Wednesday, February 02, 2011

Boom Bang A Bang

I don't know. When the 7/7 bombers struck, the press was full of stories to the effect that

a) the bombs were home-made TATP explosive, as used in home-made Hamas rockets.
b) there was a fully-equipped cookshop in Hyde Park, Leeds, where the TATP was brewed.
c) said cookshop belonged to an Egyptian chemist who happened to have gone to Egypt. The chemist was named as Magdi Mahmoud al-Nashar, of Leeds University. Apparently he was detained in Cairo by Egyptian police and interviewed by a couple of Special Branch officers - after which it was quietly announced that no charges would be brought. He doesn't seem to be at Leeds any more.

Then we were told 'organic-peroxide' bombs. I assumed flour and peroxide as that seemed to be the choice of the 21/7 bombers. In fact the 21/7 wiki, for what that's worth, said "The explosives used by the bombers consisted of Chapatti flour powder mixed with liquid hydrogen peroxide, detonated by a booster charge. This was the same explosive mixture used by the bombers in the 7/7 bombings two weeks earlier."

Yet the 7/7 inquests are now apparently telling us the bombs were peroxide and black pepper. Sounds like a flavour of crisp.

"The bombs used in the attacks on three tube trains and a double-decker bus contained about 10kg of explosives made from a mixture of concentrated hydrogen peroxide and pepper and detonated by a 9-volt battery. Forensic explosives expert Clifford Todd said using this combination of materials for a bomb was thought to be "entirely unique" both in the UK and worldwide."

The Telegraph has most detail :

"The July 7 bombs and July 21 bombs were not identical, but they were, a source at DSTL said, "similar in principle". Both were a mixture of hydrogen peroxide, made by boiling down hair products, and an organic material - in the first case black pepper, in the second chapatti flour. The detonators were also similar - in the case of July 7, made from hexamethylene triperoxide diamine (HMTD), made by combining hydrogen peroxide, hexamine tablets from camping stoves, and an acid such as citric acid or dilute sulphuric acid. In the case of July 21 the detonator was triacetone triperoxide (TATP), made by combining hydrogen peroxide, acetone from nail varnish and sulphuric acid. The differences amount to just two main ingredients - nail varnish rather than camping stove tablets and flour rather than pepper - and leave the possibility that both bomb-makers were taught by the same man. The cost of the devices was also relatively low - just £500 was spent on hydrogen peroxide."

It must be a pain boiling down all that hairdresser grade peroxide (17 vol?) when a chemical supplier can do you 100 vol.

Now call me daft, but why pepper ? Indeed, why flour ?

I guess you want something flammable (high heat of combustion per gram), fine particles, can be soaked in concentrated peroxide. I've forgotten my chemistry - wouldn't charcoal be better, or doesn't it burn fast enough - as I guess the speed at which the mixture burns affects the power of the bang?

I suppose the driver is that the fuel must be able to mix intimately with the H2O2 - which is a watery oxidiser. Can't mix that with, say, diesel, as oil and water proverbially don't mix.

Is there someone in the Kurram Valley or Mohmand grinding up various foodstuffs and evaluating them as explosives? Seems that there must be.


Cee said...

I'm currently looking up information on how quickly charcoal dust burns, but the idea behind using organic powders (like flour and pepper) is that when mixed with an oxidizer or just air, they burn fast and hot.

I imagine powdered charcoal would work as well, but the slurry produced by the mix of hydrogen peroxide and charcoal powder would be less tractable to work with than hydrogen peroxide and flour. Additionally, if you're the sort to suspect your purchases are being monitored, a purchase of hydrogen peroxide and chapatti flour looks much less suspect than hydrogen peroxide and a bag of charcoal. In a "oh, they're getting some supplies for a first aid kit and the kitchen" versus a "they're purchasing supplies FOR A BOMB" sense.

Cee said...

Or, in this case, they're getting a bunch of nail-polish remover and flour. Much less traceable that way.

Anonymous said...

Flour and pepper are explosive in their own right due to the high surface area for burning, so as Cee says if you just ignite them in air they will explode. Put them in the presence of a strong oxidiser like Hydrogen Peroxide and its more or less job done I would say.

Anonymous said...

Have you seen 7/7 Ripple Effect yet Laban?

JuliaM said...

"Yet the 7/7 inquests are now apparently telling us the bombs were peroxide and black pepper. Sounds like a flavour of crisp."

*hopes for another Walkers competition to create a crisp flavour*

Anonymous said...

Such drolleries!

Just on a point of logic little Englander - and I share your general nausea. You said we should not give a shit about foreigners but go all Bismarkian or Metterelinkin or whoever it was. But you pointed out that we are 'tied to' the USA and they were 'tied to' (nice phrase) Israel. So we're apparently stuck with it. Such a power this small contry in the middle east has to have us all in thrall. Darfurians don't get a look in - the ones who are still alive. What have they actually done for us except kill our troops and blow up hotels? Have you forgotton? No, I dont hate Jews or Yanks so shut the fuck up you feel like starting. If Israel were over-run I would not be celebrating. I'm not driven by hate.

Laban said...

Are you sure you're on the right thread? Even the shiniest of tinfoil hats hasn't AFAIK linked Israel to 7/7.