Duration: 0:48

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A short video showing the caustic soda at work. It is dissolving the aluminium seatpost that has become stuck in a steel frame. The frame is an early 90's GT Bravado.

I sealed the hole to the bb at bottom of the seat tube. Then I taped a plastic bottle to the top of the seat tube and cut off the bottom of the bottle. This to prevent or limit overflow as the caustic soda started to react. I then added water to the seat tube and finally added quite a lot of caustic soda, 100-200 grams initially, and maybe more later if needed.

This will only work on an aluminium seatpost stuck in a steel frame. Caustic soda dissolves aluminium, but not steel. Do not do this to an aluminium frame. You will ruin your frame.