Experimentally produced glass compared with that occurring at The Torr, NW Scotland, UK: vitrification through biotite melting

Friend, C. R. L.; Charnley, Norman; Clyne, H.; Dye, J.

doi:10.1016/j.jas.2008.06.022

Cited by 12 publications

(16 citation statements)

References 13 publications

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“…1 we show the evolution of the experimental materials as they are heated to temperatures anticipated for the generation of vitrified textures found in forts1314. Using differential scanning calorimetry, we show that bulk melting temperatures may vary significantly from one lithology to the next (1293–1350 K – Lanhélin granodiorite and 1200–1340 K – Darley Dale sandstone determined by the onset of the partial melting endotherm; Fig.…”

Section: Results: the Evolving Properties Of Vitrified Enclosure Wallsmentioning

confidence: 85%

“…To explore the first-order variability in μ , we have employed both bulk- and glass-compositional data from the walls of 45 Iron Age forts across Europe (including experimentally produced glass from partial-melts of protoliths)1341214 and reference material compositions of Moine assemblages from Scotland31 together with a multicomponent silicate liquid viscosity model23 in order to obtain the composition-dependence of the fragility m of the liquid viscosity. The fragility is a measure of the temperature-dependence of the viscosity in the high viscosity region (close to the glass transition of the liquid intersected at a cooling rate of 5 K.min −1 ) and is given by23…”

Section: Results: the Evolving Properties Of Vitrified Enclosure Wallsmentioning

confidence: 99%

“…Previous work has shown that vitrification of Iron Age enclosure walls occurred during prolonged episodes of heating to peak temperatures of 1270–1570 K4121314 for durations >5 hours13. Under such conditions, most of the rock types from which such prehistoric walls were built undergo partial or complete melting12, and have yielded upon cooling, a glass, or the devitrified products thereof.…”

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confidence: 99%

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Local geology controlled the feasibility of vitrifying Iron Age buildings

Wadsworth

Heap

Damby

et al. 2017

Sci Rep

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During European prehistory, hilltop enclosures made from polydisperse particle-and-block stone walling were exposed to temperatures sufficient to partially melt the constituent stonework, leading to the preservation of glassy walls called ‘vitrified forts’. During vitrification, the granular wall rocks partially melt, sinter viscously and densify, reducing inter-particle porosity. This process is strongly dependent on the solidus temperature, the particle sizes, the temperature-dependence of the viscosity of the evolving liquid phase, as well as the distribution and longevity of heat. Examination of the sintering behaviour of 45 European examples reveals that it is the raw building material that governs the vitrification efficiency. As Iron Age forts were commonly constructed from local stone, we conclude that local geology directly influenced the degree to which buildings were vitrified in the Iron Age. Additionally, we find that vitrification is accompanied by a bulk material strengthening of the aggregates of small sizes, and a partial weakening of larger blocks. We discuss these findings in the context of the debate surrounding the motive of the wall-builders. We conclude that if wall stability by bulk strengthening was the desired effect, then vitrification represents an Iron Age technology that failed to be effective in regions of refractory local geology.

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Section: Results: the Evolving Properties Of Vitrified Enclosure Wallsmentioning

confidence: 85%

Section: Results: the Evolving Properties Of Vitrified Enclosure Wallsmentioning

confidence: 99%

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confidence: 99%

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Local geology controlled the feasibility of vitrifying Iron Age buildings

Wadsworth

Heap

Damby

et al. 2017

Sci Rep

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“…[43] The temperature needed for partial melting of typical stone material in a vitrified fort is 900 -1100 ºC [39][40][41][44][45][46]. Much of the heat required is consumed for the melting.…”

Section: Heat Quality Considerationsmentioning

confidence: 99%

On the possibility of using vitrified forts as anthropogenic analogues for assessment of long-term behaviour of vitrified waste

Sjöblom

Ecke

Brännvall

2012

WIT Transactions on Ecology and the Environment

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An information survey was conducted in the areas of natural analogues, vitrified forts, combustion technology and vitrified waste. The main purpose was to identify if vitrified stone material in hillforts might be used as anthropogenic analogues for glass containing waste. Such comparisons are needed in order for predictions to be made regarding the long-term integrity of the waste forms. The scope was to compare the chemistry as well as the processes used for the generation of the glasses.It was found that the vitrified forts contain glass material with wide variations in composition of the major elements. They cover and exceed those in the glasses made of waste with only the exception of phosphorus. Natural glasses as well as archaeological glasses show much narrower ranges of compositions, and they do not coincide with those of the glasses containing waste.Quality of heat analyses indicated that it is likely that the stone material in the forts was melted for the purpose of obtaining long-lasting structures. This narrows the range of possible processes used, and facilitates reconstruction of the ancient methods by means of testing. This, in turn, provides possibilities of comparison between ancient and modern methods, which can then be used as a basis for validation of the use of the analogue.

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“…Conventional studies claim that vitrification was the result of destruction towards the end of occupation, whereas others suggest that the melting might be constructional (cf. Friend et al, 2008 for a comprehensive review). In the case of Tilmen, such features are likely to be related to traumatic events -either the fire of a single building or enemy destructions of the whole site -with fires, which destroyed the wood structures and burned natural stones.…”

Section: Introductionmentioning

confidence: 99%