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Archive November 2011

Victoria Park Tunnel Pistol found Not Guilty Brigid Gallagher Nov 17

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Earlier this year I wrote ‘Criminal minds brings archaeology into mainstream news’ as I was amused by the insight into mainstream media mentality.  The possibility of an unsolved ‘ancient’ murder catapulted the archaeology being conducted as part of the Victoria Park Tunnel development into the NZ Herald, rather than the story of Auckland’s early occupants being the driving force.

The double triggered pistol found in the bottom of a well, with the appearance of 1 trigger depressed, made national news.  This single piece of evidence was enough to turn the tide of media interest in archaeology; with the news reporters imagination being ignited by the prospect of an unsolved crime….and perhaps, danger!

In the NZ Herald it was stated by one of the archaeologists involved, Dr Sarah Phear, that the pistol had been sent to a conservator for treatment.

Well the pistol found its way to my work space at Mishmish Productions for conservation and analysis.  In doing that my brief was to:

  • reveal the original object,
  • type, date and provenance the pistol,
  • stabilise the pistol

My secondary aim was to establish whether there was any possibility that this pistol could have been discharged immediately prior to disposal in the well…and therefore support the idea that this was a murder weapon. 

Like any good archaeological or Police investigation, focussed questions and strategies are key to good results.  Why conduct analysis without genuine questions or purpose?

This weekend, the Victoria Park Tunnel in Auckland opened its doors and it seems pertinent to share the sciences that have been used to investigate and understand the pistol better….and what methods were used to show that it would NOT have been used in criminal activity, in fact any firing activity, just before it was dumped in the well.

 drawings details and xrays copy

 

 

 

 

 

 

 

Above: The Original Pistol

 

Evidence 1:

The Burial Environment and Soil Science

The pistol was found in the base of a well in clay, with the handle missing.  The clay surrounding the pistol was fairly anaerobic (had minimal oxygen content) and because of this the preservation of the pistol was relatively good.  There were hard concretions on the surface of the pistol suggesting there was some water percolation through the burial environment.  Movement of the pistol itself once within the well is likely to have been minimal.

Understanding the burial environment and the surrounding soil meant that prior to any analysis or treatment there was a good chance that the original surface, form and any makers marks would be preserved beneath the metal masking corrosion.

Because of the preservation capabilities of the anaerobic clay, and the good preservation of the pistol, it is highly likely that if the missing elements of the pistol such as the handle and hammers were attached to the pistol at the time of disposal, they would also have been found close by, if not in the original positions.

Understanding the nature of buried soils and how they affect different materials found in archaeology meant that reconstruction of the ‘ last hours of the pistol’ were possible, once it was disposed of in the well

The conclusion is that the pistol was discarded after the handle and hammers were removed from it, and therefore not a ‘murder’ weapon.

This is supported by…

Evidence 2:

Corrosion Science

The nature of iron corrosion results in a layering effect, both over and under the original surface of an object, in this case a pistol.  As corrosion progresses, the iron metal attempts to convert to its most stable form, magnetite, the product most stable and akin to the rock from which the iron was originally extracted.

The rate of corrosion is accelerated by the environment and use of the artefacts.  In this case corrosion was consistent across the pistol, suggesting all metal currently exposed was also exposed to the burial clay at the same time at the time of burial.  The corrosion response or appearance is likely to have been different on the areas originally hidden by the handle, if the handle had still been attached at the time of the discard.

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Above: Xray from the top of the pistol showing metal corrosion and loss

Any differences in corrosion seen on the surface were related to the techniques used to finish the metal during pistol production.

In areas where corrosion forms in the presence of moisture and oxygen, such as in the internal mechanisms of a pistol that could not be completely encased in the burial clay, voluminous corrosion masses occur, full of holes with low density.  It looks like a hard skeletal like kitchen sponge.  This happened in the void areas around the triggers.  Hence the appearance of one depressed trigger…and hence the CSI verdict.  Murder….

The conclusion is that the pistol was discarded after the handle and hammers were removed from it, and the triggers were corroded into the one trigger depressed position by chance, and therefore not a ‘murder’ weapon.

This is supported by…

Evidence 3:

X-ray Analysis

X-radiography, like in the x-ray of bone, penetrates metal differently depending on its composition, condition and technology or form.  X-ray was used to show how and where the pistol was used, if there are any breaks or areas of fragility in it, if there was any decoration on it and its technology that could not be seen from the exterior and due to masking corrosion.

The x-ray results showed the pistol had been fired and there was loss to the open barrel ends, making them vulnerable during any conservation treatment or rough handling.  There were other areas of loss particularly along the barrel, probably related to increased corrosion due to the way the pistol sat in the well. There was no evidence that the pistol was a sawn off variety, this was the original length.

X-ray also showed technological features such as; the barrels were of the turn off type, developed to make the pistol easier to clean and was the point the ammunition was loaded into the pistol.  The screw threads could be seen, and the nest on to which the musket ball would have sat.  The percussion nipples were visible with the channel into which the powder would be packed prior to firing.  This was an early precursor to the breech loaded firearm.

 

No decoration or markings were visible, but this may be due to human error in the setting of the x-ray parameters.  Different exposure strength and time reveal different features and information. The machines in the facility I use in Tauranga were showing BIG alarm bells as the parameters I set were not safe for human use (that is, not safe for a person having an xray, but ok for us in an appropriate safe area).

 drawings details and xrays copy1-6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Left: Technology revealed by x-ray

 

The conclusion was that this was likely to be a mid 19th century personal defensive firearm, and had not been tampered with prior to discard in the well, ie was not a sawn off shot gun!

This was supported by…

Evidence 4:

Conservation Stabilisation and Treatment

Desalination of the metal occurred over a 3 month period in an alkaline solution, to both aid the removal of salts and chloride irons, but also to loosen the hard concretions on the surface, masking the surface of the pistol.

Following this treatment, and original surface was accessible by mechanical cleaning, and the true and original form of the pistol could begin to be revealed.  The original surface was identifiable, different metals and metal treatments were seen (the barrels are steel Damascus barrels and probably were treated to ‘bluing’ during its life time, the original surface of the box lock had a mottled appearance, suggesting it to had a decorative and aesthetic quality to it…ie it was cared for.

Beneath the corrosion on the side of the box lock the original proof mark stamps were revealed, in pristine condition, as though they had been stamped yesterday.  They proved the pistol had been produced in Belgium (Liege).  The markings narrowed the date range of the pistols production down to 1853 to 1877, at a time with these pocket pistols were immensely popular across Europe and being exported by the Liege to the UK and USA and out to the colonies.

 

The conclusion is that this is a mid 19th century pocket (or muff for ladies) pistol which originated in Belgium and found its way to Auckland, New Zealand.

drawings details and xrays copy

 

 

 

 

 

 

 

 

 

 

 

 

The Conclusion

So here you have it…some of the techniques used in the forensic analysis of an archaeological object.

Without a shadow of a doubt, the verdict is…

  1. It is a box lock, breech loaded, turn off barrel pistol example
  2. It is a personal defensive weapon, called a pocket, trouser or muff pistol, used by both men, women and Police
  3. It came from Belgium in the mid 1800’s
  4. It was fitted with Damascus steel barrels (origin unknown)
  5. It was cared for, for at least part of its life
  6. Its last port of call was Auckland, New Zealand
  7. It was stripped of its handle, hammers and springs prior to discard in a well in St Marys Bay

And…

It was not a murder weapon.

However….this is a fantastic example of a nice archaeological artefact, that was given the opportunity to have much more of its story told than most historical artefacts get given, and contained within it was more than anyone realised (Thanks Clough and Associates and the imagination of the media)….with the help of a range of scientific techniques and skills.  And I am sure there is a lot more information still contained within its silent shell!

Note: The conservation of archaeological and other cultural materials should be conducted by a trained professional.  Ethics, guidelines and best practise are intrinsic to good advice, treatment and method.  For recognised professionals in this field please refer to the New Zealand Conservators of Cultural Materials website and database.  For those who do not see my name…I am a member, I have just not got about to filling out the form!!

The Self Preservation of Grass Brigid Gallagher Nov 04

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The sun is hot outside, the cicadas are buzzing, the next door neighbour is mowing their lawn, the beginning of summer is here….

             You step outside your house into the noise and heat of the day, and….

Mmmm…. that lovely smell of newly cut grass.

Its fresh, green and very inviting.

But the same cannot be said for the small, generally unseen members of our gardens. While we might love the smell of fresh cut grass;  insects and other ground bugs don’t have the same reaction. 

This week Gerald Smith, Associate Professor at Victoria Universities Chemistry Department and Heritage Materials Science programme presented a paper to members of the New Zealand Conservators of Cultural Materials conference at the Carter Observatory in Wellington.

Smith and a team of chemists and heritage professionals, including weaving and fibre expert Rangi Te Kanawa, have been looking at the effect of acetic acid on Maori textile fibre. Known as the vinegar effect, they have been testing the production of acetic acid during the degradation of fibres used by Maori, namely Phormium tenax (harakeke or New Zealand flax).

The physical effects of degradation of these fibres include colour change, embrittlement and in extreme cases, loss.

But they have found through accelerated aging tests that not only is acetic acid produced but also furfural (an aromatic aldehyde derived from a variety of agricultural byproducts) and Coumarin (a fragrant chemical compound in the benzopyrone class). 

Coumarin is what we smell and enjoy when we take a deep breath taking in the aroma of freshly cut grass (it is also commonly added to pipe tobacco and some alcoholic drinks to lure us into partaking)

Coumarin is also what insects smell and then run for cover (I am not sure if that should be taken literally!).

Coumarin is volatile, plus a natural anti fungal and pesticide.  Bugs are repelled by it…but what appealed to me in Smiths presentation… was how in the production of these anti-bug properties, grass is giving itself a chance to heal without the being compromised to the chomping jaws of our garden dwellers.  It is an act of self preservation and…natural conservation.

But what about historic and prehistoric Maori fibre textiles…

Like acetic acid, coumarin is photosensitive (essentially this makes colours fade) and its evolution of hydrogen peroxide also causes more damage (just think of your friends bleached hair and how dry and brittle it gets with repeated application!) to these beautiful examples of Maori taonga (treasures).

Limiting the presence of such chemicals as acetic acid and coumarin can help to preserve beautiful fibre textiles such as kete, cloaks and the like, in private and public collections.

So what to do…even if you cannot smell vinegar or freshly mown grass next time you open a draw with some beloved fibre textiles, in a museum or in your own home…Smith says

…lower the moisture in the air and the temperature if you can, but most of all, get the air moving and flush away those chemicals! 

And next time you walk over that freshly mown grass, take a moment to stop and think.  You are witnessing a wonderful moment in the regeneration of our natural environment.  Grass sending out its signal that it needs time to heal.  And I reckon that is very cool!

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