Friday, July 8, 2016

7/8/16 Report - Halo Effect, Ground Effects, and Notes On Testing Your Metal Detector. Kirlian Photography.

Written by the TreasureGuide for the exclusive use of

Kirlian Photograph of US Half Dollar.
Source: See link belwo.

Yesterday I discussed air tests and ground tests and pointed out one common problem with both of those kinds of tests.  That problem was the say the coil or target was moved.  Today I'll discuss a completely different problem.

If you understand these problems, you'll also have a better understanding of how your detector works, and as a result, be able to use your detector more effectively in the field.

People often bury for ground tests. Some create test gardens.   I'll maintain that very similar results can be obtained by simply laying the target on the ground and then raising the coil above the target.  Little is gained by burying the target.  When the ground is neutral, it can end up being nothing more than a glorified air test.  When the ground isn't neutral, it can end up being worse than an air test for reasons I'll discuss below.

One reason, but not the primary reason, is that the soil is unsettled and loose, but also the object can be standing on end or in some other odd position unless care is taken to position it.  As I've shown in the surface angle of the target is an important factor.  A coin standing on end, for example, will typically give a small and uncharacteristic signal.

When a target is buried for a metal detector test, it is not like the typical target you most likely find during a hunt because during an actual hunt the target has typically been in the ground a while.  As a result there is what is called the "halo effect."

The "halo effect" theory holds that buried metal objects have an ionization "halo" that increases their apparent size to a metal detector searchcoil.  This makes the objects detectable at greater depth.  In other words, according to this theory, long-buried metal objects have something you cannot duplicate with a recently-created test garden.

It takes a while for the halo to form, and the halo effect is greater with objects that have been buried for a longer time.  The halo effect is also increased in certain environments, such as saturated soil.

Here is a web site that discusses the halo effect in detail.

Remember also what I've said about compacting sand and soil.

The lack of a halo effect is not the only problem with newly buried targets.  When there is any degree of soil mineralization or conductivity, digging a hole creates discontinuous ground conditions that a metal detector will try to adjust to.  Such disrupted sand or soil will cause your computer to adjust and will often cause false signals, and often a reduction in depth.

It is not unusuaal to detect a coin in black sand, then dig a hole only to find that you can no longer find the target.  In some cases that is due to the difficulty your detecdtor is having in adjusting or interpreting the ground conditions created by the disrupted matrix created when you dug the hole.

OF course different detectors will adjust differently and different settings will also affect how your detector adjusts to those circumstances.

Perhaps the easiest demonstration of this is in black sand at the beach.  The next time you encounter black sand give it a try.  Dig a hole in a concentration of black sand.  You very well might find that you get a signal from that hole.  If you toss a coin into the hole, you might have difficulty detecting it, especially at depth.

It is very much like when a wave comes washes over dry or partially dried sand at the beach.  There will be a line between the newly wet salt sand and the dryer sand.  Sweeping across that line can cause a false signal or a reduction in detecting depth as your detector tries do adjust to the difference.

Regarding the halo effect, here is a summary of three main points from the previously referenced web site.

1.  Test gardens aren't much good unless they are old because the Halo Effect hasn't formed on newly buried objects.  New test gardens are not much better, if any, than an air test.

2.  Noble metals ionize in the ground too.

3.  Some environments create the Halo quicker than others, such as moist and acid environments.

My main point is that not only will the halo effect not be present when a target is newly buried, but there are also other problems, including the fact that the soil matrix has been disrupted.  In some circumstances, that can be a very significant problem.  That will make ground test results different from what you would get from a naturally buried and settled object in the field.


That reminds me of some Kirlian photography that I used to do.  Kirlian photography allows you to capture an image of elecrical fields around an object, very much like the halo effect.

Here is a little about that.

In 1939 Semyon Kirlian discovered that you could photograph the aura of an object by placing the object on a photographic plate in a high-voltage electric field. The photographic image looks like a colored halo or coronal discharge.

Images created by Kirlian photography were mistakenly thought by some to be a physical manifestation of the spiritual aura or "life force."  What is actually recorded is the result of natural phenomena including pressure, electrical grounding, humidity and temperature. Changes in moisture barometric pressure, and voltage will produce different 'auras'.  So what is actually seen on the photographic plate is gas ionization around the object - living or not.  

Here is a link where you can read more about Kirlian photography and auras.

And here is a link where you can find the photo of the coin shown above plus a variety of other Kirlian photography. 

And here is the Kirlian photography system that I once assembled in an old brief case.  I did a post about that some time ago.

Kirlian Photography System Assembled in Brief Case

Inside the case (top photo) you see a variable voltage trasnformer and a high frequency induction coil.

On top of the case is a metal electrode plate and a glass dielectric plate.  The glass plate is placed over the electrode plate, then Polaroid film places on top of the glass plate and the object to be photographed placed on top of the Polaroid film.  Then, while in a completely dark room, push the button (white seen through the hole in the case) and the aura is created and picked up by the film.

Unfortunately I can't find any of the old photos I took with this equipment.  I should be able to make some new ones once I warm up this old system.

I intend to get that old system up and running again and take some more photos of coins and other targets.  


I wanted to express my deep felt sympathies for those who were killed yesterday as well as their families.  It is too bad what has become of our country.


On he Treasure Coast expect more hot weather and calm surf for days to come.  There is not tropical activity to watch either.   Low tide will be around 5:30 today.   There will be some slightly negative tides.

Happy hunting,