Wednesday, 28 October 2015

Artefact Hunting, the "Lesser of Two Evils"? More on "Fragmentation".

John Hooker, the antiquarian fellow who runs a blog called "Past Times and Present Tensions" is determined to show that artefact hunting, ripping archaeological finds willy-nilly out of a site, is some kind of a "lesser evil". The greater evil is farmers. Farmers farm their land and collectables (their collectables on their land) get damaged.  I queried ('Hypocrisy and twisted Argument in UK metal detecting' 22 October 2015) the "evidence" he had presented to support his thesis that artefact hunting is always a form of "rescue" (a common leitmotif these days). Now, he's decided to come back to the subject: "it has come to my attention that some have misinterpreted the information to the point that one person even imagined that all damage was done in ancient times". It's "come to his attention" because he's been reading my blog, but cannot be bothered to actually discuss it here. Off he goes instead on on another of his pathetic tangents ('Dean Crawford — Living among the Dobunni: more on fragmentation' ) Tuesday, 27 October 2015
This blog post is an image-rich display of the damage done by modern agriculture and is a necessary addendum to the post Fragmentation [...]these are impromptu and/or "kitchen-table experiments" and not "hard-science" laboratory experiments. [then a chip-on-shoulder jab at archaeology and its place in the humanities] Let us call them "an aid to common sense".
The problem here is that it is not clear who is writing what . Mr Hooker says that "Dean [...] has sent me a wealth of material for this series. As editor, I have to sort all of this into various themes and then decide where each should best fit within the sequence". So it is unclear who is responsible here for what, and what modifications have been made to the original material in "editing". Why Dean Crawford cannot just write his own stuff and needs Mr Hooker's help is a conundrum (I'll come back to the significance of that for the 'Hooker paradigm on artefact collecting' in a later post, probably next week). Anyhow here's what Hooker has made of it all. He has six "common sense proofs". I think it can be shown that the majority do not in face bear out the correctness of the metal detectorists' argument. This is not my "imagination" (as Hooker phrases it), it is cold hard logic:

1) Hooker says that "it is magical (sic) thinking to suppose that a field can be ploughed over several seasons without fragmenting metal objects highly crystalized after more than a thousand years in the ground". Well it is not, because as an archaeologist one can meet metal objects in the ploughsoil - in fields that have been ploughed for hundreds of years in a row - which are not overly fragmented. The majority of archaeological and historical metalwork is not freshly fragmented. This is after all (and as I point out time and time again to have it ignored by the hoik-it-out-crowd) what we see on eBay and the PAS database (and the pirate UKDFD frequented by the likes of Mr Crawford). I pointed out earlier that at the Water Newton Rally where this was claimed, publication online of the photos of all the objects recovered showed the converse, very few of them exhibited signs of fresh damage.
Of course buried metal objects do not crystallise (or even "recrystallise'). That's why we can take them, saw them up and do metallographic sections of them. Stuff and nonsense from Mr Hooker.

Nobody is saying that metal objects are not damaged by the plough, what is being said is that artefact hunters and their supporters overemphasise the scale of this effect, pulling out some showy examples (see below) and suggesting they are in some way typical - when they must know that they are not. In my last post I challenged Mr Crawford to show the entire assemblage from the site from which he selected a handful of cruddy bits which he not only says are plough damaged but show the "typical plough damage" seen on his sites. He of course has not yet done so, just produced there other selected cases. Let me guess that the reason he has not done what I asked is because it proves I am right. My common sense tells me that selecting the evidence to suit the thesis you want to prove is not a "kitchen sink experiment", it is quite simply deceitful.

2) John Hooker says: "when I was a child, I frequently saw Roman coins with active (modern) corrosion lying on the surface of ploughed fields. I never collected any of these as most of them consisted, virtually, only of corrosion products". I really do not say how Mr Hooker thinks he can differentiate "Roman" corrosion on a Roman coin from "eighth century corrosion", "fourteenth century corrosion" and "modern corrosion". And when the self-declared polymath was still a child too! Maybe he'd like to give us a rundown how one can do this. How did the child-genius Hooker know that these coins were not ploughed out of an underlying deposit already in that condition?

Interpreting a context in archaeology is a matter of taphonomy. I think both Mr Crawford and Mr Hooker are guilty here of assuming that any changes they can see took place only where they saw them, in the ploughsoil. I think making that assumption is cardboard cut-out thinking.

3) Serendipity: "Dean noticed that a farmer had spilled some of his fertilizer in the farmyard and he gathered some of it to perform the experiment pictured above. It represents the effect of fertilizer in the field over a longer period of time but of course does not include the impact or pressure damage done by farm machinery". The results are pretty. I am sure they'll not mind me publicising their "results" by reproducing the photo. Look at this:

Photo copyright Dean Crawford (reproduced after Hooker)
A "kitchen sink experiment" indeed.  Three weeks it says, that's about it for description of experimental method. We have in the bottom left some British pre-decimal coins which look as if they came from the soil, all greeny they are. Above them we have them half buried in soil on the ground surface, with some identified white granules scattered over them. The soil look pretty dry, we have no data on soil humidity, pH or what that fertiliser is. Over on the right we see the same coins covered in powdery blue green efflorescence. This, we are told is after "three weeks". I suppose we are expected to think, "ah well, if that's what happens to artefacts after three weeks in the fertiliser, then perhaps hoiking them all out onto EBay makes sense".

I really do not understand what this is "proving"  - we all know that you can make copper alloys go interesting colours by putting stuff on them, that's how you get chemical patinas on sculptures and fakes.  No news there. What we need to know (and are not told) is what soil processes are being duplicated here. Nobody would apply fertiliser to anything at the density Mr Crawford has used to force this colourful corrosion. They'd end up criminally polluting the groundwater for a start.

I really do not see how one gets from what we see of the coins in the field to the patterns of corrosion in the final shot. One of the coins has six granules one one edge, but all four coins are shown as evenly covered in corrosion. What does the underside of those coins look like? Can we have the precise experimental methodology please, was the fertiliser reapplied after rain, how did the moisture of the soil change after the in situ photo was taken?

Certainly something has happened to these coins, copper ions have migrated out of the original corrosion layers or the metal to produce those colourful salts, but in what quantities? What is the reaction here? What are those salts? More to the point, just how much is the coin (the collectable) damaged under this powdery efflorescence? If you look, the original green 'patina' (from before the experiment) shows through in places, in other words, it and any underlying cuprite (oxide) layer are not damaged, there is just a localised bloom outside it. On the right of the picture however one can see green powder on Mr Crawford's hands, this bloom is incoherent. I get the feeling that most of it would brush off pretty easily leaving the coin perfectly intact and legible below.

But, in their desperate attempt to use artificially-coloured coins to prove a point, both Mr Hooker and Mr Crawford miss the most obvious fact about the point at which their experiment started. The coins in Mr Crawford's hand before the experiment are green. They have a smooth (and apparently stable)  patina, just like the thousands of pre-decimal coins shown day after day, week after week, month after month in look-what-I-found today postings on detecting forums, websites and You Tube videos. Exactly the same. And almost all of them come from ploughed fields, most of them have been lying constantly in the sort of fertiliser solutions which Messers Crawford and Hooker claim are so damaging and... they are not damaged in the way that Mr Crawford's "experiemnt" says they should be.

I said it in the last post, but will say it again, the archaeological value of the four coins in Mr Crawford's hand after enforced copper salt growth is not in any way diminished by them changing colour. It is their value as  collectable which Crawford and Hooker are concerned about.

4) More serendipity, Mr Crawford found two bits of a broken gold coin which joined:
Dean found these two fragments of a gold noble three years apart and over thirty yards from each other in a ploughed field. The increase in deterioration can be clearly seen. The wear on such high carat gold is not due to the loss of material but due to the redistribution of gold molecules over the surface. If you think of spreading butter on bread you can get an idea of how this works. Soil particles "hammer" the gold. The fragmentation was caused by farming machinery.
Again, the assumption is being made that because they were found in ploughsoil, the only mechanism by which they could have been affected "must" have been there.. I am going to republish the photo from Hooker's blog with one modification. I show where there are clear traces this coin was deliberately cut and snapped.
Photo Copyright Dean Crawford, reproduced
after Hooker
with modifications by the author
The fragmentation was caused, as is shown by a clear burr and cut mark, by human hand, before it got into the ground even, let alone the ploughsoil. The fantasy about soil particles hurtling dynamically towards the gold like a sandblaster or micrometeorites in space is just that, nonsensical fantasy of an antiquarian. If you look at the way the larger fragment undulates, it has been folded and then straightened after it was cut. The relief is flattened because, most likely, it has been hit with a hammer. This is not fantasy plough damage, it is damage caused when somebody treated a gold coin as bullion. I think the reason how when and why that happened is an archaeological problem. But it certainly has nothing to do with plough damage, and certainly nothing to do with policies on artefact hunting.

The Crawford/Hooker Dynamic Particle Ablation theory ("think of spreading butter") seems not to be mentioned in anything I have read on the Staffordshire Hoard (some of which was excavated from active ploughsoil levels, and the pure gold thin cell walls are very fragile), neither does it seem to be much evidenced by other gold finds made by Mr Crawford (here for example). There is not a single mention of it anywhere in any Treasure report of the PAS I have read (and I've read a few). I think we can conclude that this, like much else collectors say,  is a figment of an antiquarian fellow's imagination and the self-serving inventions of a detectorist who fantasises about himself "living among" a long-vanished social group. 

5) Hooker then shows pictures of "two more Dobunni coins, but the fresh fragments all found within ten to fifteen yards of each other, a few inches deep on ploughed land." (Leaving aside the wquestion of whether the depicted fragments really are of the same coins), as I wrote, nobody is denying that tractors (but also hand-hoeing) damage finds. The truth is though that there are far more complete and undamaged Dobunni coins in databases and collections all over the world than there are ones so spectacularly damaged as the two Mr Crawford pulls out for his bragging and our delectation. So if 1% or even 2% et damaged like this but 98% do not, is there any reason to change our minds about artefact hunting? (answer; NO).

6) It goes on... and on: "Anglo-Saxon Great Square-Headed brooch fragments, all found over a thirty square yard area. Ninety percent of the brooch recovered, reconstructed and recorded". No, it has not been properly recorded There is only a record in the private pirate UKDFD "Findspot: Near Worcester Recorded elsewhere: No " but it also says "Associated finds consisting of 7th century strap-end and silver penny of Coenwulf - UKDFD 701" now that in turn says "Findspot Near Evesham Recorded elsewhere: No". So two associated finds recorded as "near" two places 32km apart and neither of them properly reported with the PAS. Scandalous.

This brooch is fragmented in a way which suggests it was lying flat and was squashed by a heavy weight - like a tractor or earthmoving machine driving over it. That is suggested by the crushing of the edges of the break through the headplate. It is still recognizable as a GSHB, it is perfectly possible to fit it in Hines' type series of the class, you can measure it, study the technology of its production and decoration, in short, as an object, it is every bit as valid a piece of archaeological information in its present condition as it was when whole. Its value on the commercial market may be reduced by it being broken and needing gap-filling, and that seems to be what Mr Crawford and Mr Hooker are interested in, and thinks everybody else should be. To the extent that they present pars pro toto selections as "evidence' and make a number of wild assumptions which do not stand up to scrutiny. What we know nothing about is the context of deposition of this loose object, or the context of discovery. Was it recovered from a pipeline wayleave for example? The "record" does not say.

Mr Crawford, please show the whole assemblage from the site from which you selected your handful.What are you hiding?

[A while ago after reading about Mr Crawford's coin-colouring "experiment", I put my hand in my pocket and pulled out a whole lot of copper alloy loose change which contained some pretty cruddy pieces, but also obviously I'd recently been to a shop which had just opened a bag of freshly minted coins. This gave me an idea, half an hour later I was in a local coin shop and bought a couple of dugup Russian kopieki. Tomorrow I am going to try and duplicate Mr Crawford's kitchen sink experiment with the fertiliser: watch this space for the Warsaw Chamber of Numismodeath].

FOOTNOTE 29th October 2015
This post dealing with metal-detecting-misdirection and misinformation is already too long. Mr Hooker imagines he answers one (just one) of my criticisms. He's referring to one sentence in my point 1 about  "metal objects highly crystalized after more than a thousand years in the ground" and I refer him to metallography of ancient objects which indicates that his statement about metal objects crystallising in the soil is an over-generalisation. The reason why metallurgical sections of metal objects is used to determine manufacturing technique is precisely because the metal core of most objects retain more or less unaltered the structure imposed at the time they were made and used. The antiquarian fellow hasapparently not heard of such a thing and writes how a coinshop owner just down the road from him has:
an ancient Greek silver coin which had been broken by someone who had dropped it on a hard floor exposing its crystalline interior. You cannot, of course see such a thing by sawing a coin in half as the surfaces exposed are new and appear quite smooth.
[note the appeal to 'special antiquarian knowledge'] Well, that will be news to anyone who (like the author of this blog) has ever done any of it and polished, etched and examined such a section. There is for example an online book (we know how collectors like Mr Hooker like their books online) by David Scott 1991 'Metallography and Microstructure of Ancient and Historical Metals' with enough pretty pictures to make the point. There are others. Mr Hooker needs to do some reading ... (he might like to start on page 21 of this book for the specific case I suspect has led him to his mistaken over-generalisation. There is other stuff for him to find online about the 'age embrittlement' of silver through discontinuous precipitation of a phase of an alloy and/or differential corrosion from a materials-science/conservation point of view, some of it going back in its printed [paper] form to the 1950s)

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