Guide to Building a Metal Detecting Test Garden

Kevin Hoagland

Huge area that I meticulously laid out before planting a single target. All corners have GPS coordinates. If you look closely at the northeast corner, you can see a small wash; during

the monsoons it ages the locations with every rain. »

Over the years there have been thousands of discussions bordering on arguments from detectorists on depth, signal strength and target response, you name it. But one thing that all of us coil draggers agree on is that bench air testing a metal detector doesn’t give you real information, none at all. I can hear it now, the naysayers that say air testing is a good way to

(insert your answer here), but I can assure you that with 50+ years of detecting under my coils, it doesn’t. Let me ask one question: When was the last time you found a gold nugget or anything floating above the coil?

Look, I get it, and I do swing things over my coils as well — but not to test anything else other than if I am getting a good audio response, that’s it.

How do you test your detector’s responses properly? A test garden is the only answer. And there are two types that I will describe, and I have both. Now before I go any further, there are some do’s and don’ts about building a test garden:

X X X DO’S

Collect material everywhere you detect to add to your garden. Black sand, hot rocks, cold stones, iron soil. If it has ever given you a problem out in the field, it goes into the garden.

Maintain your garden. Water it every time you go there (after you have used it for testing). Watering the soil will help the garden mature quicker. Not fast, just quicker. Especially if you have junk irons in the ground, watering will help with the oxidation process and speed up the leaching into the ground.

Take your time building your garden. The more time you spend, the better the results.

DON’TS X X X

Use gold for your targets. Use lead, because it’s close enough to give you a pseudo gold signal and you will never be tempted to dig it up.

Put your test garden in a place where a detectorist can stumble upon it and dig your targets out. Instead, put it in a no-gold area that no one would ever think about detecting.

Tell anyone where your test garden is located. I have one that is almost 30 years old, and no one knows where it is.

Expect that your test garden is going to give you everything you need to know right off the bat. A nugget has been in the ground billions of years; you are going to have to patiently wait for it to mature and to give you the right balance of target to ground responses.

WHAT YOU NEED

Pick and shovel and a will to dig.

Soils from the worst areas that you have worked; a five-gallon bucket is a good start.

Every target will need a five-gallon bucket (remove the metal bail). If you are building a deep test garden, the targets will be below the height of a five-gallon bucket and will need two buckets per test piece.

Plastic food storage containers.

Paracord or something to use as your surface markers attached to the target container. If you are using paracord or any type of rope, know that it will rot.

Lead targets. Old tire weights are what I use, minus the steel tab that attaches the weight to the rim.

Now Let’s Get to Planning and Building a Generational Test Garden

Planning a test garden is important. You need to give thought to the targets, weights and spacing. A good test garden takes up some ground, a great test garden takes up a lot of ground. To find the perfect spot will take a little time and you need to know beforehand how many targets you will be putting into the ground. My current big garden hosts 50 targets, with each one being no closer than three feet away from each other. Now you can get away with two feet easily, and there is no need to make your garden linear. Mine isn’t. It is four rows of 12 and then two big deep target standalones for big coils. For the most part you can build a great garden with 15 to 20 targets. Here is what I suggest for a 20-target garden: ¼-gram at 2-4-8 inches, ½-gram targets at 5-8- 10 inches, 1-gram at 4-8-12-14 inches, 5-gram targets at 6-10-14 inches, 1/2-ounce at 8-12-14 and 1ounce at 8-12-16-18. All of these are based on using a pulse induction detector and different coils. If you are building a garden for VLF detectors only, take 20%+ off of the depths I’ve listed. Of course, coil sizes and VLF frequencies have to be considered as well. If you have a Garrett 24K or a Gold Bug 2 with small coils, you will not be reaching almost two feet into the ground with that coil on sketchy ground.

I wrote about smelting my lead to make test pieces. It is just as easy to use a hammer. Plus, you don’t have to deal with all the PPE I end up using. »

With a little time and some imagination, you can make lead into some really good looking ledgeets, (lead nuggets) in shapes like gold nuggets. »

Planting the Garden:

• For each target dig a hole that the five-gallon bucket will fit into with the top of the bucket just below the surface.

• Drill a lot of holes in the bottom of the bucket to allow water to seep through. This is important, as the soils in the bucket need to be able to react like the surrounding soils for moisture content.

• In holes where the target will be deeper than the bucket, cut the extra that you need from another five-gallon bucket and epoxy it to the top bucket. In these holes you can cut the bottom out of the upper bucket if you want or drill more holes in the upper bucket and in the extension bucket.

  

  Using anything other than a flat rock will make the ledgeets realistic. »

  
  

   

  
  

• For the lead targets, if using tire weights, cut the steel tab away from the weights, then cut them to a weight more than what you need for each hole. I used a map gas torch to melt the lead ONLY into a sand mold. Melting lead is not the best of ideas and I did wear a respirator designed for that. The other and most likely a better choice I feel works just as well, beat the lead into a nugget with a ballpeen hammer. If you have to beat two pieces of lead together that’s fine, most of the time you can get them to merge together; if not, safely use a torch to join them. After they are beaten down, weigh and trim them to the proper weights for your garden.

Buckets, lots of buckets. Pull off the metal bail and bury them just below ground level. I also like using these bottles. Great sealing screw-on lids and more than enough room for larger test pieces. I buy these new from any medical supply. »

Bury your buckets first and please make sure that you are logging these into a journal so you will remember five years from now what targets are in what holes. Once in the ground, fill

them with the material you have collected and compact the material as you go. It does not have to be a tight compaction, just enough that when you water the holes for the first time, they don’t sink more than an 1/8 of an inch. While you are filling the holes, when you get to the depth of the target, put the target in the plastic container, fill it with the dirt, tie your marker string to it and continue to fill the bucket, making sure that you do not bury your marker string. Again, unless you are using something like braided fishing line, it is going to rot within a couple of years, more than enough time to know if your targets have sunk or lifted.

Try to hammer out the lead on a rock that has character, makes it more like gold.

»

NOTE: Hot rocks and cold stones need to be close to the surface where you found them, put those in last just below the surface and have some on the surface.

You can swing your coil over each target to make sure that you hear them; if not you can leave it alone or move it up a bit. I generally leave them alone. It is a great way to test different

settings and coils on a detector. Make it a challenge to find those targets. Plus, if you want to head-to-head test your current detector against another one, it is a great tool.

When you are done, flood water each of the buckets and make sure that you are using enough water to get the buried targets wet. This settles the soil and helps start the oxidation process of the targets.

And before you walk away completely, mark the spot on a GPS. Don’t use something like it is set up 50 feet to the east of the big tree.

Now go away for a few months and let the garden begin to mature.

That’s it. Yes, it is a lot of work but the reward of having a true-to-the-ground test garden is worth it to me and many, many others of us out here who can and do hear the subtlety of many targets and the ground. There is no set sound that a nugget makes, just like there is no set sound that the ground makes, and being able to really hear everything allows you to be able to tune your detector and you to the ground.

Kevin Hoagland is the Executive Director of Development for the GPAA and can be reached by email: khoagland@goldprospectors.org.