Melt Globule
Definition
A rounded metal deposit formed when a conductor is heated to melting by ambient fire heat rather than by arcing; physically similar to an arc bead but shows a different solidification microstructure under SEM/EDS examination.
- Cause
- Ambient fire heat, not arcing
- Shape
- Rounded metal deposit on conductor
- Distinguished from
- Arc bead
- Examination method
- SEM/EDS solidification microstructure
Common questions
Why does the microstructure matter if the globule looks like an arc bead?+
Arc beads form in milliseconds from localized electrical energy and solidify with a distinct grain structure, while melt globules cool more slowly from surrounding fire heat. SEM/EDS can distinguish the two solidification patterns even when the surface shape looks similar to the naked eye.
Does finding a melt globule rule out an electrical cause of the fire?+
Not by itself. It shows that particular conductor melted from external heat rather than arcing, but other conductors at the scene may still show genuine arc beads. Each melted point needs its own microscopic examination before drawing a conclusion about origin.
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