fixing dented headers

[vinnY]

http://www.thumpertalk.com/forum/showthread.php?t=523620
it appears freezing water in dented headers can pop out the dents, anyone happen to know why this happens?
if they totally filled the header with water i'd understand but in the article it states:

Added enough water to fill the dented area of the pipe, plus a bit more (did not end cap the pipe or plug anything).
which sort of boggles me as to how it'd make the dent pop out if it(the water) has space to expand into

anyone know any other methods of getting dents and dings out?

looking to fix my tri-y's from all the battle scars :(

[hoonda]

Doesnt make sense to me..

[vinnY]

well apparently the water in direct contact with air(each ends of the tubes) freeze first thus making sort of a 'cap' while the water in the dent slowly freezes and expands within the confined space between the 'ice caps' thus popping the dent out
thats one theory anyway

anyone else have any idea on how this may work?

edit; well it seems to make sense since water doesn't all freeze at the same rate, usually outside then in

[Kiz_EG6]

heat it up with an oxy, then jam a metal rod into the dens (from the inside :p)

[aimre]

dry ice. might help like car dents..

Depends on how big they r

[EKVTIR-T]

Someone try the freezer trick.Post results plz..
Need a big freezer though lol