Tuesday, January 3, 2012

Tom Chivers - re that Turin Shroud: you are the first (possibly second) person to be thermo-stencilled ...

"Tom Chivers is the Telegraph's assistant comment editor. He writes on science, culture and anything that crosses his mind."

 That's what it says at the top of Tom Chivers' Telegraph blogsite - he of the commendable breadth of interest, taking in, unusually for this day and age, a range of scientific topics (and much else besides).

But he was not always called that. In fact I once pulled his leg re his previous somewhat grandiose title ("Strategic Events Editor) - how to win friends, ha ha.... ;-)

Maybe Tom ran out of strategic events to report. Well, here's a possible candidate, says I immodestly - a simple procedure that one CAN safely try at home and which might, and may, just may, have been the technology by which the Shroud of Turin was produced in the 14th century as a fake "holy relic".

Here is a series of pictures that should tell the story without needing a lot of words.

Photograph, "shroud cloth", charcoal

Place photograph under fabric, place on glass sheet, illuminate from beneath

Completed charcoal tracing

After radiating from a 60W spot light for about 5-10 mins, viewed from reverse side before washing - selective scorching apparent.


 After washing out the charcoal and drying.  OK, so the image is faint (but then so is the Turin Shroud's!)

Hiya Tom. You're not looking your usual self today... Feeling a bit browned off?

The next step is to improve the image intensity. I've just made some charcoal paint, using a slurry of powdered charcoal in water with a dash of wetting agent. It paints beautifully onto cloth. The next step is to grill under a source of radiant heat, and wash out the charcoal "stencil".

(Oops. I had meant to add this to the end of the next post, the one describing use of charcoal paint. Never mind.)   Next experiment? It is said that the image is not formed on the cellulose fibres, but on a surface coating of starch, the latter having been used as an aid to weaving:


Evidence for this is that the image can apparently be stripped off physically with adhesive tape (which is certainly not the case for scorched cotton) or reduced chemically with diimide, N2H2.

So the next step is to repeat the experiments with a starch-coated fabric. It's my guess that scorching will occur more readily with starch, which is chemically more reactive alpha-linked glucan, than with cellulose (beta-linked glucan), the latter having more extensive crystallinity due to  multiple intermolecular hydrogen bonding interactions. If scorching can be achieved quickly, then it may indeed be possible to strip off a superficial scorched layer from underlying cellulose, simulating more closely the characetristics of the Shroud. I shall have to think of an authentic (historically credible) source of starch. It certainly won't be potato starch!


Anonymous said...

I don't think its much like the original but it looks cool!!

sciencebod said...

Maybe not. But it was done as a quick line drawing with charcoal. I'm sure that if the exercise were to be repeated with a charcoal "paint", carefully applied to get a more artistic effect with light and shade, then the end result would be more persuasive. I may have another go in due course, but am preoccupied with other matters at the moment. If anyone wants to have a go, and gets a good result, then feel free to do so, and I'll display the piccy here if they care to email it.