[Nhcoll-l] Dusting/powdering skeletal elements prior to photographing

Wed Aug 20 12:32:16 EDT 2014

Does anyone have a suggestion on a supplier for the glass receptacle to
sublimate the NH4Cl?  We've been wanting to get our ammonium chloride set
up operational again for photographing vertebrate fossils. It was
recommended that we have the glass receptacle custom made by a local glass
blower.  Any other suggestions?

In the interim, one of our curator's has used Spotcheck Developer SKD-S2
manufactured by Magnaflux (see portion of MSDS copied below).  It's a talc
spray used for spot checking welds.  I wouldn't recommend the product since
it can be difficult to remove (especially if a fossil has been
consolidated) and it can be tricky to achieve a light, even coating that
doesn't obscure the morphology.  A dry rag with water or ethanol has been
the most effective at removing the residue after photography. Nonetheless,
it is quick and easy to apply.

SPOTCHECK® DEVELOPER SKD-S2
1. IDENTIFICATION
Company: MAGNAFLUX
Address: 3624 West Lake Avenue, Glenview, Illinois 60026
Telephone No.: 847-657-5300 (Off-Hour Emergency Number - CHEMTREC -
1-800-424-9300).
Product Use: Penetrant inspection developer
Packages: 1 gallon can, 5 gallon pail, 55 gallon drum, aerosol
NFPA Rating: Health 1, Flammability 3, (aerosol 4), Reactivity 0
PIN (Canada): UN 1993
Revision Date: September 5, 2007
2. COMPOSITION/INFORMATION ON INGREDIENTS
Ingredient Wt./Wt.% CAS# TLV PEL LD50 LC50
2-propanol 40 – 70 67-63-0 400 ppm 400 ppm 3.6 g/kg(oral/mouse Not available
2-propanone 10 – 30 67-64-1 750 ppm 750 ppm 6 g/kg (oral/rat) Not available
Isobutane (propellent –aerosol only)
30 75-28-5 Not available 1000 ppm Not available Not available
Talc 1 - 3 14807-96-6 Not available 2 mg/me Not available Not available

Cheers,

VRR

Vanessa R. Rhue
Assistant Collections Manager
Department of Vertebrate Paleontology

Natural History Museum of Los Angeles County
900 Exposition Blvd
Los Angeles, CA 90007
Tel. (213) 763-3248
Fax (213) 746-7431
www.nhm.org

On Wed, Aug 20, 2014 at 7:06 AM, Janet Waddington <janetw at rom.on.ca> wrote:

> Aplogies if this went out more than once.  My webmail can be quirky.
>
>
> I agree with Roger, ammonium chloride sublimation can enhance surface
> details.  It takes some practice and skill to get an even coating,
> especially with larger objects. (That is an excellent video by the way)
> One caution - this is a sublimate, not a powder.  In humid conditions the
> resultant very fine coating will quickly dissolve leaving a fine invisible
> film of nitric acid on the surface of the object, which could be
> problematic. On a humid day it sometimes doesn't even make it to the object
> in solid form.  Just because you can't see it does not mean it has
> "vanished into thin air". It can also end up in the air of your storage
> cabinet if it subsequently evaporates off the object.
>
> I would worry about not removing it especially if the object is sensitive
> to acid. If the object is not sensitive to water, it can simply be rinsed
> with a fine stream or quick dunk into water.  I have used EtOH on specimens
> that do not like getting wet (e.g. shales) but don't know how effective
> that really is.
> Also, be aware that the black coating cannot be completely removed.  It is
> used to give a uniform background colour so any colouring is not a
> distraction, and to give contrast to the white coating. But if you plan to
> use your object for display it might not be as pretty afterwards.
> That said, sublimation is still a superb tool for studying surface detail
> and has been used for decades in palaeontology.
>
>
> Janet Waddington
> Departmental Associate
> Department of Natural History - Palaeobiology
> Royal Ontario Museum
>
> >>> "Burkhalter, Roger J."  08/20/14 9:11 AM >>>
> I will echo what Christian has said and add that ammonium chloride coating
> is relatively easy and inexpensive. It also works on a variety of 3D
> objects where the surface morphology is in need of enhancement. We have
> coated not only invertebrate fossils, but vertebrate fossils (especially
> teeth), and neontological collections including egg shells, herpetology
> scales, fish scales, and, as mentioned, archaeological lithic artifacts. A
> short video that includes ammonium chloride coating may be seen here:
> http://www.youtube.com/watch?v=g-FiFtBQthY&list=UUtNiqiI7zdCFS8QGiiYYRfw.
>
> Regards,
> Roger
>
> Roger J. Burkhalter
> Collections Manager, Invertebrate Paleontology
> Sam Noble Oklahoma Museum of Natural History
> University of Oklahoma
> Norman
> www.snomnh.ou.edu
> http://commonfossilsofoklahoma.snomnh.ou.edu/
>
>
> From: nhcoll-l-bounces at mailman.yale.edu [mailto:
> nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Christian Baars
> Sent: Wednesday, August 20, 2014 3:21 AM
> To: 'nhcoll-l at mailman.yale.edu'
> Subject: Re: [Nhcoll-l] Dusting/powdering skeletal elements prior to
> photographing
>
> David,
>
> In palaeontology, invertebrate fossils are routinely dusted with ammonium
> chloride (NH4Cl) 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.
>
> 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.
>
> 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.
>
> Kind regards
> Christian
>
>
>
> Christian Baars
> Senior Preventive Conservator
> National Museum Cardiff
> Cathays Park
> Cardiff CF10 4NP
> 029 2057 3302
> christian.baars at museumwales.ac.uk
>
>
>
>
> From: nhcoll-l-bounces at mailman.yale.edu [mailto:
> nhcoll-l-bounces at mailman.yale.edu] On Behalf Of David Katz
> Sent: 19 August 2014 22:34
> To: nhcoll-l at mailman.yale.edu
> Subject: Re: [Nhcoll-l] Dusting/powdering skeletal elements prior to
> photographing
>
> Rachel,
>
> 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.
>
> 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.
>
> ... We'll see.
>
> On Tue, Aug 19, 2014 at 12:50 PM, David Katz > wrote:
> Hello,
>
> 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.
>
> 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?
>
> Thanks for you input.
>
> David
>
> --
> David Katz
> Doctoral Candidate
> Department of Anthropology--Evolutionary Wing
> University of California, Davis
> Young Hall 204
>
>
>
> --
> David Katz
> Doctoral Candidate
> Department of Anthropology--Evolutionary Wing
> University of California, Davis
> Young Hall 204
>
>
>
>
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