Dear Dan,
[Your friend]’s question is legitimate, like almost all questions, but it denotes a not updated knowledge of published scientific data and results obtained in the last ten years. We answered [your friend]’s question in our paper published in Applied Optics in 2012, see Superficial and Shroud-like coloration of linen by short laser pulses in the vacuum ultraviolet.
More recently, we were even more explicit, see reference [9] in the paper Shroud like coloration of linen, conservation measures and perception of patterns onto the Shroud of Turin.
In short, the sentences of Rogers were triggered by negative experimental results of excimer laser irradiations on linen (as well as of particle irradiations). Rogers wrote "Experiments we did with pulsed ultraviolet lasers on linen resulted in ablation and destructive shock waves. Samples often were converted into a little amorphous powder and gas”. (Testing the Jackson “Theory” of Image Formation)
Moreover, he wrote “Very intense, 50-ns-long bursts of UV ablated the cloth surface, and the samples were reduced to a cloud of very fine particles. We could not get a color with a flash of light.” (Scientific Method Applied to the Shroud of Turin: A Review)
Few years later, in 2006 we have experimentally shown the above Rogers’ statements are simply not true. We obtained a superficial coloration of linen by UV laser beam without destroying the linen, nor altering linen’s structure. Does it means Rogers’ results were wrong? No, because we experienced the same Rogers’ failure when using longer than 50-ns laser pulsewidth. Rogers and his coworkers just used a too long laser pulsewidth, and the wrong combination of intensity/fluence/ number of shots to obtain a Shroud-like coloration. Details on why it happened are given in Shroud like coloration of linen, conservation measures and perception of patterns onto the Shroud of Turin.
This is normal in science, one performs an experiment with negative results, and later another one finds the good combination of parameters to achieve the desired results. I am sure a honest scientist as Rogers was, would have recognized his "overestimation" of radiation results.
And this is the main reason why a wise scientist never writes his/her results are the "definitive proof" or "provide conclusive evidence" of something. Every result is obtained in good faith (bona fide) until another scientist proves otherwise. Unfortunately not all scientists are wise, see e.g. the conclusions in the Nature’ paper on Shroud radiodatation.
Hope this may clarify the issue, ….
All the best
Paolo
Thanks, Paolo.
*Editing note: To better fit in this blog, I took the liberty of replacing long http-ish links with the actual titles of papers and made the titles linkable. Most browsers will show you the original link if you hold your mouse-cursor over the title. I also replaced my friends name in the letter since it has not been revealed here.