Thibault’s Principle: “No scorch produced by pressing a heated template onto linen can hope to match the subtlety of the Shroud image, either at the macroscopic or microscopic level.”
I suppose it should be called Heimburger’s Principle. It’s Thibault Heimburger MD. But let’s keep this informal if we can.
In fact, he didn’t state it in those precise words, but it is implicit in everything he said, and probably what John Jackson said, whom he quotes. Here’s a flavour:
“In other words, even with a less than 1 millimeter high relief, either the relief has the right color and the neighboring areas have no color either the neighboring areas have the right color and the relief is much too colored.”
And as I say: Thibault then looks to John Jackson for support with this:
“This problem of contrast has already been discovered by Jackson.”
I have briefly discussed Jackson’s work on a previous occasion, and declared my admiration for what he achieved, whilst having reservations on a number of grounds. But it is not his work that is in the frame today, but Thibault’s. Today I concentrate on the macroscopic aspects of the Thibault Principle (the microscopic ones will follow later),
They say a picture is worth a thousand words. Well, here’s a few pictures that convey why I think the Thibault Principle as enunciated above is irrelevant to the Shroud image, due to use of an inappropriate template that by no stretch of the imagination could be described as ‘bas-relief’ relevant to the human form. Yes, I’m all in favour of simplified models that hone down to essentials, eliminating as much superfluous detail as possible, but a flat chunk of metal that is virtually right angles and slots is simply not ‘fit-for-purpose’. Sorry to have to be so frank, Thibault, but “nul points” re your choice of template, and nul points to any and all conclusions based on that choice,
Now this is what I call a proper template – a BAS-RELIEF – with a complex mix of vertical and horizontal planes, many of them neither completely one or the other, ie. the metal makes contact with linen at a whole range of angles between 0 and 90 degrees to the normal.
More to come, but I hope folk will see that as far as the macroscopic level is concerned , Thibault’s Principle has failed to put in an appearance in my experiments, and would not have in his either if he had made a sensible and appropriate choice of template. Given that he cites Jackson’s work, and looks to him for support, then why did he not take a leaf from Jackson’s book and choose a proper BAS-RELIEF template?
The trickier party of responding to Thibault is yet to come, i.e. in addressing the comparison between the Shroud image and model scorches at the microscopic level. All I would say for the moment is that one is not comparing like with like, age-wise, and allowance must be made in one case for wear and tear. The Shroud image probably looked very different centuries ago – both to the unaided eye and under the microscope.
I shall now take a break for a day or two, while, as I say, reserving the right to edit this somewhat hastily-assembled post…
Postscript: the crucial aspect re templates and imprinting is that subtle factor of frontal v. vertical plane of presentation. Imagine for a moment you had some linen spread over a sand bed, or some other underlay designed to get best contact between heated template and linen. (I’ve switched from using sand to a few layers of thick fabric). Imagine one had a small cube or sphere of soft metal that could be hammered into any shape one desired.
One could either have maximum area of initial contact, or minimum area of initial contact. If it were the first of those one would hammer out the metal to get a thin but rigid sheet, and then press it into the linen. But there would be a lot of resistance, and rather good imprinting (scorching) all over if the metal were hot. Suppose one presented it edge on – in other words the thin edge of the metal plate. Then there is now something like a blade that allows one to get a lot of contact laterally in terms of area (not on the leading edge, with its small area) but at a tangential angle, close to the parallel, that will not be conducive to scorching EXCEPT for the tiny area of the leading edge. Same amount of metal, but high contact pressure and all-over scorching in one instance, and low contact pressure (per unit area) and little scorching in the other (except for that intensely scorched leading edge).
In practice, any given object is somewhere intermediate between those two extremes. Thibault’s template is at one extreme, with a lot of contact pressure, whereas a bas relief is intermediate. There is the added subtlety that Thibault’s template is a pair of planes, separated by a small shelf, and while the distance of vertical separation is small, a mere 1mm in his raised relief template, it is enough to give a large difference in contact pressure and scorching of the first plane making contact with the linen and the second. A bas relief on the other hand penetrates more deeply, with its greater proportion of vertical to frontal plane, and thus one sees less of that “contrast problem” on which he places so much emphasis (excessive emphasis in my view).
Afterthought: Wed 24 October Re UNDERLAY
Early in my own studies I reported the importance of underlay for good thermal imprinting, alluded to briefly above. The crucial factor was to imprint vertically into the linen, the latter being spread initially over dry or dampish sand. Later I found a folded-up pad of thick floor cloth to be effective in getting good detailed imprints. It’s not difficult to see why – there has to be a resistance to “push” the linen up into the holllows and recesses of the bas relief to get maximal metal-linen contact, capturing as much detail.
But when you look closely at Thibault’s reports of each experiment, one gets the impression that he was slow to appreciate the importance of underlay, at least initially. In his first experiment he seems to be pressing linen DOWN onto hot metal, presumably gripping it at the sides and ‘stretching it over’. That would explain why the sunk relief portion in the centre was so poorly imaged. Later he talks about using a “firm surface”, suggesting that he had by then adopted my vertical presentation, using the template as one would a date-stamp, and later still there is a reference to a “soft pillow”.
I cannot stress too strongly the importance of underlay. Some of the “excessive contrast” that Thibault’s paper claims makes scorching a non-starter where medieval forgery is concerned can be explained simply by his failure to provide an underlay with the right combination of “give” and resistance, ensuring maximum contact between template and linen.
Update: Quote of the day from “Andy Weiss” on The Other Site: