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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>David,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>In palaeontology, invertebrate fossils are routinely dusted with ammonium chloride (</span><span lang=EN>NH<sub>4</sub>Cl</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>) prior to photography to enhance contrast (often following blackening of the fossil), and in archaeology to eliminate reflection on shiny objects. The ammonium chloride is actually evaporated onto the specimen, which gives a very fine coating, much finer than you could achieve with any powder. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Ammonium chloride does not harm most types of objects and washes off easily with water, but will also evaporate from specimens/objects when left in a fume cupboard (no need for solvents in case of sensitive objects, just takes longer). Please let me know if you need guidance on the technique of applying ammonium chloride to the specimens. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>I have had some very good results photographing fossils using polarizers. Commercially available polarizers can be very expensive; have a look on eBay for polarizing film which is very cheap, available in all sorts of sizes, and you can quickly and easily build your own purpose-made polarizer for any camera/microscope. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Kind regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Christian <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>Christian Baars<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>Senior Preventive Conservator<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>National Museum Cardiff<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>Cathays Park<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>Cardiff CF10 4NP<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>029 2057 3302<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'><a href="mailto:christian.baars@museumwales.ac.uk"><span style='color:#0563C1'>christian.baars@museumwales.ac.uk</span></a> <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> nhcoll-l-bounces@mailman.yale.edu [mailto:nhcoll-l-bounces@mailman.yale.edu] <b>On Behalf Of </b>David Katz<br><b>Sent:</b> 19 August 2014 22:34<br><b>To:</b> nhcoll-l@mailman.yale.edu<br><b>Subject:</b> Re: [Nhcoll-l] Dusting/powdering skeletal elements prior to photographing<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><o:p> </o:p></p><div><p class=MsoNormal style='margin-left:36.0pt'>Rachel,<o:p></o:p></p><div><p class=MsoNormal style='margin-left:36.0pt'><br>That is what I expected. I'm working on developing a developing a photogrammetry protocol for making digital models of skeletal elements. Photogrammetry does a good job capturing bone shape when the bones have texture or topography, or preferably both. However, some bones, particularly cylindrically shaped bones that have been treated so that they are smooth and shiny, really offer photogrammetry software no noticeable topography from which to find overlapping points between a set of photographs. <o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:36.0pt'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:36.0pt'>One option was to try coating the bones. It seemed to me this wouldn't be workable for the vast majority of collections. Francisco suggested a polarizer, and I will look into this. I hadn't heard of it before, but I've now found some reports that polarizers and photogrammetry software work fine together. The final possibility that shiny long bones shouldn't be modeled using photogrammetry software.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:36.0pt'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:36.0pt'>... We'll see.<o:p></o:p></p></div></div><div><p class=MsoNormal style='mso-margin-top-alt:0cm;margin-right:0cm;margin-bottom:12.0pt;margin-left:36.0pt'><o:p> </o:p></p><div><p class=MsoNormal style='margin-left:36.0pt'>On Tue, Aug 19, 2014 at 12:50 PM, David Katz <<a href="mailto:dckatz@ucdavis.edu" target="_blank">dckatz@ucdavis.edu</a>> wrote:<o:p></o:p></p><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm'><div><p class=MsoNormal style='margin-left:36.0pt'>Hello,<o:p></o:p></p><div><p class=MsoNormal style='margin-left:36.0pt'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:36.0pt'>I've been told that in order to photograph elements that tend to reflect light strongly (teeth, highly polished bones), people sometimes coat them with a reflection-reducing powder. I was even told that baby-powder is often used.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:36.0pt'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:36.0pt'>Realistically, what do natural history curators permit? Specifically, are there types of powder coating that are particularly acceptable and non-destructive? Are standards different for recent vs. ancient skeletal materials?<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:36.0pt'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:36.0pt'>Thanks for you input.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:36.0pt'><span style='color:#888888'><br>David<br clear=all><o:p></o:p></span></p><div><p class=MsoNormal style='margin-left:36.0pt'><span style='color:#888888'><o:p> </o:p></span></p></div><p class=MsoNormal style='margin-left:36.0pt'><span style='color:#888888'>-- <br>David Katz<br>Doctoral Candidate<br>Department of Anthropology--Evolutionary Wing<br>University of California, Davis<br>Young Hall 204<o:p></o:p></span></p></div></div></blockquote></div><p class=MsoNormal style='margin-left:36.0pt'><br><br clear=all><o:p></o:p></p><div><p class=MsoNormal style='margin-left:36.0pt'><o:p> </o:p></p></div><p class=MsoNormal style='margin-left:36.0pt'>-- <br>David Katz<br>Doctoral Candidate<br>Department of Anthropology--Evolutionary Wing<br>University of California, Davis<br>Young Hall 204<o:p></o:p></p></div></div></body></html>