<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bergy</div><div class="ubbcode-body">Maybe you could post a picture of the thermal image of an actual block stamp. Metallurgically, I guess that the internal stress could impact the heating/cooling rate very slightly. I don't understand why the thermal unit would pick up a stressed area in the absence of heat change though. Worth a try - show us what you have observed. </div></div>
Because there is NO WAY for a "forger" to duplicate the properties of the metal in the original mold, thermal IR will show the difference in the properties of the metal. In addition, one would have to grind the original stamping (which would also change the properties of the original metal and show up on thermal IR), then build the area back up, presumably via a weld, stamp the new numbers, and then "clean up" the entire area around the new numbers. Frankly, an exhaustive process, but one that puts a significant amount of stress on the original casting, as well as adding new material with different properties. Here is a thermal IR image of a common weld, cold (no heat applied).
If you imaged the block while hot, it would be even more pronounced but as you can see, heat is not needed to detect a weld. Believe it or not, a weld will also cause a very small amount of moisture or sweat, even though you can't see it. Here is a thermal IR image of moisture trapped in the metal.
Sometimes, you don't even need thermal IR, although, I think it's more accurate. Here's an IR scan of a "clean" weld (one that has been fully worked/blended with the original material.
