An age-old challenge for thermographers is the ability to annotate or mark objects to make them easier to identify in recorded imagery. One possible solution is to mark targets with an ink pen with low emittance ink.
Many thermographers have long sought ways to mark targets in such a fashion that numbers or text can clearly be seen with a thermal imager. Over time, some thermographers have used paints with emittances that contrast sharply with the objects being marked. In these cases, text and/or numbers painted on the target are clearly visible within resulting thermal imagery and recorded thermograms.
Recently some thermographers have reported good results in utilizing a Sharpie permanent felt-tip marker in silver color. The low emittance of the metallic ink contrasts markedly with high emittance targets allowing annotations to clearly appear within thermal images. In many cases, the silver ink can also be clearly seen in daylight images as well. An example can be seen below.
One should be aware that Sharpie markers are permanent unless the ink is applied to a removable material such as tape or labels affixed to the target. Prior to marking any target, be certain it is safe to do so and that marking will not permanently damage the target.
For more information on thermographer training and certification or to obtain a copy of the Guideline for Infrared Inspections of Electrical and Mechanical Systems, call Infraspection Institute at 609-239-4788 or visit us online at wwww.infraspection.com.
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