Can Metal Detectors Detect Plastic?

Ever buried a toy in the sand and wondered if a metal detector could find it? Dive in to uncover the surprising truth!

Can Metal Detectors Detect Plastic

As I was building my brand around metal detecting, several people asked the same question through my emails and on my social media accounts.

 “Do metal detectors detect plastic? Or, more specifically, does plastic hinder the ability of metal detectors to function properly?” 

Even though it might seem obvious that metal detectors can’t detect plastic, I took it upon myself to find more information on this topic to educate you. 

And now, I have some interesting facts and information to share with you

So, let’s find out, Can metal detectors detect plastic?

No. Metal detectors cannot detect plastic since metal detectors are designed to detect ferrous and non-ferrous metals. As plastic doesn’t fall into any of these categories and can produce a metallic signal within itself to trigger the metal detector’s sensors, metal detectors aren’t capable of detecting plastic. 

But that’s just a quick snapshot!

So, in this article, I will be talking more about this topic and interesting findings about plastic and metal detecting. 

Hang around till the end and find out more about the interesting connection between metal detectors and plastic or should I say the lack thereof. 

Without further due let’s jump straight in!

Plastic items that can be found when digging ground
Plastic items that can be found when digging ground

Do Metal Detectors Detect Plastic?

Metal detectors aren’t capable of detecting plastic because Plastic doesn’t fall into any category of metal. 

Metal detectors are mainly designed to detect metals. These metals could be of two types ferrous metals and non-ferrous metals. 

Whether it is a ferrous metal or a non-ferrous metal metal detectors work in the same in detecting these. 

Metal detectors produce an electromagnetic current that travels through the metal detector into the soil. Then when it reaches the soil it spreads and travels until it finds something metallic. 

Upon striking something metallic, the electromagnetic radiation generates a counter-current in this metal known as an eddy current. 

This eddy current will then travel back to the surface of the earth. 

This traveling eddy current will be detected by the magnetic coil of the metal detector. Which is then depicted on the screen as a visual signal or as an audio signal by an alarm. 

This is the basic principle that metal detectors work in. so, I hope this helped you to understand why metal detectors can’t detect plastic. 

As plastic isn’t capable of generating the counter current which is the main thing that determines the founding of a metal, plastic is undetectable by metal detectors

More so, metal detectors ignore plastic-like non-metallic things in the detecting field, focusing more on metallic substances and their signals.  

Did you know fact about Plastics
Did you know fact about Plastics

Why Metal Detectors Can’t Detect Plastic?

Metal detectors detect metal based on the electromagnetic induction of the particular metal. 

As I explained earlier plastic like non-metallic substances isn’t capable of generating that electromagnetic induction to trigger the metal detector. 

Metal detectors are designed to detect high-conductivity materials like metals

That is why your metal detector is very successful in finding Iron, Copper, Aluminum, Gold like substances but even when trying to detect something like Lead it struggles.

Even though lead falls into the category of non-ferrous metal, and it has electromagnetic induction, the power of that electromagnetic induction is very little. 

That is why your metal detector struggles in detecting stuff like that.

More so to a metal detector to detect a metal the induced electromagnetic radiation should be high. Higher the induced electromagnetic radiation more the chances of identifying that metal. 

As the magnetic coil of metal detectors is designed to detect the differences between electromagnetic fields. When a sudden increment of electromagnetic radiation is detected by the magnetic coil it signals the user.  

Now you might be thinking if magnetic coils are designed to sense a difference why can’t they detect a drop of magnetic induction? 

Because the magnetic coil constantly releases electromagnetic radiation, a drop is not usually detected due to the same amount of charged electromagnetic radiation always dissipating from the coil. 

Even though you used different settings like adjustment settings and sensitivity settings, still you might not be able to detect plastic. 

Plastic doesn’t have electrical conductivity, which makes it harder for metal detectors to detect a significant difference in the magnetic field to produce a signal. 

Features of Plastic items
Features of Plastic items

Can Metal Detectors Detect Through Plastic?

Metal detectors are sometimes capable of detecting through various obstacles. And that is the case in plastic substances too. 

Sometimes the electromagnetic current of metal detectors can pass through the plastic and detect things underneath them. 

For example, imagine that there is an iron piece wrapped in plastic sheets about 8 inches below the surface of the earth. 

Your metal detector is more than capable of detecting the signal of this iron piece due to various factors. 

First of all the iron piece is a large block and it is one of the highest electrical conducting elements, which makes it easier to detect by the metal detectors. 

And it is placed at an ideal depth from the surface of the earth which makes it even easier to find. 

Then it is wrapped in a plastic sheet which as we know isn’t the thickest material out there.

So due to these combined factors, the lock of iron below 8 inches from the surface is easily detected by the metal detector. 

Plastic toy that found during my journey of metal detecting
Plastic toy that found during my journey of metal detecting

Here are the factors which will affect the ability of metal detectors to search through plastic,

Type of Plastic

Plastics are not conducting materials that are not able to produce an electromagnetic induction

But lately, companies are trying to make plastics that are blended with metallic elements to increase the durability of the plastic. 

These types of plastic could alter the signals of the metal detector and portray difficulty in detecting what’s underneath the plastic. 

The Thickness of the Plastic

The thickness of the plastic is the most important factor, which would determine if the incoming radiation is dispersed are easily passed through

If the plastic is thick it will alter the electromagnetic radiation of the metal detector and make it harder to detect. 

But if it is a thin plastic like a plastic sheet, it will allow the electromagnetic radiation to pass through with minimum disturbances and allow the detection of material below it. 

Sensitivity of the Metal Detector

The sensitivity of the metal detector also influences the permeability of electromagnetic radiation through the plastic

If the metal detector is having high sensitivity settings that can recognize even a smaller piece of metal, it has a higher chance of passing through plastic rather than ta lower sensitivity metal detector.  

Apart from these factors detecting through plastic could lead to false narratives. Where it might signal detection of metal when there is not and not detect a metal item when there is one. 

These are known as false positives and false negatives respectively. So, when we are detecting through plastic, we have to keep in mind that the result will not always be accurate too.  

How to find plastics
How to find plastics

How To Identify Plastic Items 

Identifying plastic items is an easy task when they are above the soil. 

But when they have been under the soil for quite some time, it could be hard to determine if the specific item is plastic or not. 

Imagine if you uncover some plastic from metal detecting while digging up to find another metal or any other way, here are ways you can check whether it is plastic or not,

Visual Inspection

First of all, thoroughly look at the item and try to determine whether it is plastic or not. You can try with washing the object and removing the dirt to further inspect. 

This is the most basic method and mostly this is enough as plastic is degradable. And if this isn’t here are some other ways,

Plastic cup that found during my journey of metal detecting
Plastic cup that found during my journey of metal detecting

Flexibility 

Try to bend the found item slightly, if it is flexible there are only two possibilities that it might be. Either it is plastic or aluminum. 

Now feel the item uncovered, if it doesn’t feel metallic it is a plastic item. You can try to tap on the object too, if it gives out a dull sound that is confirmation of it is plastic. 

Burning

The next method will surely confirm whether it is plastic or not. Try to break a small piece of the found item. 

Then expose it to a flame, if it is a plastic item, it will burn out with a significant plastic smell.

If it is hard metal it will not be affected and if it is a soft metal, it will melt but with no significant smell. 

Plastic bag that found during my journey of metal detecting
Plastic bag that found during my journey of metal detecting

Other Methods

Other methods you can try to confirm whether it is plastic are, 

  • After cleaning the finding try looking for the RIC (Resin Identification Code) in the Plastic. This usually appears in the bottom of plastic within a triangle
  • Try putting it in a water container. As plastic is less dense than water it will float on water
  • If you want to confirm further and see what type of plastic is the finding, you can always carry out lab chemical tests. These results will confirm the exact type of materials the found item is made of. 
Plastic military box that found during my journey of metal detecting
Plastic military box that found during my journey of metal detecting

How Do Metal Detectors Work? 

Metal detectors are designed to detect metals. These metals can be either ferrous metals or non-ferrous metals. 

Metal detection works according to a special principle that allows the metal detector to detect items that are covered by other objects. 

Metal detectors have a coil of wire loops inside its body. 

These wire loops pass through an alternate current, which forms an electromagnetic field around these wire loops.

This generated an electromagnetic field that send out waves to the surrounding area. 

When these waves are struck by a metallic element in nature it causes the metal to form a counter-current in that material known as eddy current.

These eddy currents are capable of creating their magnetic field opposing the original electromagnetic field.

This difference in the electromagnetic field is then detected by the coil

Then the control unit which is intact with the coil amplifies this signal and turns them into audio or visual signals.

These audio or visual signals are then released, which makes the user aware of something underground. 

Plastic bottles that found during my journey of metal detecting near river
Plastic bottles that found during my journey of metal detecting near river

What Can Metal Detectors Detect?

Metal detectors are designed to detect metals. These metals could be ferrous or non-ferrous.

If something is having electrical conductivity it is detectable by a metal detector. 

Here is the list of things that can be detected by metal detectors,

Highly DetectableDetectableNot Likely to Detect
IronMetal objects and artifactsEx: Coins, Jewelry, Metal Buttons, Keys, BucklesPlastic
SteelArcheological ItemsEx: Historical ArtifactsWood
NickelNails, Screws, and FastenerGlass
Cast IronElectronic DevicesCeramics
CopperPackaging MaterialsEx: Aluminum foil
AluminumStructural MaterialEx; Metal pipes, wires
BrassHidden weaponsEx: Knife Blades 
BronzeMetallic Trash Ex: Bottle Caps
GoldMinerals and Natural deposits
Silver
Zinc
Lead
Tin
Alloys
Tip for finding plastics on ground
Tip for finding plastics on ground

Can Metal Detectors Detect Through Plastic Bottles

Yes. Metal detectors can detect metal objects through plastic bottles

The effectiveness of the detection will be dependent on factors like,

  • Size of the metal object
  • Metal composition
  • Bottle type
  • Bottle thickness
  • Sensitivity of the metal detector
Tip for finding plastics
Tip for finding plastics

Can Metal Detectors Detect Plastic Flasks

No. Metal detectors cannot detect plastic flasks

Plastic flasks are made out of non-conductive material, so it is unable to produce an electromagnetic current which will help the metal detector to identify it as a metal. 

Therefore, plastic flasks are undetectable by metal detectors. 

That’s it folks! Now you know exactly whether can metal detectors detect plastic and how metal detectors work when detecting metals.

Plastic flask that I found during my journey of metal detecting
Plastic flask that I found during my journey of metal detecting

Around 50% of the plastic produced globally is used for single-use purposes and is discarded within a year of its production.

plasticoceans.org

So, let’s answer some frequently asked questions.

FAQs

Can metal detectors detect metals through plastic barriers?

Yes, metal detectors can often detect metals through plastic barriers, with the effectiveness depending on factors like the metal’s size, its composition, the plastic’s type and thickness, and the detector’s sensitivity.

How can I identify if an unearthed item is plastic?

To identify if an item is plastic, visually inspect it, check its flexibility, or expose a small piece to flame. If it burns with a plastic smell, it’s likely plastic.

Why do some metals, like lead, pose a challenge for metal detectors?

Even though metals like lead have electromagnetic induction, its strength is relatively low, making it harder for metal detectors to detect when compared to high-conductivity materials like iron or gold.

Did I cover all you wanted to know about: Can Metal Detectors Detect Plastic?

In this article, I’ve deeply discussed can metal detectors detect plastic and why metal detectors are unable to detect plastics with the exact procedure hw metal detectors work.

Metal detectors are designed to detect metals through electromagnetic induction and cannot directly detect plastic, as plastic lacks the necessary metallic properties to generate a detectable response.

Furthermore, I’ve answered some frequently asked questions as well.

Thanks to my research I was able to answer the questions I got about plastics which I mentioned in the first place.

Now you know how metal detectors work like an experienced detectorist. 

Share your knowledge with newbies to educate people about the functions of metal detectors and explain why It’s not the right tool to detect plastic items.

Hi! I’m the treasure hunter and adventurer behind DetectingTreasures.com. I'm here to share my knowledge, inspire your adventures, and provide practical guides to help you succeed in your own treasure hunting journey. Read More...

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