I’ve reached an age where I spend quite a lot of time gazing into the middle distance, a wistful, glazed expression on my face, revisiting the exploits of my youth.

A lot of those exploits took place in various wooded areas near my home, and not all of them involved leafing through discarded porno mags. I bought my first “proper” mountain bike when I was twelve years old, and have stayed interested in them ever since. I was twelve in ’94, and the bike I bought was a Raleigh M-Trax 1500, complete with (absolutely useless, even by the standards of the day) Marzocchi Zokes front suspension.

In 1994, no-one had heard of hydroforming, and aluminium was still pretty much only used by high end, boutique manufacturers. Most bikes had frames made from steel. So, when I do my middle distance wistful face, I’m usually remembering steel framed bikes. Which was fine, until I started looking at them on eBay, and quickly realised I could pick up the sort of bikes I used to drool over in catalogues for buttons. Once the retro bug bites, it’s hard to stop looking.

I’ve ended up with a 1997 steel framed Voodoo Erzulie in my garage. This one actually cost me nothing, but nothing free is without a catch. In the case of this bike, the catch is that it hasn’t been at all looked after. There’s plenty wrong with it, and not a lot right, but the most annoying thing was the seatpost.

It had seized in the frame, and no amount of leverage, hammering, laborious hacksawing or swearing could persuade it to budge. The trouble with steel is that it reacts with aluminium, the material of choice for most seatposts. The two metals corrode together, forming a chemical weld which is immensely stubborn.

I can’t give up on something once I’ve started, so I consulted the bible and discovered that the last resort in these cases is to corrode the seatpost using a caustic soda solution. This appealed to me, not only because it would mean I could remove the post, but I would be removing it using actual SCIENCE. Like Walter White, but less ruthless and crazy (and clever). Yay science, bitch!

Disclaimer: Caustic soda mixed with water is quite nasty stuff. You don’t want it on your hands. You definitely don’t want it in your eyes. You don’t want it to get on anything aluminium which you would like to continue existing. Wear gloves. Wear goggles. Rinse everything with plain water afterwards (I didn’t rinse my patio well enough, and found it was growing crystals a few days later…)

This isn’t an instructional post, if you want to find out how to remove a seatpost with caustic soda you can Google it and find out easily. What most of those instructions don’t say is that caustic soda MAY damage your paint if you don’t protect it. My Voodoo now has some very yellow areas, and some paint which has cracked and is flaking away. I’ll probably be Nitromorsing the whole thing and lacquering over the raw steel at some point.

It is fun though. The reaction is immediate, and reminiscent of a well shaken can of Coke. I left it overnight, fizzing away, and in the morning, the post pulled straight out. It looked like this:

caustic soda seatpost

Probably not safe to use anymore…

The moral of the story here: if you have a steel frame, make sure you grease your seatpost every now and again.

Oh, and don’t buy old, knackered, bikes unless you enjoy taking them apart and rebuilding them. Luckily, I do.



  1. who doesn’t love a bit of semi dangerous science? Although if it does that to aluminium….

    1. Aluminium’s a pretty wussy metal though, isn’t it? Can’t be that strong, I mean who can’t crush a Coke can? 😉

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