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Comment by krenoten | Hacker News Reader

It's part of a hardening process that has been employed by weapon smiths for time immemorial, known as "quenching". After you form the laptop case / sword / rifle barrel, and it is still hot, it is to be submerged in urine. I'm surprised it's taken laptop manufacturers so long to catch up.

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In the UK there's a TV show called QI ("Quite Interesting"), hosted by Stephen Fry, which likes to dig up "quite interesting" odd "facts" (in quotes, as sometimes they are twisting things quite far) and ask questions about them. Especially things that will get the celebrity panelists to give "obvious" but wrong answers (which they are penalized for).

One of their questions years back was "why does the House of Lords smell like wee?"

Supposedly it at least used to because stale human urine used to be used in the manufacture of Harris Tweed, which used to be the favoured cloth for suits worn by the peers. Which was not usually a problem, except, supposedly, when it rains, at which point the suit would smell faintly of urine. Gather a few hundred of them together in a room...

Here's a thread from the QI forum regarding the topic - the whole thread is quite amusing, but the end contains a fuller description, with their sources:

http://old.qi.com/talk/viewtopic.php?t=1694&start=0&sid=5efc...

> but the end contains a fuller description

That's a _terrible_ pun: http://en.wikipedia.org/wiki/Fulling#Scouring

Supposedly BMW did that to their turbo F1 engines in the eighties. They would have a bunch of blocks sitting out in the cold, and they would pee on them to age them. That and welding the cylinder head to the block gave them 1500 hp out of a 1.5 liter engine for one lap.

http://www.autoevolution.com/news/turbocharged-engines-in-fo...

Wow, I honestly thought you guys were both trolling. From the article above comes this brilliant hack:

  While some may laugh at this strange solution by the German manufacturer,
  the urinating process is based on nitridization (a process which introduces
  nitrogen into the surface of a material and is widely used in automotive,
  mechanical and aeronautical engineering, having the property of a 
  case hardening treatment of predominantly steel but also for titanium,
  aluminium and molybdenum). Why are we talking about nitridization?
  Because urine seems to contain numerous waste compounds, many rich in 
  nitrogen. We can't yet figure out how the German engineers found this 
  particular method to strengthen the cylinder blocks – and not use a 
  more technological measure – but it makes for some interesting stories to
  tell out grandsons.

That season Brabham-BMW finished first.

> having the property of a case hardening treatment of predominantly steel but also for titanium, aluminium and molybdenum).

Does that mean applying piss on your iPhone's aluminium body would harden it?

Absolutely, give it a go. It works for all Apple products. It works best in an Apple store...

Hah! I have some friends who had some beautiful (copper?) gutter pipes installed at their house. The metal had a wonderful worn look to them. When I asked how they got it that way she replied that her partner had peed all over them for some time. I've never heard of it before but it seems true.

You are totally right sir !

In the history of quenching [PDF here http://bit.ly/1ad9Akv] the author states it was common to urine for quenching.

This property seems to have independently been discovered by chinese and europeans.

I thought quenching was done with water...

Water should only be used in extreme situations where no horses, humans, or cats can be coaxed into a milking. Urine has well known properties which it lends to the steel.

Well known properties like smell?

For really special stuff, blood of a virgin, during a full moon. Bonus points if it's an equinox, or your country's Maximum Leader's birthday.

It depends on the material. High carbon steel is usually quenched in oil or air. Water quenching may cause it to shatter. Medium carbon steel can be quenched in oil , water, or impure water(typically brine). What you quench with will determine the hardness(and brittleness) of the steel, oil being the softest and brine being the hardest.

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