The Alcohol Wipe Test as a Non‑Destructive Inspection Technique

The alcohol wipe test (AWT) is a simple, low‑cost inspection method that has been used as a qualitative, non‑destructive screening technique to reveal surface‑breaking and near‑surface discontinuities. By applying a volatile solvent—most commonly isopropyl alcohol—to coated or bonded surfaces, the test leverages differences in evaporation behavior, capillary action, and surface energy to produce transient visual indications such as darkening, bubbling, or delayed drying. These indications may correlate with cracks, coating defects, disbonds, or localized contamination.

This presentation examines the physical mechanisms underlying the alcohol wipe test and evaluates its effectiveness within the broader context of nondestructive evaluation (NDE). Factors influencing detectability—including surface condition, coating integrity, environmental conditions, and defect morphology—are discussed through representative case examples. The limitations of the method including environmental effects, inspector subjectivity, and the potential for false negatives, are emphasized.