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In this picture from a different question I noticed some kind of colored substance across many of the fittings. It is in several different colors and looks like it might be sticky. (The pink kinda looks like chewing gum. That's even worse than the duct tape question. ;) I have circled some of them in yellow.

Is it there to mark whether the fittings have been tampered with?

  • $\begingroup$ Typically, each mechanic will have their own color of torque seal (it comes in a whole rainbow of colors). In that way, not only can you tell if a fitting has been tampered with, but who it was who last worked on that system. $\endgroup$
    – DFurey
    Apr 8, 2018 at 10:53

1 Answer 1


That is called "torque seal" or "torque putty".

It is used by mechanics to mark a part after it has been properly torqued, and thereafter to serve as an indication if loosening has taken place. The torque seal hardens after application and serves as a marking mechanism that will show—by cracking and/or flaking of the putty—if the part has loosened resulting in rotation.

The photo below shows torque seal as initially applied (left), and then with the seal broken following loosening an rotation of the nut (right).
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Image courtesy of theleanwarehouse

Just to be clear, the torque seal does nothing to secure the part or otherwise serve any locking function. It serves only as an indication.

Dykem is one manufacturer of torque seal.

Here is a page with additional information about torque seal from a retailer.

  • 3
    $\begingroup$ And if you run out you can just use juicyfruit :) $\endgroup$
    – TomMcW
    Feb 4, 2017 at 5:50

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