Metal detecting in the rain, or after a good rain, is a bit messy. You wonder if you should even try. There are good reasons to, and we’ll help you understand why. Right here.
The community is divided on whether metal detectors work better on wet ground. My experience, along with a lot of online research, favors “yes, metal detectors actually work better on wet ground.” The reasons for that are quite interesting and include topics like improved conductivity and the debated existence of something called “the halo effect.”
There’s also something intuitive about wet ground being able to improve detection capability. Almost like the fact that (non-pure) water is a conductor of electricity… you can imagine that the coil signals sent into the ground from a detector somehow benefit from the wetness. Well, maybe… let’s see how this all works.
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Opinions and Science
Most opinions out there, based on actual metal detecting
experience, say that you can generally get better performance and even detect deeper targets when the ground is wet.
The most technical/scientific reason, though somewhat debated, is because of the “halo effect”
The halo effect presents a bigger target to the detector. In other words, the buried object tends to sound larger than it is. Most people agree that it’s because of target oxidation over long periods of time as in years, decades, and longer.
You’ve seen rust on iron, you’ve seen green on copper, and perhaps a tarnish on silver. Those are forms of oxidation.
- Some people don’t believe silver, copper, and gold (all noble metals) can oxidize well enough over time to produce this halo. If you want to dig into some science on that, see this article.
Over time, with ground moisture seeping deep into soil, metal objects can oxidize. As the rust on iron or tarnish/green corrosion on coins slowly grows, that oxidation leaches into the surrounding soil. This then looks like a larger object to your detector and becomes easier to locate. At first…
Then the Large Target Disappears
Interestingly enough, once you dig for the object and disturb the particles of dirt, you effectively collapse the halo. When you go back over the hole with your detector to see if the target is still in the ground, you may not get a signal anymore. With the smaller footprint, your detector’s sensitivity and/or discrimination is either showing a smaller target or isn’t allowing you to pick it up at all.
What to do: You get an indication of a large object and dig into the soil for it, but don’t find it. You scan the hole again but the signal is gone. The halo has collapsed. However, don’t give up. The small object could very well be in the ground, just a bit deeper than you dug. Go after it.
The Battle of Iron in Wet Soil
The halo effect isn’t always on your side, though. Iron decays the fastest and therefore has the largest halo. Copper gets a good halo, silver much less, and gold gets no halo (maybe a miniscule one if it’s not pure gold and has impurities on the surface.)
Therefore, in wet soil your detector would respond to the iron better than the silver and could actually mask the presence of the silver object. If you were hunting old silver coins or relics in iron infested ground (perhaps there are a lot of nails), you’d be better off hunting that area in dry conditions where your detector can more easily discriminate the difference between the iron and silver.
So when you already know that the ground has iron in it, wait for a few days after it rains. Experience has shown that the separation between signals becomes much more obvious after the ground dries out.
What is “wet ground” anyway?
It depends. Moist ground is good, but a soggy swamp-like consistency is too moist. It’s a judgement call of course, but I like to think of it this way to judge if the halo effect may play a part in the day’s hunt.
If I dig up a plug in the area I’m hunting and the dirt below the grass crumbles, seems grainy, and falls off the plug, it’s probably not moist enough to take advantage of the halo effect.
If I lift out the plug and it drips water, then it’s probably too moist. I’d look for in-between, where the dirt holds together and has a darker, richer color compared to dry, loose dirt.
- As always, remember that factors like minerals in the soil, how compacted it is, and the ground’s composition (red clay for example) also play a part in the outcome of your hunt.
Metal detecting is a hobby of experimentation,
the more you do with it, the more you learn.
Preserve the hobby for others: In terms of being a good ambassador for the hobby, remember that digging in wet soil also greatly reduces the chance of leaving dead spots in the grass. Too much of that and you run the risk of getting access to parks and other good places shut down.
Pros & Cons Regarding Wet Ground
Do metal detectors work better on wet ground? Yes, overall. Yet some folks do have personal experience to refute that.
Here are some factors to consider:
| Pro | Con |
| Softer ground, easier to dig | Need a waterproof coil unless it’s raining, then a waterproof detector is bestWet soil isn’t as likely to leave a brown spot where you dugGloves and knees get soaked, mud sticks to things, harder to pick up coins with glovesLow mineral dirt can enhance detection depthSaturated dirt with high mineralization can “activate” the iron in the dirt (the halo), reducing (masking) detection of deeper items, impacting identification. |
| Halo Effect: over time, moisture leads to target oxidation and increases the conductivity of surrounding soil (until disturbed) | Halo effect is well accepted, but also debated even to the point of using atomic-level calculations, units like moles, and Avogadro’s constant. |
