|The interpretation of that mass of information was down to Professor of Chemistry, Professor Ralph Raphael and myself. No two fragments showed the same results, even different readings were observed in different parts of the same fragment. Nevertheless, all the same bunch of elements appeared in all the fragments, just in different proportions. The layers were very thick, average 30 - l00 microns. Clearly deliberately applied, sometimes in layers, and adhered strongly to the wood.
|EDAX Spectra showing elements present in the ground layer|
|The first and obvious question that was asked was, could this be stuff left after smoothing the wood with something abrasive like pumice. There is simply no way that a layer of pumice could have been left l00 microns thick, or even 3 microns, besides which the analysis of pumice is quite different.
Without the benefit of crystalographic analysis, Prof. Raphael considered that the end product was basically Calcium Silicate with a soupçon of other salts. Jim Woodhouse and Claire Barlow tend to refer to it as either stuff or l7th century polyfiller. Whatever label it is given, the evidence shows that it is there and in quite large quantities and that just about everybody in Italy, l6th, l7th and l8th centuries was doing it.
Even across diciplines. A materials scientist at Rome Univ. was asked how the Roman statues had survived the rigours all these centuries. He discovered that many of them were also covered with a layer of similar constituents..
Mineral Ground paper Page 2