Metal Detecting Q&A

[BAJR Host]

Many thanks steve. I can indeed confirm that you are a fully paid up member of the human race,

but seriously, I welcome you coming here prepared to answer questions. We all have preconceptions about each other.. from the
"but you rip it from the stratified soil - I am sure you could explain the topsoil and coil depths) to archaeologists just strip the topsoil with a JCB anyway... so why are so many worried about artefact recovery if they aren't going to look for them anyway...... et... ah good point!

I think the spirit of cooperation is what matters. and one the usual questions are dealt with we can move on to interesting ones.

is... I bet many archaeologists did not know about coil size ([:I] steady!!)and what that does. or how various metalic or even burnt stones can be 'tuned into'

anyway. welcome

Another day another WSI?

[Steve-B]

Hi David

Thanks for the welcome. (who said anything about being human, I'm a detectorist)

I really do look forward to answering all the usual questions as best I can and hopefully dispelling some of the misconceptions some may have as well as some of the concerns, some of the explainations may also sit uncomfortably with you archaeological sensibilities, but they will be honst answers all the same, for example, detectorists use a facility on their machines called discrimination,which basically allows us to reject small ferrous signals such as nails. From a detecting point of view, small ferrous targets such as these can mask other more intesting signals, they also tend to be irregular,
totally unrecognisable 'lumps' of rust and in some areas are so numerous that it would just be physically impossible to extract them all (although some do).

However from an archaeological point of view (and I am guessing here as I am not one), I imagine that a scatter of nails may be indicative of some kind of archaeology...

Being a bit of an adventurous guy, I also look forward to exploring new areas for discussion and ideas for cooperation.

Ok, to kick off I will give a brief overview on the subject of coils as David has mentioned them.

You can actually tell a lot about a detectorist from the size of his coil (steady, its not true what they say about detectorists with big coils having.....), by this I mean that all metal detector are retailed with the stock coil fitted, this is the coil that the manufacturer feels is best suited for general purpose use.

However, there are various sized after sales coils that have been developedfor some machines that have specific purposes, which for the sake of general discussion fall into two main uses.

1/ Smaller Coils:

Normally a smaller coil would be fitted for use on a site where there is either restricted acess for a larger coil, for example in a stubble field or where there is a high level of iron infestation.

Obviously the smaller size of the coil willenable the use to detect in between the rows of stubble far more easily than having to 'wade' through it with the larger coil, which can be extremely tiring.

In respect of iron infested sites, if you can for a moment imagine three mettallic targets roughly in a triangular setting, two of the targets are ferrous and one is for example a small copper alloy buckle. OK, now if I was to search over this with a large coil the two ferrous targets would mask the non ferrous buckle. However if I went over the same area with the smaller coil I would have the chance of finding the buckle amongst the iron.... simple?...well not really, I would experience a loss of depth capabilites and I would also have to serach at a much slower rate in these conditions... this is due to the recovery speed of the detector in hand (which varies from machine to machine.

The recovery rate is basicaly the time it takes for the detector to 'recover'from 'seeing'one target to the next, this is part of the reason why it pays to detect slowly when sraching in ferrous infected sites...you may well have rejected the ferrous, but the machine is still 'seeing' it and ;recovering'from it. ( I will cover the topic of discrimination later).

There are other uses for a smaller search coilsuch as in beach detecting, rock pools, amongst undergrowth etc.. but the above covers the general use.

2/ Larger Coils

Larger coils are normally fitted when the user has the need for more ground coverage and increased depth.

Ground coverage is fairly self explanatory, some of the fields we detect on these days are extremely large, and search time limited. Another application is for use when beach detecting, again, time is of the essence when detecting at low tide, so a larger coil will cover more ground faster.

OK depth, there are times when in the field when the stock coil does not give adequate depth capabilities (or it is imagined that it doesnt) in reality, this may be due to depth of top soil inland and depth of sand on the beach (this is a whole other subject as the depth of sand can vary from one tide to the next..sometimes dramatically).The user may be part of a group searching (under licence) for WWII aircraft, or (contraversial, I know) the user may be searching on pasture where the tagets may well have settled deeper.

A larger coil will therefore give extra ground coverage and some extra depth, bearing in mind that even the largest coil will only realistically increase depth by a percentage, it doent follow that if it twice the size it willgo twice as deep.

There are draw backs to using a larger coil, the first is that it will be unusable in areas of high ferrous content, or where a larger number of non ferrous targets present themselves. Secondly in some cases there may be a loss of sensitivity to some smaller targets.

There are a lot of urban myths surrounding the actual depth performance of metal detectors, many of them spread by detectorists who also exaggerate the sizes of other things... (fish for example)

Well there you are, coil sizes in a nutshell... I can see that this may suggest some questions to you, please feel to ask away...

[BAJR Host]

Unbelievable.... its 8 in the morning ... I have had only one cup of java... and I have learned something...

interesting stuff. and useful to archaeologists who want to ask for detecting survey, and therefore should be able to understand what they are asking for and the variations... top!

Another day another WSI?

[Silent Bob]

Hello Steve

I'm an archaeologist and am a firm believer in detecting on most sites I work on. If you sell detectors then how about some discounts (within reason) for archaeological contractors. Maybe Mr Host would consider setting up some kind of link with you such as the book selling section. Just a thought, besides the more units that buy and then actually try to continuously use a detector on a site (well, a productive one anyway) the better. I get bored of seeing them being used only once for about half an hour. Anyone who has done much detecting knows that it will many hours to find everything.

[Steve-B]

Hi Bob

Thanks for taking the time to reply.

It hadnt actually occured to em to try to ply my wares on here (must be slipping).

But, if Mr Host is agreeable then I am more than happy to offer a discount to you guys on the books etc.

I tend to present the detctors that I sell in a different way to other retailers.... normally you are offered the machine at the retail price together with a accessories (to a lesser or greater degree depending on price)... well I dont work this way, I start of with a heavily discounted machine only price (some manufacturers include one or more basics, some none).

I then advise the customer on essential accessories to purchase, (you would be surprised from the vast list of accessories just how few are actually essential) this way the set up is normally still way below retail.... to my mind the customer gets a great deal and I can sleep at night.... it works for me... well so far it has... if I am on the streets selling the Big Issue this time next year then I screwed up big time...

I am happy to discuss anyones needs and extra discounts for quantities etc and having worked on a couple of archaeological digs as a detectorist, I have a good idea of what is required...

Anyway.. a good idea, perhaps we could develop it further..

[Steve-B]

[u]A few basics</u>

Most modern metal detectors are what are known as Motion machines (some still work on the Non Motion technology) basically this refers to the fact that on Non Motion machines no movement of the search coil is require for elicit a response to a metallic target.

Conversely, some movement is required on a Motion detector for it to respond to a target.

The main differnce are that a Non Motion machine machine has to be tuned in and normally operates with a faint hum ( the Threshold Tone) in the back ground, they can tend to wander out of tune and have to periodically be retuned by means of a reset button.

Motion machines on the other hand are silent search (no tone until a target is located), they are automatic tuning and generally a little more usr friendly. The amount of movement required is minimal and is supplied by the normal sweep pattern.

It would be wrong to state that one system is better than the other they are just different.

Concentrating on Motion machines, the two main controls are the Sensitivity and Discrimination controls.

[u]Sensitivity</u>

Loosly speaking this is the machines depth control. There are some machines available where this is a fixed setting, however they can sometimes be rendered unusable.

The setting at which the sensitivity level can be set on any machine is in the main determined by then ground mineralisation conditions, namely the ferrous oxides in the ground. The lower the level of mineralisation, the higher the setting of sensitivity that can be used and the greater the depth capabilites to a degree.

The amount of mineralisation present in the ground can vary greatly and over very short distances, so if the detector suddenly becomes erratic, this may indicate an increase in mineralisation and the need to lower the sensitvity level.

There is another system present on the detector called ground balance that also deals with this effect, but I will cover that at a later date.

[u]Discrimination</u>

The discrimination circuitry allows the detector to recognise different metals, based mainly on their conductivity level (this is a simplification as there are also other factors).

The Discrimination control allows the user to reject certain targets. The noraml discrimination control will reject everything below the setting that the user has established. In the main, detectorists use this to eliminate only small ferrous targets..from the hobby perspective, everything else is potentially a 'good' target.

It would be impossible to eliminate larger ferous targets such as horse shoes oe spear heads for example as to do so would meant settng the level so high as to also elimnate other more desirable targets.

The second discrimination system is called Notch Discrimination. In this system the user is able to select a certain 'block' within the conductivity spectrum and still find all targets below this level and all targets above this level.

Mainly this system is used by beach detectorists to help eliminate pull tabs, however I am not a fan of this system as other targets will also be lost.

other types of discrimination can be found on some of the moreexpensive machines, where they have a learn accpet/reject edit system and certain types of finds can be presented to the machine which can then be programmed to respond to those targets or ignore them.

Discrimination and target information can be presented to the user either audially via the speaker or headphones and/or visually via and LCD meter.

I am not a great fan of using too much discrimination, notch or accpet/reject programmes.

However the sophisticated the technology may appear, it is however limited. By this I mean that modern metal detectors are normally very good at informing the user of the targets conductivity level, however, they cannot effectively differentiate between dissimilar targets exhibiting similar conductivity levels.

This is a basic explaination of these functions, please feel free to ask any further questions.

[sniper]

Cheers for all the info Steve, interesting reading. I generally have nothing against metal detectorists and have worked alongside them on a few sites, including one where a detectorist located and I dug 4 Roman coins from within a one metre square patch. However, I was speaking to a detectorist on a site a couple of weeks ago who said that he has detected objects and dug them to find he is also ending up with bone on his shovel, and while I was talking to him he got a phonecall from a detectorist friend who had dug for an object and ended up finding a burial. I am concerned that a lot of detectorists would not recognise when the bone is human and therefore when they have located (and potentially disturbed) a burial. What is your view on this and what would you suggest could be done to alleviate my concerns?

++ i spend my days rummaging around in dead people ++

[troll]

Greetings Steve-Many thanx, lots to digest so I will only ask one question that really does disturb me! Well, two actually
It`s only really been 14 years or so since it`s generally been accepted that, when and, if a hole needs to be dug in an area likely to impact upon archaeological deposits-an archaeologist should do it. Many detectorists have tried to tell me that they only scratch about in the top few inches-something I dispute in the strongest possible terms-how do we stop the destruction of context whilst detectorists go about their "hobby"? My second question relates to the disgusting trade in detected artefacts advertised in the back of so many detecting magazines(and on a certain website).If we are indeed making inroads into compromise between the pros and the antis-why is the metal detecting community not policing itself? Have many questions but, am old and knackered after slopping about in the mud...will come back another time.Many thanks for an interesting and informative thread.

[Steve-B]

Hi Guys

Thanks for the questions, I fully agree definately areas for concern..ok I will start with Snipers points.

Before I do, please remember that I am answering honestly from a detectorists perspective, my answers are in no way intended to offend.

Sniper, although your concerns are specific to the subject of human remians they do also crossover into the realm of Trolls concerns in repsect of just how deep should a detectorist dig.

I actually welcome questions such as these, especially in addressing Trolls closing remarks.. there are so very relevant.

There are no excuses that I would even want to think of that would explain why anyone should not have alarm bells ringing at the very sign of bone, whether they are capable of recognising human remains or not.

In my opinion it is the duty of any memember of the public, detectorist or not to act in a responsible manner, cease any and all activities and seek advice from the professionals.

There are still many areas of the hobby that cause concern not only to yourselves, but also amongst the detecting community.

The remedy for this is not especially complex and in my opinion should have been attended to long before now.

There are two hobby organisations, both of which in my opinion have been shamefully negligent in the areas of promoting 'responsible detecting' (not a popular expression in the hobby, but it is one we both understand). You only have to take a look at the website for each organisation and you will see there is very little or no in depth advice, no standards and the Code of Practice is pathetic to say the least.

Do not get me wrong here, I do not think that any amount of external pressure or 'advice' is going to remedy this problem, the cure can only come from within. If it doesnt, then I fear for the future of the hobby as I know it.

I have long been a critic of the main hobby organisation, the NCMD and quite vocally at times. Why?, well the NCMD is the one organisation that respresents the hobby at Governement level. I do not see how they can claim to do this, to negotiate on behalf of the hobby yet make no provision for the education of the people they represent, I find this wholey inconsistent with promoting good practice and thankfully I am not alone in thinking this.

The are talks taking place at the moment amomgst like minded detectorists on how best to address this problem. I do not think that they hobby needs yet another represntative body, but it does need a platform where a standard can be raised for others to aspire to.

This does actually lead on to the first of the concerns that Troll has expressed.

Detecting is not, has never been and never should be about disturbing the archaeological context, no arguements there from me.

As a dealer I am normally first point of contact with many coming into the hobby and as such I and the other dealers have a duty to promote best practice.

It really is a truism that 90% of all finds that are made while detecting are made in the first 4 to 6 inches... metal detecting is about the retrieval of non contextual finds in the disturbed top soil, it is not about excavation or disturbing the underlying archaeology and anyone that does has stepped over the line.

Despite manufacturers claims and the fishermans tales of "it was this deep" from detectorists it is true that some detectors in certain conditions are capable of detecting to a geater depth than the first 6 inches....

So how do we go about eliminating the possibility of the destruction of archaeological context?

Again, this can only be achieved by education and with the provision of information.

As I have said the first port of call is normally the dealer, which culminates with the customer taking delivery of a shiney new metal detector....

Bingo, this is the first opportunity to impart information.

To this end and with the blessing of PAS I have managed to persuede the larest UK importer and distributor of metal detectors to include a leaflet in with each and every machine that they distribute. Thy have also agreed to fund the costs of producing 5000 of these leaflets.

The leaflet is still be produced by myself and guy called Phil Dunning, another detectorist keen to promote good practice.

The opening message of the leaflet is:

"Now that you have purchased your new detector, please be aware of the responsibilites that go along with it"

It is not designed to pull any punches.

Another friend of mine has also mnanged to secure an agreement from one of the manufacturers, to include information on PAS with all the units they sell.

But this alone is not enough, as I have said it is the duty of the hobby and its organisations to promote good practice and provide comprehensive information on issues such those raised above.

I hope this reassures you in some way that there those within the hobby seeking to address these issues, early days with a lot of graft ahead of us.

The second subject you have raised is in respect of the selling of artefacts.

OK, this is not quite the simple topic as the question would indicate,as in my opinion it brings into question the whole subject of private collections and the right of the individual to not only own but to trade the artefacts that they have in their keeping. (it is also worth mentioning here that it is not just individuals that have been known to sell artefacts, but museums as well).

I know that the answers that follow are not going to be popular, but they are honest ones and it is only by my answering you in this way that you will be able to gain an understanding of this topic from a detectorists point of view and allow for a starting point to further discuss these issues, offering a political answer at this stage would not do any of us credit.

First of all where do you draw the line on private ownership of anything and everything?.. do you extend this to inlclude, antiques, stamps, fly fishing hooks. what about the house you live in and all your possesions?

Or do you just limit this to artefacts, because that is where your archaeological interest lies? Apologies if this sound flippant, but it is a valid consideration.

I personally do not have any moral problems with responsible private collecting, to me this is the key to diversity, flexibility and exchange of thought and ideas.

Responsible private collecting - to me this means that all artefacts within a private collection have been properly recorded and are cared for and stored in an approved manner.

I do not agree with the selling of unrecorded finds or items that potentially fall into the realm of the treasure act. However if I had a particular area of interest within a collection I would not be against making a purchase that would help compliment that collection and hopefully help build a better understanding of that particular area.

Also if I had a find that I felt would help compliment the collection of another, be it an individual or a museum I would not be adverse to selling an item to them. Having said that in some cases I have been known to give freely an item that was of interest to another to me personally, the hobby is not about making money.

When I make a find, I can honestly say that the monetary value of that item has never been foremost in my mind, quite oppsite in fact. To me the inherent value of an artefact is in the information that it can provide us. The most important consideration we have at present is to ensure that all detectorists become recording detectorists.

Troll, please try to remember that there a great many areas for improvement within the hobby... trying to solve them all with one blow from a sledge hammer will not have the desired effect, quite the opposite.

However, working together to encourage good practice one step at a time will lead to far more solid and longer lasting relationship. At the end of the day it is familiarity that will breed acceptance of new ideas and better practice.

It is rather late, but I do hope that I done fair justice to your questions (please forgive any typos)

[mercenary]

It is very reassuring that there are MD's out there like Steve. It confirms that our hosts tireless efforts at co-operation between MD's and archs are not misplaced.

I agree that the hobby must change from within, but in the same way that archaeological contractors rarely improve voluntarily how will irresponsible MD's change without some punitive measures?

I don't know what these should be, but change to the antiquities market would seem to be a good start.