In penetrant testing, what must be carefully managed to avoid false indications?

In penetrant testing, ambient light levels are crucial to managing false indications. This non-destructive testing method relies on the visibility of penetrants that seep into surface defects and become visible under ultraviolet or visible light. If ambient light is too bright or uncontrolled, it can obscure or wash out the fluorescent indications made by the penetrant, leading to missed defects or false readings. Properly controlling lighting conditions ensures that any indications generated by the penetrant can be accurately observed, thereby increasing the reliability of the test results.

The other options involve important aspects of the testing process but do not directly relate to managing false indications caused by external factors. For instance, while the type of penetrant used is significant for ensuring compatibility with the material being tested, it does not address how external light affects the visibility of the results. Similarly, application time of the developer and cleaning of the work area are essential for ensuring the integrity of the testing process, but again, they do not address the issue of external light impacting the detection of defects during the testing phase.