Archaeological interest in burned bone has centered upon four topics:Determining whether or not bone has come into contact with fireEstimating the maximum temperature attained by a fireUsing changes in superficial bone color and fracture patterns to estimate the condition of bone at the time it was exposed to fireDtermining the degree to which the original dimensions of the element have been altered by burning
The process of burning bone is essentially a process of dehydration and recrystallization. Bone will undergo dehydration and be subjected to the corresponding changes. Specifically, the elimination of water, and the subsequent consumption of the organic portion of bone and the microstructural alterations to the hard matrix of bone results in a color change, as well as splitting and warping.
Oxygen availability has a profound effect on the color of cremated bones exposed to the same cremation temperaturesAs the duration of cremation increases, the influence of oxygen availability on bone color gradually diminishes
Shipman et al. (1984) established a correlation between colour and temperature. However, color changes may be due to bone interaction with environmental materials. After burial, bone may be altered and may change color as a result of soil composition, sediment pH, temperature or moisture, and the changes may occur in the bone tissue as ionic substitution.
Black bones have been discovered in the Northern Coast Cave. Two areas of the cave have exhibited signs of burning. Both these sites contain infant remains. Using previous research, the black color of the bones indicates that the bones may be carbonized bone due to burning in oxygen starved context (Herrmann 1970) or simply that the temperatures reached by the cremation fires were between 525 to 645 degrees Celsius (Shipman et al. 1984).The remains found seem to indicate that infant remains were subject to cremation in the Taliotic culture.
In the Cueva de la Costa Norte” (“Northern coast cave”) some of the skeletal remains are a blue/green color as shown here. This indicates that the bones were burned with bronze. Bronze turns a greenish color when it oxidizes. Not only is oxygen necessary for cremation fires, but also the bones may have been exposed to open air for a period of time before they were covered.
Cremation presentation Marcelle La Croix
a presentation on cremated remains By: Marcelle LaCroix Session 6 Presentation 25 August 2012
Determining if bone has come into contact with fire Estimating the maximum temperature of the fire Using changes in color and fracture patterns to estimate the condition of bone Determing the degree to alteration by burning
Oxygen availability Duration of cremation Materials used
Stage Temperature Range Color1 < 285°C Neutral white, pale yellow, yellow2 285 - 525° C Reddish brown, very dark grey-brown, neutral dark grey, reddish-yellow3 525 – 645°C Neutral black with some blue and reddish- yellow4 645-940°C Neutral white with light blue-grey and light grey5 940+ °C Neutral white with some medium grey amd reddish-yellow
Color Interpretation ReferencesBrown Hemoglobin and/or soil Gejvall 1969; Lisowski discoloration 1968Black Carbonized bone due to Herrmann 1970 burning in oxygen starved contextGray-blue, gray white Pyrolizaed organic Dokládal 1969, 1970; components; calcination; Mayne Correia 1997 complete loss of organic portion and fusion of bone saltsOther colors: green, Burning in the presence Dunlop 1978; Gejvallyellow, pink and red of metals including 1969; Lisowski 1968 copper, bronze or iron
copper = pink color iron = green color zinc = yellow color bronze = blue/green color
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