Which action is likely to decrease the sensitivity of liquid penetrant examination?

Reprocessing a previously examined specimen is indeed likely to decrease the sensitivity of liquid penetrant examination. This is because the initial examination may have already removed or altered the penetrant within any defects or discontinuities that were present. When a specimen is reprocessed, the previous penetrant pooling within cracks may be diminished or lost, leading to potential false negatives where defects are not indicated adequately.

Additionally, using a fresh penetrant typically increases sensitivity, as it ensures that the penetrant is effective and capable of drawing into any defects. Adjusting the inspection light can enhance visibility but does not inherently affect the sensitivity of the penetrant itself. Cleaning the surface before examination is crucial for ensuring that no debris or contamination interferes with the penetrant's ability to settle into cracks, thus maintaining or enhancing sensitivity rather than decreasing it.