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Message: <blockquote data-quote="Umbran" data-source="post: 1995428" data-attributes="member: 177">Having poked around a bit, I've found something even better, insofar is it is more fun to think about <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f642.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":)" title="Smile    :)"  data-smilie="1"data-shortname=":)" />Chemicals leave residues... unless you wash them out!  Try this one - while modern photography and "photonegatives" weren't known 700 years ago, some basic optics were known even to Aristotle.  It is known that Leonardo da Vinci knew the theory and workings of the camera obscura - essentially a pinhole camera.  Drawings of such are in his papers.  So the man knew how to throw an image onto a surface.Take a large cloth.  Paint it all over with the appropriate mild oxidant solution - yes chemistry was lousy then, but you don't need it to be good, by today's standards, in order to work.  Throw an image on the cloth using a camera obscura.  The light energizes the oxidant, burning the image on the cloth.  You then launder the cloth, washing out the oxidant, but leaving the image.   Oh, I'm quite well acquainted with the "Too cool to be true" rule.  It holds for the hard sciences as well.  We don't have aliens and flying cars because they'd be just too cool <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f642.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":)" title="Smile    :)"  data-smilie="1"data-shortname=":)" />Why?  Well, try this...In Da Vinci's time, in Italy, having religious relics gave a family considerable clout.  The Shroud was owned by the Savoy family.  The Savoys had aspirations (and they achieved them, eventually becoming the royal family of Italy).  The Savoys had a shroud since back in 1464 or so.  But they didn't show it off much, and at least one local bishop declared it a fraud, and the Pope had to shut him up.So, the Savoys are climbers, and want a nice shroud to exhibit.  The Duke of Savoy had a son-in-law named Giuliano de Medici.  Da Vinci worked for Guiliano, among others.  Surely, the Savoys could afford to pay Da Vinci a considerable sum for the work.  If that failed, Da Vinci was a vegetarian and practitioner of certain sexual practices the church frowned upon.  If need be, Da Vinci could be pressured into making the thing.  Interestingly, in 1494, the Savoys switched from showing the shroud every decade or two to showing it every few years.  Perhaps they were presented with a shroud that was better to look at?</blockquote>

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