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INTRODUCTION
The precontact aboriginal rock paintings in the Canadian Precambrian Shield have a gritty residue. This implies that the pigments used were obtained from coloured sedimentary rocks, primarily those containing iron oxides. While this author was making pottery in 1983, a crushed yellow mineral rock was added to the clay. When fired, it produced an orange coloured pot. This occurrence was the inspiration for further investigations into pigments, bonding agents and paint.
People throughout the centuries have been fascinated by colours. This love of colour was first expressed with natural dyes and pigments. The American First Peoples' preference for red, black and yellow colours may be partially a result of the ease of availability of these pigments. Since pictographs are a means of expression and communication, they are very important to study in order to further archaeological and anthropological understanding.
BACKGROUND
A brief examination of some pigment samples from the archaeological record was conducted. David Meyer recovered a paint material sample during the analysis of the Niska site. This was later identified as hemaetite by x-ray diffraction analysis at the Saskatchewan Research Council (Mellinger 1985). Gil Watson (1985) recovered an ochre module at the Napao site. Grace Rajnovich (1983:35-36) recovered red and yellow ochre from the Spruce Point site in Ontario. In Stone Age Paintings, Selwyn Dewdney (1965:10) describes the paint he observed as red ochre, a loose term he uses for iron oxides. He describes the colours as ranging from a dull brick red to rusty orange and black.
It is obvious that iron oxides were used as pigments in one form or another, whether they be described as paint, ochre, hemaetite or limonite. Of these, only the paint material (hemaetite) from the Niska site was analysed chemically (Meyer 1985).
Some explanations of the chemical components of iron oxides will help elucidate the discussion. The word oxide by definition comes from the Greek word oxus, meaning acid. Oxides are composed of compounds of an element or mineral with oxygen. Larousse defines red ochre (ocre) as predominantly hemaetite, and yellow ochre as predominantly limonite (Librairie Larousse 1980).
Hemaetite comes from the Greek word hema, meaning blood; implying that the pigment is blood-red in colour. It is chemically known as ferric oxide (Fe2O3). Red ochre is an earthly or clay form of hemaetite which usually occurs as nodules. When found on the surface, it is usually brown in colour. Other varieties of iron oxide in the hemaetite category are ilmenite (FeTiO3) and magnetite (Fe3O4) (Quirt 1988).
Limonite is a general term used to describe all forms of hydrated iron oxide minerals (FeO(OH)), which occur as a natural clay or mineral, mostly in rock form. It includes goethite, akaganeite and lepidocrocite (Quirt 1988). Since these are also forms of iron oxides, limonite can be used as a substitute for hemaetite (Dr. Zenon Pohorecky, pers. comm.). Limestone is composed primarily of the mineral calcite (CaCO3), whereas dolomite [Ca, Mg (CO3)2] is the calcite (limestone) altered by magnesium bearing solutions. It is usually yellow or orange in colour. When parts of limestone are altered into dolomite the resulting mottled stone is commercially referred to as Tyndall stone.
EXPERIMENTAL APPROACH AND OBJECTIVES
1. Crushed and powdered mineral rocks will be used to determine if different colours can be obtained through varying applications of heat and oxygen. These reduced rocks will then be used as pigments for painting stone effigies.
2. To investigate natural materials suitable as bonding agents or fixers.
3. To test different combinations of pigments and fixers by painting some effigies on rocks and boulders.
4. To observe endurance to weathering and other natural processes.
METHODS
For the experiments, six mineral rocks yellow in colour and one yellow sample found in powdered form were obtained from excavated dugouts around Ponteix. Since doubt existed as to their being limonite, samples 4, 12 and 13 were sent to the Saskatchewan Research council for x-ray diffraction analysis. Samples 4 and 15 were predominantly dolomite (Ca, Mg(CO3)2) with trace goethite/akaganeite FeO(OH), which are forms of limonite, which in turn is a form of hemaetite. Sample 12, found in powdered form was predominantly yellow calcite (CaCO3) with moderate quartz, minor goethite and minor illite [clay mineral KAI2(Si3AIO10)(OH)2] (Quirt 1988).
PREPARATION
The samples 4, 12 and 15 were crushed and powdered with two cobblestones, or with a rolling pin when feasible. Hot melted tallow was added to the different pigments to the point of saturation. Tallow was obtained by melting the coarse surface fat from the meat of beef cattle.
BONDING AGENTS OR FIXERS
Bonding agents or fixers are used to adhere pigments to surfaces, to enhance colours or to extend the longevity of paintings. Iron oxide is used as a fixer due to its chemical properties. However, a mixer must be added to produce paint. Artists have experimented with every conceivable material from egg whites to blood. In this experiment the following bonders or fixers were used: tallow, bone marrow grease, water and clay plus urine and bile obtained from beef cattle.
Animal, bird and especially fish glues were considered for this study but were not used. Animal glues were traditionally obtained from hides, hooves or antlers. Glues were also obtained from bird bones and feet. Fish glue was obtained by boiling the bones and skin of non-oily fish. All these sources contain collagen, that constituent of connective tissue which yields gelatin upon boiling (Ian Brace, pers. comm.).
PAINT APPLICATION
Paint can be applied with the fingers, or by using a small brush or a small twig flattened at the end. The brush is the preferable method. Paint can be applied either as a paste when the tallow has cooled, or in a heated liquid form. Paint can be liquified by leaving the container exposed to the hot sun or by simply warming it with any heat source. Both the paste and liquid forms were tested in this experiment. The liquid form of paint is preferable.
Three variables were involved in the experiments: 1. Materials, 2. Heat and 3. Oxygen (plus oxygen and hydroxils where the (OH) factor is present). The materials were determined by x-ray diffraction analysis. The other variables were observed. The following paint colours were made and a brief description follows.
Red (1) -Usually made from oxides of iron such as hemaetite, which is ferric oxide Fe2O3, or forms of limonite FeO(OH). As a substitute, dolomite [Ca, Mg(CO3)2] containing a trace of limonite was used. The dolomite was taken from samples 4 and 15. Laboratory ferric oxide was also used as a basis for comparison. A sample of yellow muddy illite clay from Yoho National Park was used, which produces a red colour when heated. Back
Black (2) -Can be made by using nodules of manganese, which are difficult to find; therefore, black was the only pigment not obtained from sedimentary rocks. It was made by burning dry poplar wood and grinding the charcoal to a very fine dust-like powder. Back
White (3) -Made from limestone sources. Since local limestone can be ground to a powder, but tends to be yellowish, commercial lime was used. White pigment was also made using calcined bone and calcined shells from fresh water clams, but the result in both instances is a greyish white. Back
Yellow (4) -Made by using powdered dolomite obtained from local dugouts (the same used in the pottery sample and sample 15). When mixed with hot tallow, it turns yellow with an orange tint, but mixed with warm tallow it retains its original colour. When heated as a dry powder, brown and red are obtained. Back
Brown (5) -Made with kaolin obtained from deposits situated in the Wood Mountain area of Saskatchewan. It can be crushed and ground with ease. When heated, it turns brown, but when heated extensively and tallow is added, a black colour results through carbonisation. Kaolinite AI2(SiO5)(OH)4 is a common clay mineral. Back
Reddish Brown (6) -Made from reddish sand obtained from a sedimentary layer in deflation area on the NE 13 Twp.9 Rge. 12 W3rd. It was produced for observation, but not used as a pigment in the experiments. Back
Black (7) -This black colour was made by adding clay to the charcoal and hot tallow. The grey clay was obtained from a clay ball containing a high percentage of kaolin. When heated, it does not change colour. Clay added to any pigment thickens the paint and gives it a smooth texture; it also has adhesive qualities. Back
The above colours were produced in duplicate and triplicate to show they could be made on demand. Other colours made from dolomite and calcite samples, such as shades of brown and pink, were not used further in the experiments.
Different effigies were painted on various types of rocks and a boulder to demonstrate the method or pigment used. For display purposes, each effigy is labelled with the code number of the colours and pigment used. In this report the colours will be named.
Figure 1. Turtle Effigy (colour code number c-2-3-4-5) -This effigy was painted outdoors on a limestone boulder, the 9th day of September 1988 when the temperature was 18 C. The paint was applied in both solid and liquid form with a small brush. The next day, a 13mm slow rainfall did not alter the effigy. However, the next day a Richardson Ground Squirrel ate some of the paint. The effigy required some minor retouches. Later it was observed that the boulder had begun to absorb the tallow. This can be seen as the shadow-like areas on the margins of the effigy. By the 10th of November, the effigy was fixed and the hardening of the pigment was evident, despite the cold weather.
Figure 2. Stick-Man Effigy (c-2-3-4) -Red, black, white and yellow figures were brush painted in solid form on a block of red granite. As it was late in the season, it was feared the turtle effigy would not set before winter. Therefore, this and the remaining effigies were kept indoors at room temperature, and were placed outside in April 1989. Back
Figure 3. Stylized Bear-Paw Effigy (c-2-4) -Painted black and yellow in its solid form with a small brush on a slab of black granite with a grey surface. It was exposed to the noonday sun at room temperature to hasten the drying process as an observation. The melting tallow ran but the pigment held. Back
Figure 4. Sun Effigy (c-2-3-4) -Painted on a slab of layered granite using the colours black, white and yellow. Bile or gall obtained from the gall bladder of beef cattle was added to the pigment and tallow. It mixes well, hastens the drying process and serves as a bonding agent or fixer. The sun effigy was painted in fluid form with a small brush.
Figure 5. Moon-Faced Effigy (c-2-3-4-5) -Painted black, white, yellow and brown on a split cobble of siltstone. Urine obtained from the bladder of beef cattle was added to the tallow and pigment mixture. It mixes very well, hastens the drying process and is an excellent fixer or bonding agent. The moon-faced effigy was painted in fluid state with a small brush. Back
Figure 6. Crescent Moon Effigy (c-2-3) -Painted in fluid state with a small brush using the black and white colours. Clay was added to the tallow and pigment. It mixes very well, thickens the paint and hastens the drying process. Clay mixed with white gives a grey colour. The clay was used as a bonding agent and not as a pigment.
Figure 7. Deer Track Effigy (c-2) -Painted on a slab of grey granite using a mixture of charcoal, clay and water. It set up and dried quickly. Two weeks later, hot tallow was poured on the effigy, then it was placed upright to drain the excess tallow. The black colour became more vivid, but so was the colour of the slab. This effigy was applied in fluid state with a small brush.
Figure 8. Stick Woman Effigy (c-2) -Painted on a slab of grey granite using a mixture of charcoal, clay and water. It set and dried very fast, but the black is duller. The effigy was painted as a control for purposes of comparison with the Deer Track Effigy. Since clay can be mixed with water, it is expected that aging and weathering would be of short duration. It was painted in fluid state with a small brush.
Figure 9. Snakes Effigy -Painted on a slab of grey granite. The snake on the top was painted with a laboratory sample of ferrous oxide (hemaetite) mixed with bone marrow grease. The snake on the bottom was painted with dolomite from sample number 4 mixed with bone marrow grease. A slight difference in shades of the red colour resulted. The texture of bone marrow grease was similar to soft eleo-margarine and was an excellent mixer and bonding agent.
OBSERVATIONS
Pigments and colours produced from local samples of dolomite and calcite approximate those reported in the archaeological record. Since elements and forces in nature act as a blender, every mineral sedimentary rock sample is different, yet similar enough to be categorized. However, the trace elements they contain make every sample unique. Oxides of iron are very sensitive to heat and oxygen variations; this distinction makes it possible to obtain pigments of different colours from a given sample. Of the many samples of dolomite used in the experiments, only one was found that did not contain traces of any form of oxides of iron. It did not change colour when heated.
The experiments have shown that urine is the best mixer and bonding agent when used with tallow. Otherwise, bone marrow grease is the best. It was stated earlier that iron oxides, by their composition, may be fixers. Yet it remains to be shown if dolomite and calcite will react in the same manner, even though only trace elements of limonite are present.
The Turtle Effigy was still in excellent condition after exposure to the weather for over a year. It survived -42 C for 4 days, 110 mm of rain in two days and 38 C for 5 days. It was unprotected from the weather and faces the afternoon sun. The other effigies were exposed to the weather since April and survived in good condition; except the Stick woman effigy, which washed away with the first rains as was expected.
DISCUSSION
The fact that dolomite and calcite used in the experiments produced colours similar to haematite can be explained by the trace limonite in the samples. It is documented by Rice (1987:335) that a one percent solution of iron oxide will produce a yellowish colour, 1.5 to 3 per cent a light brown or orange colour and over 3 per cent a red colour; depending on the degree of heat applied and the amount of oxygen present.
Likewise, red paint used as a slip in pottery manufacture is derived from illite clay mineral (Rice 1987). When the dolomite samples 4 and 15 were heated to a brown colour then quickly cooled, it turned a duller brick red than hemaetite. Hemaetite heated the same way does not change colour. The colours of all the samples have not changed in the last year.
The gritty residue on rock paintings implies that a thick coat of pigment was applied, but the bonding agent or fixer is no longer present. It was stated earlier that oxides are acids and that oxide pigments are the true fixers or bonding agents. Therefore, urine (which is diluted uric acid) would serve the same purpose. The use of fat and bone marrow grease, or glues obtained from bird, fish or animal sources would then serve only as temporary bonding agents, fixers and mixers. Meanwhile, the chemical reaction between the acid pigment and the rock face takes place, and improves the durability of the rock paintings.
A dated pictograph does exist in the historic record. Before returning from his trip across Canada, Alexander MacKenzie made some paint by mixing powdered red rock with melted grease. On a large rock where the Bella Coola River flows into the sea, he painted these words: Alex MacKenzie from Canada by the land the 22nd of July 1793 etc (Scott 1943).
Pictographs are found mostly in the Canadian Precambrian Shield where iron and its oxides occur readily in nature. As most pictographs are painted on rock walls, they provide protection from the elements and animals, especially when first painted. If the pictographs were interpretations of dreams, then there were no fears of destruction by the artist's contemporaries (Dewdney 1965:14).
CONCLUSIONS
The experiments have shown that dolomite and calcite may have been used to paint pictographs as an alternative to hemaetite, where the colours yellow and orange are concerned, or when a darker or duller red is evident. It has been shown that the Turtle Effigy has survived weathering for one year, the others for six months. Since there are no known ways to artificially speed up the aging process as a basis for comparison, this part of the experiments must, of necessity, remain in the realm of speculation. However, the "Mackenzie Pictograph" is a good indicator of what can be expected for the experimental and all other pictographs. It is still impossible to determine which is the best bonding agent, but the colours Mackenzie left lasted some 150 years.
ACKNOWLEDGEMENTS
Special thanks are extended to Ian Brace for reading the original draft of this paper, for suggesting a suitable format and for his general advice. Thanks also to Bob St. Cyr for making transparencies and photos of the experiments. His help came at an opportune moment.
EDITORS NOTE
Several years had elapsed between the submission of this article until this publication. Henri Liboiron has kindly supplied the following update to his experiments:
All effigies were exposed to the elements for one year, except the Turtle Effigy. After one year they were brought indoors because it was feared that bird droppings would affect the results of the experiments. All are in the condition stated in the paper.
The Turtle Effigy has been exposed to the elements since October 1989. The pigment containing iron oxide is still in excellent condition. The lime pigments have withstood weathering in good condition. However, the black pigment made from charcoal has completely washed away. As for the yellow pigment, it is slightly faded.
REFERENCES CITED
Dewdney, Selwyn. Stone Age Paintings, Winnipeg, Department of Mines and Natural Resources, 1965.
Librairie Larousse. Petite Larousse en Couleurs. 1ère ed., Paris, 1980.
Mellinger, Michel. X-ray diffraction analysis of hematite sample, Regina, Saskatchewan Research Council, 1985 .
Meyer, David, Excavations at the Niska Site, Ottawa, Canadian Journal of Archaeology, 1985.
Quirt, David. Saskatchewan Research Council, Saskatoon, 1988.
Rajnovich, Grace. T he Spruce Point Site, Toronto, Ontario Ministry of Citizenship and Culture, 1983.
Rice, Prudence. Pottery Analysis, Chicago, University of Chicago Press, 1987.
Scott, Joseph. The Story of our Prairie Provinces, Toronto, Ontario , M. Dent and Sons (Canada) Ltd 1943.
Watson, Gil. The Napao Site. Test excavation , first draft,, Regina, Royal Saskatchewan Museum. 1985.
Reference:
Liboiron, Henry. Experiments in Aboriginal Pigments and Paints, Saskatchewan Archaeology, vol. 14, (1993), pp. 34-42.