mineral crust, the sculpted area itself appears, but it is difficult to obverse. The cells which form the wood’s web are often distorted, altered. “This phenomenon indicates that the wood used presents an identified alteration furthermore like a process of delignification”. The lignin is an extremely resistant material against different chemical agents and biologic degradation. Its natural decomposition is an extremely slow process. In the areas near the carved surface and nearby, the ligneous cells of the wood used are deteriorated, their sides destructed and we can identify stigmata coming from probable local attacks by micro-organisms. Here, the examined pieces have the particularity of being enriched with iron and sulfur (S). These two exogenous factors have probably migrated from the superficial deposits of the crust to the heart of the wood. “Furthermore, several studies having shown that the wood gorged with water (waterlogged woods) had a tendency to be especially enriched with iron and sulfur, we think that these phenomena of enrichment could establish here a sort of indicator of a natural aging process of the carved surface which could have happened during its stay in an aquatic surrounding”. In the sample taken from the top of the head, we observe a variation of the composition of these calcic phases, enriched in a significant way with iron, sulfur(S) and aluminum (Al) (5) between those that are near the carved surface and those issued from the intern areas; the more we move away from the surface, the more the concentration in iron and aluminum decreases. In other words, the selective spreading of exogenous components of the mineral crust of the surface observed on all the samples taken, and this migration’s variation from the carved surface to the heart of the cells’ web incorporated in the wood is confirmed.
Left to right. Microtexture surface portions P2 (MEB-ERD, x840). Details of fibrous tissue cells (MEB-ERD, x3570). EDS analysis spectra representative of the elemental composition of the natural mineral inclusions detected in the portions near the surface P2. Courtesy LAMOA Expertise.
Ceci montre que la sculpture a également subi une phase d’altération postérieure à son séjour en milieu aquatique, caractérisée par un délitement des parties les plus fragiles et des attaques locales de micro-organismes
-Marie-Pierre Etcheverry. LAMOA Expertise. Study of a Borneo wood sculpture. LAMOA 12-18 OA. 2008-
This process which consist in the development of a mineral deposit which is formed by clustering at the surface of a wooden statue immersed in a river’s silt rich in minerals (6) and the main components of which, iron, sulfur (S) and aluminum (Al), gradually migrate towards the heart of the wood’s cellular tissue, can take place only on a very large time-scale. We also observe that these superficial deposits have hardly penetrated the gaps and the open cracks (at a microscopic scale) present at the surface of the wood. This shows that the sculpture has undergone a second phase of alteration after its stay in an aquatic surrounding, and this is characterized by a delimitation of the more fragile areas and the local attacks of micro-organisms. It is probably the result of the “stress” undergone by the matter when this statue has emerged from the river. The brutal change of environment has provoked cracks and microscopic crevices perpendicular to the carved surface. Taken out from a damp environment and relatively stable temperature, the wood, with a spongy surface, has brutally dried under the effects of Borneo’s burning heat, probably during its carriage and because of its storing in a close village. The circle is complete.
Left to right. Microtextures surface portions of P1. (MEB-ERD x75, x85). We distinguish the destroyed walls (black arrows), the absences of material (orange arrow) and local attacks microorganisms (yellow arrows). Microtexture wood at the surface carved in sedimentary deposits area without (MEB-ERD x320). We can clearly see the many fissures and cracks perpendicular to the surface (yellow arrows). Courtesy LAMOA Expertise.
Wood an intact memory
All these observed characteristics, may they be macroscopic or microscopic, show that the object has undergone a natural aging process, in time, after its carving and consistent with its presumed agee.
-Marie-Pierre Etcheverry. LAMOA Expertise. Study of a Borneo wood sculpture. LAMOA 12-18 OA. 2008-
Each stage of the physical life of this Hampatong is visible, registered in the matter’s memory. From the worshiping area where men had raised it after having carved it, this statue, carrying stigmata from the equatorial climate’s hostility, tipped over by accident into the nearby river (mudflow or thrown into it vengefully, will we ever know?). Afterwards, little by little, it sank into the river, far away from the world where it was born. Over time, a silt shroud received it, covered, protected it during its sleep, accompanied by a greedy aquatic fauna of plankton. It slept for so long at its bottom that its mineral coat and its skin started to unite. Until a sudden storm, of an exceptional intensity, broke out on the surrounding mountains wrapped in a dark sky. A tempest with such vehemence that none of the forest’s inhabitant had seen since a long time. The devastating strength of its pouring rains modified the banks and shifted the silt-bancs of these rivers transformed into angry unruly streams. When the clouds were emptied and the sun appeared once more, men used again these water paths. Le Hampatong, awakened by the waters’ turmoil and the sounds of stones carted by the flow, emerged then once more into the world’s light. The choc is violent. Under the stifling heat, the wood contracts itself again, its water abandons it. Once more, it is naked under the scorching rays of a startling sunshine. It cracks, splinters. Ultimate wounds for a revival! Each step of this story is visible in the invisible. The wood has a memory which is undamaged. It has conserved and marked each of these steps, from its immersion to its emersion. This exploration of the matter is a trip in time, into the history of this piece of art which finds its conclusion in these scientific terms:
All these observed characteristics, may they be macroscopic or microscopic, show that the object has undergone a natural aging process, in time, after its carving and consistent with its presumed agee.
1. Le Figaro.fr /Valérie Saportas : L’art primitif n’est plus un monde à part (Primitive art is no longer a world appart) 12/09/2013.
2. Tribal Art Magazine, été 2013, Dr. Olivier Bobin & Dr. Armel Bouvier, Carbone 14, Datation de l’art tribal.(Carbon 14, dating tribal art).
3. Even though it seems to me unlikely, according to my field experience, to find in Borneo, a piece of timber dating of the 15th century, in such a state of conservation that it might be used for the work of a contemporary artist, the strangeness of this piece of art required a full investigation that leaves no doubt concerning its authenticity.
4. Term used in archeology to describe a timber that has stayed very long in an aquatic environment, running or standing water.
5. Aluminum is the chemical element with the atomic number 13, the symbol Al. It belongs to the group 13 of the periodic table as well as to the family of poor metals. The singular aluminum body is a ductile metal, of silver color, remarkable for its resistance against oxidation and of low density. It is the metal the most abundantly found in the earth’s crust and the third element the most abundant after oxygen and silicon; it represents an average of 8% of the material mass of the solid surface of our planet. Therefore, it is very natural to find it within the mineral components of a river in Borneo. source: wikipédia.
6. This phenomenon has been observed with an electronic microscope on a Buddha dating of the 6th / 7th century, which also came from a river in Borneo.