Applying Materials Science to the Forensic Analysis of Candles

Generally, when a consumer product catches on fire, there is immediate cause for concern. Candles are unique in that they are consumer products intended to be repeatedly set on fire. While candles have existed in some form for thousands of years, their design, manufacture, and performance are neither simple nor intuitive. Misunderstandings regarding the behavior and performance of candles can lead to unsubstantiated claims after a candle fire causes damage or injury. This presents an interesting set of challenges when the need arises to forensically analyze a candle. Candles can “cover their tracks” as they consume wax, but specific physical evidence is also left behind that can point investigators toward a determination of cause.

In this presentation, a general explanation of candle usage, performance, and failure modes will be provided, including a discussion of “flashovers” a specific condition where the entire top surface of the wax catches on fire. Then, forensic techniques commonly applied within a failure analysis investigation will be described in the context of a 3-wick candle flashover incident investigation conducted by S‑E‑A in 2024. By applying materials failure analysis tools and techniques, including fractography, light microscopy, FTIR, TGA, DSC, open-cup flash point testing, and a practical burn test culminating in a lab-induced flashover, the cause of the incident was able to be determined.