1. A method comprising: heating a ground steel part that has been chemical-etched; and detecting defects caused by grinding and watermarks caused by chemical etching by imaging the steel part with an infrared camera to capture infrared radiation from regions of the steel part that include defects and watermarks, wherein imaging the steel part comprises: imaging regions of the steel part at long-wavelengths of infrared radiation to detect defects on the regions of the steel part; and generating a first image wherein the defects are visible in the image and the watermarks are not visible in the image.