It was pointed out to the late collector and his consultants a number of years ago that the paint between and encircling the two heads reveals a broad cracking pattern, sometimes known as 'alligatoring'; and that this is very uncommon in 15th /16th century paintings and very common in early 19th century works. Because of this, steps were taken to have this area of paint specifically tested forensically – in addition to all other areas of the painting. Whereas SEM analysis had revealed that the whole of the remainder of the painting is built up in a series of particularly thin layers, the paint in this area around the heads was found to be entirely discrete. The Scientific Report of Henry Bland, Consulting Forensic Scientist, dated 2nd August 1999 stated:
"Sample 5 from between the heads appeared to be thickly applied, cream in colour and was badly cracked. Under the microscope this paint differed from all other samples examined. It was discrete and showed no evidence of any other paint layers; even the presence of size could not be confirmed".
His Report Opinion concluded:
"The paint from between the heads which looks somewhat crude to the naked eye on the Tondo itself, appears dissimilar to any of the paint in its underlayers and may well be a later addition. I am not qualified to comment on artistic techniques but I would not be surprised to discover the Tondo had been 'restored' and or cleaned and repainted, perhaps somewhat inexpertly, at some time during its existence".
A second type of craquelure which clearly affects the painting is horizontal and vertical parallel cracking. Page 55 of Dr Murdoch Lothian's PhD thesis states:
"There is regular horizontal and vertical parallel cracking over most of the surface of the Tondo suggesting that either (a) the canvas has been stretched, or restretched, at some time after the paint has dried, or (b) the canvas has been rolled in both directions, and probably, at some time, been rolled in the wrong way, i.e. with the painted surface inwards". (Lothian states that rolling was a convenient means of transportation for paintings on canvas).
Since the greatest incidence of horizontal parallel cracking is at the bottom of the canvas, perhaps it had been most frequently rolled up from bottom to top, with the bottom as the tightest part of the roll.
The third type of craquelure affecting the whole of the Tondo is "….overall, a fine irregular network of cracking" (Lothian thesis, page 143).
The trustees have been advised by conservators who have worked on the Tondo and other experts who have examined the painting that it is this fine, irregular cracking that one would expect to find in the surface of a painting of antiquity.
The de Brécy Trust