What material change would be considered a defect in rubber insulating gloves?

Ozone cutting or checking is considered a defect in rubber insulating gloves because it indicates degradation of the rubber material caused by exposure to ozone. This chemical reaction can create cracks or checks on the surface of the gloves that compromise their integrity and protective qualities. Such damage can lead to a failure of the glove to insulate properly, posing a significant safety risk in electrical work, where high voltages may be present.

In contrast, other options like loss of grip, color fading, or stitching coming undone may not directly affect the gloves' insulating properties or electrical safety. While they may indicate wear and should be monitored, they do not represent a fundamental breakdown of the glove's material that could result in hazardous conditions as ozone cutting does. Therefore, the presence of ozone cutting or checking is critical to assess to ensure that the gloves continue to provide safe and effective protection against electrical hazards.