I have posted this before.
The best solution strength is not a lot, strong enough to raise the temperature of cold water to warm.
But If you mix it strong enougth for the water to be hot, the solution will boil when it finds
some aluminium to react with; it usualy blows it self out of the tubes at this strengh.
I did post some pics of taking a marin seat post out, I measured the temp of the water and even mixed a
bit to strong to see how hot was to hot.
If the seat post has been chopped off I block the open end. Then I hold the frame upside down and
pour the caustic through a bottle hole. You have to empty it out and flusgh it clean when the casutic
reaction slows down[when the frame cools down]. Then you fill with fresh caustic mix.
Does the caustic get hot and eat aluminium?
Pound shop caustic has other stuff in it and it doesn't do the job.
I sawed a post out of an aluminiun frame, pretty quick and easy.