What is another effective method to detect hydrogen blisters?

Holding a flashlight parallel to the shell is an effective method for detecting hydrogen blisters because it takes advantage of the light's ability to highlight surface irregularities. Hydrogen blisters are surface defects that can create bubbles or blisters on the material, and when light is shone at specific angles, it enhances shadows and reflections that may reveal these imperfections. This method is particularly useful during visual inspections, as it allows inspectors to easily observe subtle changes in the surface that indicate the presence of flaws.

While ultrasonic waves, magnetic testing, and thermal imaging are all important non-destructive testing techniques, they do not specifically target the visual identification of surface defects like blisters in the same straightforward manner as using a flashlight. Ultrasonic testing primarily evaluates material thickness and internal defects, magnetic testing assesses ferromagnetic materials' surface and near-surface flaws, and thermal imaging detects variations in temperature that may indicate issues but doesn’t directly reveal surface blisters effectively. Thus, using a flashlight is a practical and straightforward method for visual detection of hydrogen blisters.