"Experiments are underway, which I shall report in real time, i.e. as a (web)log, which was the original meaning and intention of the “blog”, with new items being added to the top, rather bottom. It’s a little self-indulgent, I grant you, since it supposes that visitors come back for a second or third look. Neither is the end product terribly user-friendly to someone reading a reverse chronology, so to speak. But it’s a suitable format for a reporting a lot of bitty experiments in real time – as evidence that one is still busy and interested – and more user-friendly summaries of chief findings and conclusions can come later. I’ll call it : Weblog: further experiments to reproduce, albeit approximately, the Turin Shroud by non-supernatural means, e.g. by thermo-stencilling."
So here we go with the weblog, posted in reverse chronological order:
Experiment 2: Given that starch (from white flour") did not increase the charring of cotton by charcoal-mediated thermo-stencilling in Experiment 1, does further addition of glucose have an effect?
Here you see a 4g tablet of glucose (Boots, 92% glucose plus additives) ready to be added to the white flour suspension.
Conclusions (and discussion) so far:
Experiment 1: Does cotton char more quickly under a source of radiant heat if impregnated with a medieval source of "starch"?
What to use a source of starch? Potato starch is ruled out (Sir Walter Raleigh coming along much later). There is one reference I came across suggesting that starch for "starching" clothes in medieval times, and perhaps earlier, might have come from wheat bran. That would makle sense, given that bran has adhering flakes of starchy endosperm, i.e. white flour - which is not pure starch, needless to say, having some protein there as well. But i was not too worried about the latter, since protein would be necessary if the browning effect with impure starch depended on protein as well to generate Maillard type reaction products. So a level teaspoonful of white flour (self-raising, since no plain flour in cupboard) was added to 250 ml water, heated just to boiling with stirring, then cooled to room temperature. I then steeped half a cotton square in the cloudy suspension, allowed to drain, then dried over the radiator, and then applied my charcoal "paint" as previously described, i.e. a slurry of powdered barbecue charcoal. When the charcoal paint had dried, each black circle was held for 1 minute under a 60W ceiling spot. The charcoal was then washed out with tap water, and the strip of cloth dried and photographed.
Result after 1 minute of irradiation: the charred area was if anything lighter in the lower flour-impregnated half than the upper control (no flour). That admittedly qualitative result was confirmed a second time.
So despite starch being chemically more reactive than cellulose, there was no enhancement of charring by impregnating with starch. Indeed, there was possibly a little less charring. I am relieved in a way, since the fewer variables from hypothesised pre- treatments of ancient linen, e.g. during weaving, the better.
The next experiment will be to see whether a simple reducing sugar, e.g. glucose would affect the outcome. For that I decided to add glucose to the flour suspension, rather than test glucose alone (isolating variables one at a time can come later).