#C: Making Cements with Plant Extracts

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Fabrication of stone objects, by geopolymeric synthesis, in the pre-incan Huanka civilization (Peru)

Joseph DAVIDOVITS and Francisco ALIAGA
Abstract of a paper presented at the 21st International Symposium for Archaeometry, Brookhaven National Laboratory, New York, USA, 1981 (page 21).

It is now agreed, that the TIHUANACO civilisation is modeled on the pre-incan HUANKA civilisation revealed by an extraordinary skill in fabricating objects in stone. A recent ethnological discovery shows that some witch-doctors in the HUANKA tradition, use no tools to make their little stone objects, but still use a chemical dissolution of the stone material by plant extracts. The starting stone material (silicate or silico-aluminate) is dissolved by the organic extracts, and the viscous slurry is then poured into a mould where it hardens. This technique, when mastered, allows a sort of cement to be made by dissolving rocks; statues which could have been made by the technique of the pre-incan HUANKA, by dissolution followed by geopolymeric agglomeration, are found to contain Ca-oxalate in the stone.

The disaggregation of stone materials with organic acids from plant extracts, an ancient and universal technique

Joseph DAVIDOVITS, A. BONETT and A.M. MARIOTTE
Proceedings of the 22nd Symposium on Archaeometry, University of Bradford, Bradford, U.K. March 30th – April 3rd 1982. Pages 205 – 212.

At the XXI Archaeometry Symposium we presented the hypothesis that the large stones in precolumbian monuments were artificial, having been agglomerated with a binder obtained by disaggregating certain rocks (in agreement with local legend and tradition). We present here the first results on plant extracts on the dissolution or disaggregation of calcium carbonate containing rocks (Bio-tooling action). The feasibility of chemically working calcium carbonate with various carboxylic acids found in plants (acetic, oxalic and citric acid) has been studied. Maximum bio-tooling action is obtained with a solution containing:

  • vinegar (1 M) (acetic acid)
  • oxalic acid (0.9 M)
  • citric acid (0.78 M)

The great surprise was actually to discover very ancient references to their use since Neolithic times for working materials which are very hard but easily attacked by acids, such as chalk. Thus, a bas-relief from the tomb of Mera, at SAQQARAH (VI dynasty, 3Millenium B.C., Egypt) (Fig.6 ) shows the hollowing out of “Egyptian alabaster” (CaCO3) vases by a liquid contained in a water skin or bladder. An experiment of interest was to compare the “bio-tooling” technique with the shaping of a hole using steel tool and the quartz sand technique recommended by prehistorians. The hole resulting from sand abrasion has rough walls, whereas bio-tooling gives a smooth finish.

The precolumbian farmers were quite capable of producing large quantities of acids from such common plants in their region as:

  • fruits, potatoes, maize, rhubarb, rumex, agave americana, opuntia, ficus indica, oxalis pubescens

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