We can probably discard the conventional claim that a 3D plot
cannot be produced from a conventional photograph.
Shadowing is apparent in all of these images except perhaps the leftmost one. None of the other images would render a 3-d reproduction with a vp-8 or similar instrument.
Click on the photograph to enlarge it
How did I find all this? Colin Berry found it. He commented in Anticipating the Conference: Joseph Accetta on 14th Century Origins:
Try downloading this PowerPoint presentation from Joseph Accetta, David (he being the subject of a recent posting here, and one of STURP’s genuinely scientific, non-agenda driven, non grandstanding participants in my view).
(Unzip as if a pdf).
Go to the last few pages (approx 24/25). There you will see model spectroscopic (ir) studies not just with thermally-imprinted scorches, but also with linen that has been chemically dehydrated with 36% H2SO4 and even your invisible ink (lemon juice).
I’d be the first to admit there may be little to distinguish between an image produced by chemical as distinct from thermal dehydration (especially if chemical action was heat-assisted – see Luigi Garlaschelli’s model ‘frottage’ imprinting with acid-contaminated red iron oxide). It’s the vehicle for acid that is important (not too runny, not too viscous).
Some of us eagerly await details of what JA will say at St.Louis. Let’s hope it receives more attention than his meticulous and detailed studies to date.
Nuff said. I’m thinking of doing a post dedicated entirely to JA (he being my kind of scientist).
Nice find, Colin!