Use a Wax Crayon, Not Penetrating Oil, on a Heated Stuck Bolt
The Problem
Heat is the standard escalation for a rust-seized bolt: expand the joint, break the corrosion's grip. The instinct is to follow the heat with penetrating oil — but sprayed onto hot metal, penetrant mostly evaporates before it reaches the threads, and it can flash into flame. You lose the lubricant exactly when the joint is most ready to accept it.
The Technique
- Heat the seized fastener with a torch.
- Touch a wax crayon to the joint where the threads meet the surrounding metal.
- The wax melts on contact and capillary action draws it down into the threads as the metal cools — it stays put and keeps lubricating instead of boiling off.
- Work the fastener loose.
Side by side on hot metal, penetrant visibly evaporates while the wax flows in and stays — that difference is the whole method.
Pro tip: Any plain wax works — a candle or a chunk of paraffin does the same job as a crayon. The crayon is popular because it's cheap, fits in a toolbox, and the paper wrapper keeps your fingers off hot metal.
Safety note: This is open-flame work. Clear flammables from the area, know what's on the other side of the panel — fuel lines, brake lines, wiring — before heating, and keep an extinguisher within reach. Never spray penetrating oil at a torch-hot part; most penetrants are flammable.