What is the usual consequence of not cleaning the surface of a specimen after penetrant testing?

In penetrant testing, which is a method used to detect surface defects in non-porous materials, proper surface preparation is critical to obtaining accurate results. If the surface of the specimen is not cleaned adequately before the application of the penetrant, residues such as grease, dirt, or other contaminants can interfere with the test.

When the surface is dirty, these contaminants can create false indications—meaning the penetrant may be trapped in these residues, leading to the incorrect interpretation of defects or the appearance of indications that do not represent actual flaws in the material. Therefore, ensuring a clean surface prior to testing is essential to achieving reliable readings and accurately identifying any real defects in the material. This is why the usual consequence of inadequate cleaning is the potential for false indications, making this option the correct choice.