If you’ve ever left your wallet on a café counter, only to rush back and find it untouched, you’ve experienced a small, quiet win over theft. But if you’ve ever worried about someone skimming your credit card in a crowded subway or stealing your passport details from a pocket, you’ve probably considered a blocking card. As someone who’s been in the blocking card supply business for over a decade, I get a lot of questions from customers: “What is a blocking card made of, anyway? Is it just magic plastic?” It’s a fair question—especially when you’re holding a tiny, thin card that’s supposed to block digital thieves from siphoning your personal data. Let’s break down the science, the materials, and why not all blocking cards perform the same way. Blocking Card
First, a quick crash course on how blocking cards work, because their materials tie directly to that function. Almost all modern credit cards, debit cards, passports, and key fobs use RFID (Radio-Frequency Identification) or NFC (Near-Field Communication) technology. These send small radio signals to communicate with card readers, which is why you can tap your card at a gas pump or check-in kiosk. Skimmers (the bad guys) use small, portable RFID readers that can pick up these signals from a few inches to a few feet away, even if your card is in your bag or pocket. A blocking card is designed to block those signals, acting like a barrier between your personal RFID/NFC cards and any unauthorized readers.
Now, the material part. At its core, a standard blocking card has three main layers, and cutting corners on any of them is why some cheap, $1 blocking cards you see online don’t work as advertised. Let’s start with the base substrate, which is the rigid plastic layer that gives the card its shape and durability. This is not the same plastic used for regular credit cards—though you may have seen PVC (polyvinyl chloride) in those. Wait, no: actually, the base of a good blocking card is typically PET (polyethylene terephthalate) or a rigid PVC blend. Why? Because PVC is cheap, easy to mold, and provides a stable foundation for all the layers that do the heavy lifting. PET is more lightweight and eco-friendly, which is why many of our customers ask for it for everyday use. We use a 20-mil thick PET base for our premium blocking cards—it’s thin enough to slip into any wallet, but thick enough to resist bending, scratching, and the occasional crumpling in the bottom of a purse. Cheap knockoff cards often use a thinner 10-mil plastic that cracks if you step on it or fold it in your jeans pocket, rendering the inner layers useless.
The most important layer, though, is the RF shielding layer. This is what actually blocks the radio signals, and it’s where the science gets interesting. The two most common shielding materials are metallic films and conductive inks, and there’s a reason we use a specific type of metallic film in our products. Let’s start with conductive inks first, because you’ll see these on some budget options. They’re made by mixing metal particles (usually silver or copper) into a polymer binder, then printing the mixture onto the plastic substrate. The idea is that the metal particles create a conductive path that absorbs or reflects radio waves. The problem with conductive inks is that they degrade over time. If you rub the card in your pocket a hundred times a day, the ink particles start to flake off, leaving gaps in the conductive layer. After a few months, your blocking card might not block signals at all. Also, copper-based inks can oxidize when exposed to moisture, turning green and losing their conductivity entirely. That’s why many cheap blocking cards stop working long before they’re supposed to.
Our go-to shielding material is aluminum-laminated film, specifically a thin sheet of aluminum with a thickness of 0.009 mm. Wait, let me confirm that—no, actually, we use a 0.012 mm aluminum film, laminated between two layers of PET to protect it. This isn’t the same aluminum foil you have in your kitchen; that’s too thick, and it would make the card bend too much. The thin aluminum film works because of something called the Faraday Cage Effect. Michael Faraday figured out over 200 years ago that a conductive material (like aluminum) can block electromagnetic fields if it forms a closed surface. Wait, but a blocking card is a flat piece of plastic, not a fully closed cage—so why does it work? Because even a partial conductive barrier is enough to attenuate (reduce) RFID and NFC signals, which operate at specific frequencies (13.56 MHz for most credit cards and passports). A properly applied aluminum film can reduce those signals by 99% or more, which is exactly what we need. We tested this in our lab last year: we put three credit cards inside a wallet with our blocking card, and a standard RFID reader couldn’t pick up any data from them—even when the reader was pressed against the outside of the wallet. We also tested cheap conductive ink cards, and the reader picked up two of the three cards from the same distance. That’s the difference in material quality.
But wait, there’s another component we can’t forget: the adhesive layer that holds all the layers together, and the outer laminate that protects the aluminum film. The adhesive we use is a pressure-sensitive acrylic adhesive, which is durable and doesn’t break down when exposed to temperature changes (from a hot car dashboard to a cold winter pocket). Some manufacturers use cheaper rubber-based adhesives that dry out over time, causing the layers to separate. I’ve seen that happen with a customer who bought a 10-pack of cheap blocking cards online—after six months, half of them had the aluminum film peeling off the base plastic. The outer laminate is a clear, scratch-resistant layer of PET that keeps the aluminum film safe from scratches and moisture. That’s why our cards have a matte or glossy finish, and they don’t smudge when you run them through your wallet’s card slot 10 times a day.
Another question we get all the time: do blocking cards block Wi-Fi or cell phone signals? Short answer: no. The materials we use are tuned specifically for the 13.56 MHz frequency band that RFID and NFC use. Wi-Fi is 2.4 GHz or 5 GHz, which is a much higher frequency, and our aluminum film isn’t thick enough to block that. Some customers get confused because they think blocking cards will make their phone signal weaker, but that’s not the case. If someone tries to sell you a blocking card that says it blocks all signals, run—they’re either using materials that are overkill (and would be way too thick) or lying to you. The best blocking cards are frequency-specific, because blocking the wrong signals would be unnecessary and bulky.
Let’s also talk about the environmental side, because more and more customers care about that now. A few years ago, we switched our base substrate to 100% post-consumer recycled PET, and our aluminum film is recyclable through most standard plastic recycling programs, as long as you separate it from the outer laminate. Wait, actually, the outer laminate is a bit tricky—we’re currently working on a new outer layer made from bio-based polyethylene derived from sugarcane, so the entire card will be fully recyclable without any special processing. That’s important to us, because we don’t want our products to end up in landfills when they reach the end of their life (most blocking cards last 5-7 years with regular use, by the way).
I should also mention some red flags to look for when buying a blocking card, because not all products are equal. First, check the material specs: if a card only says “conductive material” without specifying if it’s aluminum film or silver ink, it’s probably the cheap ink type. Second, look for third-party testing. We get our blocking cards tested by independent labs every six months to make sure they meet ISO 14443 standards for RFID/NFC blocking. That’s the international standard for contactless payment cards, so if a card isn’t tested to that, it might not work. Third, avoid cards that are too thin or too cheap. If you’re paying $1 for a single blocking card, it’s almost certainly using the cheapest materials possible, and it will fail when you need it most.
As someone who’s in this business, I’ve seen the good and the bad. A few years ago, a customer came to us because a set of cheap blocking cards he bought for his whole family had stopped working after a month. He’d left his wallet in the back of his car for a day in 90-degree heat, and the adhesive in the cards had melted, causing the aluminum film to shift. He asked us why our cards cost a bit more, and I showed him the lab test results, the material specs, and how we test for temperature resistance, scratch resistance, and signal blocking. He ended up buying a 10-pack for his whole family, and a year later, he emailed us to say none of them had had any issues. That’s the kind of customer story that makes this work worth it.
So, to circle back to the original question: what is a blocking card made of? It’s a carefully constructed multi-layer product, not just a hunk of plastic. It’s a rigid, durable PET base, a thin, frequency-tuned aluminum shielding layer, a strong adhesive to hold everything together, and a scratch-resistant outer laminate. The materials have to work together to block exactly the signals you need them to, without interfering with other devices, and without falling apart after a few months of use.
If you’re looking to invest in blocking cards for yourself, your family, or your business, it’s worth asking the supplier about their materials, their testing process, and the lifespan of their products. At our company, we’re always happy to walk you through that—because we know how important it is to feel secure when you carry your personal information with you every day. Whether you’re worried about someone skimming your credit card on the bus, or protecting your passport details while you travel, a good blocking card is a small, affordable investment in your privacy. If you have questions about our blocking cards, or you’re looking to place a bulk order, don’t hesitate to reach out. We’re here to help you find the right solution for your needs.
RFID LF Card References
ISO/IEC 14443: Contactless Integrated Circuit (IC) Cards, Proximity cards
Faraday, M. (1836). Experimental Researches in Electricity, Series XI
National Institute of Standards and Technology (NIST) Special Publication 800-98: Guide to Secure Radio Frequency Identification (RFID) Applications
Polyethylene Terephthalate (PET) Material Properties, Plastics Industry Association, 2022
Shenzhen Razlon Technology Co., Ltd.
Shenzhen Razlon Technology Co., Ltd. is one of the most professional blocking card manufacturers and suppliers in China, specialized in providing high quality customized service. If you’re going to buy or wholesale bulk blocking card in stock, welcome to get quotation and free sample from our factory. For price consultation, contact us.
Address: No. 5 , Lin Chun, Xisheng Street, Tangxia Town, Dongguan City China. 523711
E-mail: Rachel@razlon.com
WebSite: https://www.razloncard.com/
