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

Wed Aug 20 14:45:52 EDT 2014

We are having drying tubes made by our chemistry department glass blower. I have not found a current source of Pyrex straight drying tubes so we have them made from quartz glass.

Roger

Sent from my Windows Phone
________________________________
From: Vanessa Rhue<mailto:vanessa.rhue at gmail.com>
Sent: ‎8/‎20/‎2014 11:32 AM
To: Janet Waddington<mailto:janetw at rom.on.ca>
Cc: nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu>; Burkhalter, Roger J.<mailto:rjb at ou.edu>
Subject: Re: [Nhcoll-l] Dusting/powdering skeletal elements prior to photographing

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<http://www.nhm.org/>

On Wed, Aug 20, 2014 at 7:06 AM, Janet Waddington <janetw at rom.on.ca<mailto: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://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> [mailto: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<mailto: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<mailto:christian.baars at museumwales.ac.uk>

From: nhcoll-l-bounces at mailman.yale.edu<mailto:nhcoll-l-bounces at mailman.yale.edu> [mailto: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<mailto: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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