What is a common challenge when detecting shallow scratch-like discontinuities?

The challenge of detecting shallow scratch-like discontinuities in materials often revolves around the emulsification process. Emulsification time is critical because it impacts the interaction between the penetrant and the surface of the material. If the emulsification time is insufficient, it can lead to improper retention of the penetrant in the flaw, making it difficult to identify the discontinuity effectively.

For shallow scratches, the penetrant must adequately seep into the discontinuity before being emulsified and washed away. If this step is rushed or not carefully monitored, the detection of these subtle flaws can be compromised, leading to potential oversight of critical defects. Thus, ensuring adequate emulsification time is vital for accurate and reliable detection in non-destructive testing methods.