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Ink tag removal: removing ink/security tags inadvertently left on clothing and other merchandise
2003-11-16

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At some point every consumer discovers that a security device has mistakenly been left on his clothes or other new purchases by an inattentive checkout clerk.  This happened to me recently at the local Mervyn's so I took the opportunity to dismantle the device and publish this page; while I could simply have returned to the store to have the device removed (always a hassle), I admit I was curious to find out once and for all if the devices really work.  And to do it without ruining my brand new Levi's!

The Problem

The common "loss prevention" device usually attached to high-price items like leather jackets.  Apparently, Mervyn's management thinks $29.99 is a high enough price to justify using the tags.

The Solution

The cheap plastic housing of the device is no match for power tools.  Dremel multipro shown, costs approximately $30.

The Process
1.  Preliminary Observations
The device is white plastic and appears to have two halves; one half on the outside of the garment has a warning to the prospective shoplifter not to tamper with the device or risk releasing ink and broken glass.  The other half is a large cone shaped part that presumably prevents the user from tampering with the mechanism without breaking the ink packets.  Shaking the device produces a rattling sound.  It is not possible to determine which half the rattling sound is coming from.  I think the rattling is from the ink packets, but I have no idea what the ink packet looks like.  I think the ink is on the part with the warning sticker, so I'll explore the anti-tamper half first.

2.  Primary Incision

I started with a drill tip to find out what was inside the cone-shaped part.  The hole revealed some kind of plastic sheath.

3.  Exploratory Surgery

I opened up the top of the cone with the Dremel cutting wheel attachment.  When I saw sparks I stopped immediately, and observed a metal cap with a pin protruding from it.  I still didn't know what to make of this part.

4.  Empty Space & A Surprise!

I removed some more material from the top and discovered that the locking mechanism consists of a notched pin secured by ball bearings that use spring tension and metal shims to prevent the shaft from moving.  I think the removal tool the clerks have is designed to apply force directly in line with the pin; the ball bearings only prevent the pin from moving if there is force in any direction other than vertical.  A fairly elegant solution, actually.  See the diagram in section 7.
Having figured out the locking mechanism, I decided to cut into the large part of the cone to find if anything was in what I presumed to be empty space.  I was surprised to find a copper coil of wire inside––an antenna, which I assumed was designed to trigger the detector gates at the exits.  I was surprised because when I left the store the gates must not have detected this unit or the unit was defective.

5.  Mission Accomplished

I removed the top metal shim and spring, shook out the ball bearings, and the tag immediately came apart.  The half with the warning sticker did indeed contain the ink.  The ink is in small glass tubes that rest on the surface of the garment.  Presumably the pin is in fact a tack whose base is in the plastic housing of that half.  With enough force in any direction except vertical, the base of the tack would fracture the glass vials and spill ink onto the garment.
Satisfied that the cone-shaped half did not contain the ink, I opened up more of the cone and removed the copper coil.  The diagram in section 7 is a cross section of the device as assembled.

6.  Testing the Ink

The ink appears to be semi-permanent.  It has an odd chemical smell to it.  I suspect it also has permanent UV dye to prevent the shoplifter from simply laundering the clothes after staining them.  The most questionable part of the design is that the glass breaks into small slivers which could easily stick the wearer.  If this had happened to me I would have sued the store.

7.  Internal diagram

The simplest way to disable the device is to slice off the top of the cone with a Dremel or a fine sawblade, remove the top spring and shim, then shake out the ball bearings.  After that the halves come apart easily.  Now that I know how it works, next time this happens it should take me only a few minutes.

Conclusion
The ink tag has been well-designed.  It uses an innovative and cheap locking mechanism.  Like most deterrents, an ink tag can be defeated by a determined user with ordinary tools provided that the user is gentle with the device.  The device in this case malfunctioned by not setting off the reader gate at the exit after purchase.  A search for the manufacturer revealed that the device has either been discontinued or the manufacturer is no longer in business, which makes its failure unsurprising.
It would be difficult to disable the device in a store without anyone noticing.  The device has been designed to defeat attempts with scissors, pliers, and wire cutters.  It would be difficult to cut the garment under the tag because there is no space to use a cutting tool.
The ink in the device appears to be permanent or perhaps removable with a chemical solution––so the retailer can restock ink-stained items left in dressing rooms or recovered from shoplifters rather than throwing them away.
I enjoyed the challenge of this project and the "Eureka" moment was satisfying.