Pull Tabs...

I thought this was interesting about the history of pull tabs...... thou simple it does give you some idea as to dating a hunting area.

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Very interesting, thanks for sharing.

I been collecting Beer cans off and on since it was hot in the 70s. It helps as makes You know age of certain tabs
when found to help date a park.

Remember certain areas have specific tabs and getting to know your area is a plus..many areas differ so not playing on a level field when reading posts from fellas from different States.

Areas can very.... even moved dirt. Another thing.... these tabs may very as to their target ID.

Here is some interesting reading.

[sha.org]

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Back in '04, I penned a 3.400 word paper about 'The Anatomy of Pull Tabs' for the UK magazine, "Treasure Hunting"

Des D Wrote:
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> [i.postimg.cc]
>
> Back in '04, I penned a 3.400 word paper about 'Th
> e Anatomy of Pull Tabs' for the UK magazine, "Trea
> sure Hunting"

Did it go like this.... I hate them, ugh. = 3.4 words

Ozzie,

It was more like 4,200 words...I just re-visited the article and am reproducing most of it below (3,700 words). (I have omitted some paragraphs relating to people collecting both beer cans and tabs and charities collecting both as a form of revenue for them)

Bear in mind the article is 'Minelab centric', because I was working with them when I wrote it. The 'Explorer' had morphed into the 'Explorer ll' and at the time of writing was one of the most popular detectors models in the hobby.

Des D

The Anatomy of a Pull Tab
by Desi Dunne


Imagine you are carefully searching a new and productive site. Some finds have been made and every sweep of the search coil gives you that tingling at the back of the neck feeling as you anticipate the sheer excitement when sound bursts through your headphones, very alarming as you are listening so carefully. Yes, there it is again, a good signal – switch to pinpoint – bend to dig - carefully now so you won’t scratch your prize – yes – there it is – a glint of metal – more soil removed – “Oh no, it’s a pull tab, how did that end up here?”
So it continues – the ever-present drama of the dreaded pull-tab, common to searchers everywhere.
So what is it about this particular metal piece of which millions have been discarded into the soils of our fields and sands of our beaches that drives us mad? Just what are they and how come so many are found? Why are they such a nuisance to detector users? What can be done to avoid them?

History of Pull Tabs

To examine the history of the pull-tab one really has to refer back to the origins of the tin can in 1795 when Napoleon offered a 12,000 Franc prize to anyone who could come up with a way of preserving food for his marching armies. Nicholas Appert, a French confectioner won the prize by preserving food by sterilisation. However, it wasn’t until 1810, that an Englishman, Peter Durand received a patent for a tin-plated iron can as a food container. Craftsmen of the day were only able to produce 60 cans a day. Whereas modern beverage can makers are producing over one million a day. This is a daunting thought for us detector users all across the world.

From such humble beginnings the can evolved in stages through many inventions and re-inventions and in 1922 the American’s perfected “crimping” lids onto cans, which resulted in faster manufacturing speeds. During the next forty years many can types were invented and improved upon. Then, in 1963, Mr. Ernie Fraze, an American from Dayton Ohio, working with the Alcoa Group invented the “easy-open end”, what we know today as, “the removable ring pull”. This development had a dramatic positive effect on the sale of carbonated beverages because it made it so easy for the consumer to open the can. Prior to this the can was pierced using a triangular steel opener to put two holes at opposite sides in one end.
Finally, in 1989 the “stay-on the can” type pull-tab was introduced. In 1995 coloured tabs were introduced for marketing promotions.

Physical properties of pull tabs

Q. “What exactly is a pull tab?”
A. A pull-tab is a formed piece (or pieces) of aluminium.

Q. “What is aluminium?”
A. Aluminium is a very light metal with a specific weight about a third of that of steel. Physically, chemically and mechanically aluminium is a metal like steel, brass, copper, zinc, lead or titanium. The main properties, which make aluminium a valuable material are; its lightweight strength, recycle value, corrosion resistance, durability, formability and conductivity. In relation to its weight it is almost twice as good a conductor as copper.
A square metal pull-tab measures 24 X 15mm – the old ‘ beaver tail ‘ round tab measures 48 X 23 mm. A typical coin measures around 24 mm.



What is Discrimination and Pull Tab Discrimination

Most metals have a measurable conductivity – a Phase Response. This is the ability of a particular piece of metal to generate an “eddy current”. This eddy current is induced in the target by the electro-magnetic field from the transmit winding of the coil and when interrupted (by a target) the balance of the transmit and receiver magnetic fields are upset – resulting in a signal. On metal detectors, which have a rotary discrimination control knob with a range of say 0 – 10, at different numeric settings, various metallic targets will “drop-off”, and no longer produce a signal when passed across a search coil. A pull-tab, just removed from a beverage can and discarded on the ground, will respond at a high conductive level if a metal detector’s search coil is passed over the tab. It usually remains in this very conductive state for many years. Unfortunately, that is the problem – they are very reactive to metal detectors. The signals received back from pull-tabs can often mimic some of the same signal characteristics of gold rings of different carat content. Sure, we can “lose” the tabs if we so desire and not dig them at all but this would be at a high level of pre-determined discrimination set in by the detector operator, which is called Pull-Tab Discrimination level. On many metal detectors this point would be reached at a discrimination level of about 7. This still allows us to go through other additional discrimination points. However, metals usually detected at settings above 7 would be nearly always highly conductive copper and silver coins and other large objects. Few rings would be found at all unless they were, for example a typical College or High-School ring, which tend to be very large and still a good target to most metal detectors. Anything with a conductive value the same as and lower than that of a pull-tab would not be found at all. The list of items that could then be missed includes, many gold rings, as lots of rings are low-carat, and tiny low-conductive coins of either gold or low grade silver. Clearly this is not the way to go. So what are the solutions? How can we go about the hobby of metal detecting and increase the odds in our favour by finding the rings and small coins and not recover so many pull-tabs?

Notch Systems

“What exactly is meant by a notch system?” Here is an explanation, which I usually give.
Notch is a small window of conductivity and can be used to either accept or reject a set point of discrimination level. Imagine you are sitting in your conservatory at home looking out a large window. At the top of the large window there is a smaller window, which, can be opened for fresh air so you won’t have to open the larger window as by doing so might result in a huge draught blowing in and chilling everyone inside.

This is precisely what Notch is – it is a tiny secondary area or window of rejection or acceptance relating to a level, or levels of conductivity, and when utilised allows you to open the larger window of your primary
discrimination but set to a very low level. So you can have your Notch set to discriminate out just one high conductive item, usually a pull-tab, and your regular Discrimination set to discriminate out low conductive items such as small rusty iron pieces and low-grade foil pieces. Even here, it is critical because some small gold rings and thin silver coins can also mimic the characteristics of foil. So it is essential to keep your primary discrimination level as low as you can get away with and not dig too much foil but still find the coins and rings while ignoring commonly found pull-tabs.

Take a look at the pull-tabs shown in Fig’s 1 - 4 and what instantly becomes evident is the huge variety of pull-tabs which either were or still in use.
In Fig.1 if you look carefully you will see that there are some differences between them. They will also “look different” to your metal detector. On the top row the apertures on all the tabs are different. Second row have their metal connecting pieces still attached. The first one on the third row is completely different to all the others. In the last row you can see a broken tab and a folded tab. All of these pull-tab types can produce different ‘eddy current flows’ on your metal detector. Eddy currents will flow around the outside of the tab, another will flow around the holes in the tab and if a small flange is still attached, so too another current can be created by this. So a single tab can create many eddy currents. So you can now appreciate that if you discriminate out one sort you may still find another. So what to do?

One possible solution can be seen in Fig.5. You will see seven colored pull-tabs of which three are identical – these are on the top row, second one in and first and second in the second row down. If you find yourself in the situation of constantly unearthing the same pull-tab type but not many other different types you could then initiate your Notch Reject control. You could set your detector to reject only one type of pull-tab: the one you are finding most of. The Minelab Sovereign Elite is perfect for this demonstration. To see how this will look after it has been done on the Minelab Sovereign Elite, please look at Fig.6. Now, I will explain how and why it is done.

If you are a summer beach hunter you are probably plagued by pull-tabs and foil. Here again, foil comes in all shapes and sizes and like the pull-tab, is also made from aluminum.
Aluminum foil, even when flattened is also detectable so, depending on thickness it can be discriminated out. So, the trick is to set your regular Discriminator control to just reject light foil – usually the sort found inside the top of a pack of cigarettes when first opened. So turn on your Sovereign in Disc Mode, and passing the crushed foil slowly over the coil increase the Disc control to where the foil ceases to give an audio response then stop there. You are now halfway to, eliminating two of the chief offending items most commonly found whilst metal detecting. Then, take a pull-tab, and try to use one which you have already found and common to your area, and again just like the foil pass the tab over the coil and adjust your Notch control to tune out the pull-tab. A word of warning here – this can be a very delicate setting as sometimes the point of rejection can be missed at first as it is such a fine set point. The detectable signal can return again as you may have gone past “the small window” of rejection. Try again, and do it slowly until you can definitely hear a distinct break up of signal and reduction of signal response. Be advised there may not be a complete signal null. Instead you might hear just a short clipped, ‘ reject type ‘ spit sound as, you pass the tab back and forth across the search coil. This is your Notch Set Point. This is where you want to be. Now, if you are really adept with your fingers, it is possible to discriminate out more than one pull-tab type at the one set point. That’s it, you are ready to work that beach or park and not have to dig too tabs. You will still dig similar items that do not fall into that conductive band, but will also save yourself somef unnecessary digging. What you have done here is called Partial Notch, as you have chosen to take out a particular width of conductivity at most just one type of tab and possibly up to two. With the Minelab Sovereign this is a fixed and very narrow band. Not so with the Minelab Explorer – it gets better.

Complete Notch Ability

I have shown how the Sovereign Elite Notch Control can be effective but within very rigid parameters. Just a tiny percentage of usable notch ability is achieved which is common to usually just one single item. Imagine having the power of 100% notching abilities, to either reject or accept every item you could possibly wish to find or not find. Is this too good to be true? No. It is not. The technology is already available and is patented, in the popular Minelab Explorer series.

During the summer I was detecting a really large beach. I needed to complete the search and having to wait for people to leave some of the productive areas it had been impossible to cover fully. It was beginning to get dark and I soon found myself alone as time went on. I was mostly interested in finding coins and rings only. If other items were found that was great but primarily I was after the smaller items. I had recovered many coins and square pull-tabs along the beach but in one particular area I dug twenty-four tabs in a row from what must have been an entire case of beer. Normally I would recover every good-sounding signal but that particular evening, time was marching on and it called for some drastic measures to counteract the large quantity of pull-tabs which had been lazily deposited into the sand by the beer guzzling, sun-worshippers.
I engaged the Explorer’s Learn Mode facility and on the spot “taught” it to reject a single square pull tab only, as this was the one and only target type that I did not want to waste any more time on recovering. At the end of the evening’s search I had recovered 147 coins, a 9ct gold ring, two silver rings two watches a Timex and an almost all plastic Swatch brand, two bracelets, various ornate hair clips, numerous toy cars and most importantly, no more square pull-tabs. It was done by engaging the Advanced Learn Reject option and I sized the area of rejection using the smallest cursor size, of which three are available, small, medium and large, which when engaged with the smallest size looks like a tiny fleck of black on the screen. This was enough rejection to eliminate that particular width of conductivity while still remaining sensitive to similar conductivities. If you look carefully at Fig.7 you will see just what that discrimination pattern looked like.
I was quite safe in doing this, as I knew any deliberately rejected targets would most likely be new (or fairly recently) discarded square pull-tabs from what appeared to be the two top-selling beverages, one a beer, the other a cider.


Analysis of pull-tab rejection and understanding eddy current flow

On another experimental search I created a different pattern altogether to eliminate all pull tabs, including the old beaver tail type, and the real culprit in my opinion, the tear-drop portion from this type pull tab, the ring part from this tab (can be found complete or separately), and the new square tabs. Here is how it was done. At a depth of about 3” an example of each was buried in the wet sand at the location to be searched. They were spaced well apart so there was no chance of the Learn facility ‘relearning’ if the signals from each overlapped. See Fig. 8 to see the rejected pieces. The important thing was to select the smallest cursor size to minimise the rejection area (darkening) of the screen. Here is why. With the small cursor, and using broken or folded over tabs, and other different styles of round and square pull-tabs, the detector may take a few moments to analyse and learn all the curved angled areas and shapes which can cause different types of eddy current flow in those items. With a single pull-tab you are not talking about a single eddy current flow – you will have the inside and the outside and all the different shapes within the tab. You can very easily demonstrate this yourself by passing a square tab over the Explorer’s coil and listening to the tones heard. There may be a few as the machine analyses and sees the different shapes contained within that piece. It may take a while to learn the signatures of multiple targets using the small cursor and when done properly will produce tiny black flecks which all join up when the Learn Facility is disengaged. You will notice that, using the medium and large cursor formats, items may be learned quicker. That is because more screen area is being rejected. But, for this type of searching, the small cursor is recommended. See Fig. 9 to see the small cursor pattern, which was created to reject the pieces shown in Fig. 8

Important points

Use of the small cursor allows very small bands of conductivity to be rejected while still remaining sensitive to similar bands. If you examine the patterns in Fig. 10 & 10a you will see exactly the same pattern I made with the small cursor in both the medium and large format. You will see the considerable differences in “lost” areas and can appreciate why there is a possible risk of rejecting low conductive targets utilising the larger cursor formats. At other times, use of the large cursor format is beneficial when the desire is to reject large bands of ferrous targets or something else that you do not want to find.
The other very important aspect to remember is the Smartfind cursor. It is free to move around the entire screen. If you notice the size of the Smartfind cursor, you will see that it is quite large in comparison to the blacked out area in Fig. 9. This means even if you have chosen to “lose” a segment of conductivity, if a target is located which falls outside that particular band, it will still register with an audible sound as you have not selected to fully remove that whole band of conductivity but just a tiny portion of it. If the Smartfind cursor moves over to register a new target even though a certain portion of that new target has been discriminated out, there will probably be a clear space in the Smartfind cursor area and this is open to accepting that target which bears a resemblance to the conductivity of the one you chose to reject. That’s the trick to predetermining the signal characteristics of the pull-tabs, which you want to discriminate out. If a target is very similar to a particular signature, but at the same time different enough for the Explorer to recognise this, then you could be rewarded with another ring.

Another important aspect of creating “Disc Patterns” is, one is best advised to do this directly on the soil or sand of the areas to be searched. My test targets were buried three inches down into the wet salt sand and the Explorer when learning these targets was at the same time ground balancing to the salty conditions and, setting its usable semi automatic sensitivity accordingly to that particular beach. If I had later stopped at a grass park and gone straight in with the saved disc program used on the wet sand the possibility exists it might not have worked as well as it had done at the beach. This, because the matrix of the soil surrounding targets would now be different possibly due to a different form of mineral content over that of the salt wet sand? The detector had considered the targets and the wet salt sand together. The equation could change over different soil types in the ground. It appears the tendency is for conditions to change more quickly over soil than a salt wet sand area where conditions tend to remain much the same, especially if one searches parallel to the tide line.

Final word

Experienced detector users usually use very little discrimination. If junk becomes an irritating aspect of any search then a saved discrimination pattern as I have described here can be made up. There are times when they can come into play if a particular non-desirable target becomes bothersome.
The possibility exists that by rejecting a larger area than necessary other desirable items might also be lost. With the Explorer series the chance of this occurring can be reduced dramatically by utilising the Resize cursor option in Advanced Learn and the excellent 28 Multi Frequency advantage which can produce the same amount of tone variations and the brilliant Digital ID screen which shows both FE ferrous and CO conductivity content of all targets (Minelab Explorer ll only)
With experience gained through many hours of detecting, it is surprising how one can become very tuned in to exactly which targets sound ‘iffy ‘ or worth recovering. Systems or programs are not foolproof – they can sometimes be open to inaccuracies, which might be welcome or unwelcome. Perhaps due to the target’s shape, angle at which it is buried, or how corroded it has become due to length of burial i.e. long or short duration etc.

To conclude, I have shown throughout the article that it is indeed possible to completely discriminate against nearly all types of pull-tabs (I am sure there are other types out there that I have never seen) by using either regular discrimination, notch reject or creating custom-made discrimination patterns. However, I have also advised that prudent use of discrimination is advisable. The option to hunt and possibly never recover another pull-tab is available.
You could use those options if you would like to dramatically reduce the amount of pull-tab recoveries made.

Finally, as the saying goes, “the truth is out there.” The real truth is, so are the rings: lots of them. They can be found virtually any place? Perhaps after reading this article and trying out some of the suggestions contained herein, your ring recovery rate might increase as, you now know how to leave a lot more of those pull-tabs behind.


© Desi Dunne

Guide to the illustrations.
Fig.1 – 4, various silver colored tabs
Fig.5, - various colored tabs
Fig.6, - Sovereign Elite front panel
Fig.7, - single square pull-tab discrimination pattern using small cursor size
Fig.8, - various rejected pieces of tabs
Fig.9, - small cursor reject pattern rejecting pieces shown in Fig. 8
Fig.10, - medium & large discrimination patterns which are larger versions of the pattern shown in Fig.9
Fig.11, - gold rings found



Edited 2 time(s). Last edit at 01/16/2019 11:05AM by Des D.

Now that was a LOT of information Des..... which is still very useful when working trash with the FBS machines and can be applied with others. Sometimes pattern hunting when working with limited time or recent drops (at least for beach hunting) can be very effective over.... dig it all.

Nice read, Des,
HH
MIke

I take it you guys have never read Tom's take on pull tabs. Look at his story.

I take it you guys have never read Tom's take on pull tabs. Look at his story at the fount of his forum.

Desi, just bustin on ya ... because you put a period/decimal after the 3 instead of a comma. Thanks for the write up!

It seems that every time I go hunting, I can never just simply 'hunt' and enjoy a basic coin-shoot. Rather, I always turn it into a research project or a experiment. This usually includes spending large amounts of time recovering many 'trash' signals. Occasionally, my hunting partners will wax me in the volume of "keeper" finds, then commence boasting - to playfully ruffle some feathers.

It was late in 1999 when I took on such a project. My quest was to find; "At what depth was the 1962 dirt strata". This was the year that a detectorists nightmare debuted; the aluminum pull-tab. --- Thousands of targets were dug and depths were carefully measured. Initially, I thought that it would be the coins (because they are dated) that would give the best and most conclusive data for dating the depth stratums -- especially from the coins that were nearly uncirculated when they were lost. However, unexpectedly, the pull-tab with its many differing varieties provided the most precise data. Some certain style pull-tabs had a life-cycle of only a few weeks. It is safe to assume that these specific pull-tabs were lost during their active life-cycle; an eight month old RC Cola may not taste so good --- expiration date aside. The sink-rate of differing density metals must be taken into consideration along with ground moisture, cumulative foliage, grass root structure, dirt density/composition, ground activity and any other data altering occurrences, so as to remove as many variables in order to ascertain quantified research validity.

Conclusive analysis was achieved in May, 2000. The 1962 strata of dirt was located at 9.22" deep. Several places in Florida, Georgia and California supported this data. In some areas, the sink rate was worse and in other areas the soil provided greater stability with the older targets being located at shallower depths as a resultant. This sink-rate data represents the median average. At the time of this writing (April, 2006), I surmise the 1962 median average soil strata is at approximately 9.5".

What good is this data? Well....... many decisions & conclusions can be formulated with such information. In bullet form:

* Use a deep seeking unit.
* Find areas where soil has a slower sink-rate.
* Recover only the deep targets under these high sink-rate conditions.
* Use a large coil in areas where targets are sparse.
* Recover the pull-tab signals at the pre-1962 dirt depth strata's.
* New England States are lucky! (Slower sink-rate dirt).
* Sink-rates can vary dramatically from site-to-site and State-to-State.
* A superior detector may not be the answer.
* You may experience that 9 out of 10 places you hunt will produce
nothing old -- only clad coins at deeper depths.
* Promise yourself NOT to get discouraged.
* Accept the fact that many premium looking, 'prime sites' have
sink-rate soil failure conditions.
* You may experience conditions where dirt mineralization is so
severe that even the top performing detectors,
multi-frequency or otherwise, may not be able
to detect a coin exposed on the surface of the ground.
* Educate yourself FIRST about 'dirt conditions'
---then, secondarily about top performing detectors.
VERY CRITICAL order-of-events!

Hunt Wisely!
Happy Intelligent Hunting
Thomas J. Dankowski
thomas@dankowskidetecting.com
.
There ya go.....

My report was written as far back as 2003 and published in 2004.
But, thus far NO DETECTOR manufacturer has managed to eliminate the 'pull tab resembling gold ring' problem.
Will any company ever manage it?



Edited 1 time(s). Last edit at 01/18/2019 07:37PM by Des D.

Des..... with the way metals change based on conditions, coil size, minerals, near targets, variations, and angle...... not likely as it stands now. Like i said with my test...... out of a little over 100 gold pieces of jewelry.... 9 hit as pull tabs in that nickel range on a Nox. Then .... you have to deal with the broken ones. Until we get a picture of what we are digging....... i think we will be digging..... just no short cuts to digging just gold. Even the possibility of widening that specific range..... i think wed be hunting just ring size gold since they have a difference response than earrings and such.