Disclaimer time - I know that investigating the oddities of published reports puts me in the company of some real nuts and wackos. I also know that questioning or querying the official reports as they come in tends to aggravate some people, who don't even want to hear it. So be it, on both accounts.

Secondly, I have no idea who set up these bombs and I'm not saying I do. My job is to ask questions not to promulgate answers. If you think I'm pointing the finger at group X or group Y and saying "they did it" then you aren't reading what I'm writing.

Thirdly, I am fully aware the investigation is not over and I do hope that when it is completed a lot of these questions will be answered.

Furthermore, let me add something I read in a book. From Pattern Recognition pages 293-294:

There must always be room for coincidence. When there's not, you're probably well into apophenia, each thing perceived as a part of an overarching pattern of conspiracy. And while comforting yourself with the symmetry of it all, you stood all too real chance of missing the genuine threat, which was invariably less symmetrical, less perfect.

Fair enough?

This case has already taken a number of strange and odd turns. And now we have one more bit of weirdness, which is that the New York Police Department decided to hold a sort of press conference yesterday and make a number of revelations about the case:

The July 7 attackers used hair bleach and citric acid to prepare the explosives that killed 52 innocent people in London four weeks ago and set off their bombs with mobile phones, according to the New York Police Department.

Ray Kelly, the New York Police Commissioner, told a mixed audience of police and private security officials from New York's banks, hotels and storage facilities that the explosives used on July 7 were not military grade, as was originally thought, but were made of products that can be bought on any high street.

"Initially it was thought that perhaps the materials were high-end military explosives that were smuggled, but it turns out not to be the case," said Commissioner Kelly. "It’s more like these terrorists went to a hardware store or some beauty supply store."

According to NYPD investigators, some of whom flew to London within hours of the attacks on July 7, the three bombs that exploded within seconds of each other on the Underground system were probably detonated by mobile phones with their alarms set for 8.50am.

In an unusually detailed briefing, officials from the NYPD's large anti-terrorism department, said that the bombs used a peroxide-based explosive called HMTD, or hexamethylene triperoxide diamine. HMTD can be mixed from mundane ingredients such as hydrogen peroxide (hair bleach).

Right off the bat you can see how odd this is - the NYPD revealing all kinds of information in an "unusually detailed" briefing. The NYPD's website doesn't yet include a transcript of this briefing (if it ever will) so we'll have to rely on a number of different articles to learn Kelly said.

I'm going to skip over the information about the explosive for now and focus on the other details. Cell phones? That's extremely interesting because we have already determined in other parts of this series that cell/mobile phone calls are not possible in the underground sections of the London subway system.

However what Kelly seems to be referring to is using cell phones as timers rather than as remote activators of bombs. Using a cell phone as a timer is extremely simple and was how the bombs were set off in the Madrid attacks in 2004.

Many mobile phones, including an extremely common and cheap Nokia model I used to own (in Europe), have an "alarm" feature. These phones can be turned completely off and will turn themselves on at the time of the alarm (a picture of what I'm talking about here). So this is a very credible explanation from Commissioner Kelly, except for the fact that it goes completely against all the other reports which say there weren't any timing devices found.

Of course many ordinary people died on the train explosions and many of them may have had cell phones in their possession, thus mixing those components into the wreckage at the blast site. But for police to be able to link a particular cell phone with the bomb means that there is some kind of connecting evidence. The problem is that if the cell phone is connected to a bomb of any significant explosive power, it would be disintegrated into fragments.

The way the Madrid police determined that cell phones were used as timing devices in the 2004 attacks was when they discovered an unexploded bomb which had the timer set incorrectly (PM instead of AM). Police then tracked down the cell phone vendor and the fingerprints on the phone, which led to more evidence and suspects and eventually to the case being resolved.

I think Kelly in this case is extrapolating a little bit too heavily on the issue of cell phones-as-timers. I note that he said "probably used" rather than a more definitive statement.

One more paragraph from the above article:

After the briefing, Paul Browne, an NYPD spokesman, said the department had clearance from British authorities to present the information about the explosives used on July 7.

Well that all seems to imply that the NYPD asked the British before divulging all this information. So why would the British police want the NYPD to reveal new information to the public? Police departments thrive on big cases because it gives all the top brass a chance to see themselves on television. Why let the Americans steal the limelight?

Today's Washington Post has a different take on the matter:

Britain's anti-terrorist branch would not confirm the U.S reports and have previously said details about the explosives could be an important part of their probe. Officers indicated they were unhappy with the U.S. revelations.

"It's not something that we would normally want to do," Deputy Chief Constable Andy Trotter of the British Transport Police told BBC Radio. "That's a matter for them."

U.S. officials, who said the British had given them clearance to release the information, told the briefing the bombers used a volatile peroxide-based explosive called HMTD, or hexamethylene triperoxide diamine.

This can be made from simple ingredients such as hair bleach, which contains hydrogen peroxide, citric acid, and heat tablets, sometimes used by the military to cook food.

Reading between the lines here, I think that the British police were ok with the NYPD talking to other police agencies and security firms about the bombs in an effort to warn them about what to be on the lookout for. I think however that they did not want this information to be put in the newspaper.

So let's talk about this explosive, identified as hexamethylene triperoxide diamine (HMTD).

Wikipedia just describes it as an explosive often used in improvised devices made from ordinary ingredients. This is true. The various news reports list the ingredients as "bleach, citric acid and military heating tablets".

That's somewhat right. I'm going to go ahead and give a lot of specific information about HMTD because it isn't a secret. Please don't confuse frank and forthright discussions about public information as some kind of advocacy to commit terrorist attacks with explosives.

HMTD is made with three ingredients: hydrogen peroxide, citric acid and a chemical known as hexamethylenetetramine.

The hydrogen peroxide can be found in a number of ordinary products but the simplest way to obtain it is bleach used for changing the color of your hair. Ordinary hair bleach contains between 3 and 6% hydrogen peroxide but you can get it in more concentrated forms from beauty supply stores. HMTD however can be made just fine from the lower percentage product.

The second ingredient is citric acid, which is sold in jars and is a white powder. It's usually sold as a food additive and you can get it from some drug stores and health food stores in the United States.

The third ingredient is the hexamethylenetetramine. There are two ways to get this, one is to buy "solid fuel" products, often used by campers or the military, similar to (but not the same as) Sterno. They are often sold under the brand name Esbit or are referred to as "Hexamine Fuel Tablets". I have no idea about the availability of the commercial forms of these products.

Hexamethylenetetramine can be quite easily synthesized however from formaldehyde and ammonia. In fact, all you do is mix the two liquids (in the right concentration) and let them evaporate and the resulting powder is hexamethylemetetramine.

The process of combining these three ingredients is extraordinarily simple and the only equipment necessary is a couple of glass containers and some ice. A heat source is not even necessary. The liquids are mixed and left to evaporate and the resulting precipitate (powder) is HMTD. I should add here that HMDT looks very similar to crack cocaine.

HMTD, because it is so easy to make, has often been used in amateur pyrotechnics and people curious about making small explosions/exploding devices. Therefore its properties and manufacture are well known. I appreciate the NYPD's informative lecture to police agencies and security firms but really this is something they should all be well aware of already.

Back to the Times article:

The only unusual piece of equipment the bomb-maker needed to produce large quantities of HMTD was a commercial refridgerator, because the explosive degrades if it is left at room temperature.

Yesterday, NYPD officials said that an expensive fridge was found in the otherwise rundown flat in Dewsbury, on the outskirts of Leeds, where investigators believe the bombs used on July 7 were built, and that the devices were brought to Luton in cooler boxes in the boots of two cars.

"In the flophouse where this was built in Leeds, they had commercial grade refrigerators to keep the materials cool," said Michael Sheehan, the NYPD's Deputy Commissioner of Counter Terrorism.

Mr Sheehan told the conference that the presence of sophisticated cooling equipment in an unlikely place could be "an indicator of a problem".

Actually HMTD doesn't begin to seriously degrade until it reaches temperatures of 70C/158F. It does degrade over time but if stored in proper receptacles, it has a "shelf life" of at least two years. I'm not sure what a "commercial grade" refrigerator is versus an ordinary one, but clearly even "room temperature" in England would never approach anything like 70C/158F.

If indeed these materials were found in a commercial refrigerator the likely explanation is that someone had an old commercial refrigerator and used it simply because it was free. I should add here that HMTD will begin to degrade at "room temperature" but not excessively.

The most important element of storing HMTD is the material in which it is stored (or packed) because it is highly reactive to most metals. There is no "safe" metal to store or place HMTD in because it will rapidly corrode copper, brass, iron, lead or steel. This however can be circumvented by coating the metal with a non-reactive substance such as varnish or cardboard or even grease paper (baking paper). Or it can be stored in plastic, which corresponds to the other reports that 6.25 liter "tupperware" containers were used.

HMTD can be detoned/ignited in two ways - one is a severe shock such as a direct blow or strike or by being ignited. This makes it sensitive to shock, in its pure form. It can be mixed with other substances to provide more stability and I'll discuss that below.

The problem with the 7/7 bombers using HMTD is that it is a "primary" explosive. Most chemical explosives are composed of two elements - a primary explosive and a secondary explosive. The "secondary" explosive is usually much more powerful but more difficult to detonate. Therefore the "primary" explosive, which is less powerful but easier to detonate, is detonated which then detonates the secondary explosive.

HMTD is definitely an explosive but it falls into the first category, a "primary" explosive. A "blasting cap" is the term of a primary explosive which is ignited/detonated to set off the larger and more powerful explosion. Amateurs have been making blasting caps with HMTD for quite a while because of its ease in ignition.

Primary explosives, if in powder form, are often "tamped" or pressed into a receptacle to increase their efficiency and explosive powder. This however is extremely dangerous with HMTD due its sensitivity to shock.

Therefore HMTD, if in its loose and untamped form, is not an extremely powerful explosive. I don't have access to technical data to know how much HMTD it would take to get the explosions that happened on 7/7 therefore it's impossible for me to guess if this was the only explosive the bombers used.

An ordinary cigarette lighter or the equivalent will not cause HMTD to explode - instead it will just burn very brightly and hot. Aside from a strong shock or percussion, the best way to detonate HMTD is by a fuze. There are igniters which can be purchased in craft/hobby stores for model rockets but in the case of HMTD they would be ineffective.

Fuzes can be handmade in a number of different ways which are then ignited by a very low-level electrical charge, certainly less than what a cell/mobile phone has. These fuzes however require some kind of igniter material to detonate the HMTD, in this case making the HMTD the "secondary" explosive in the device.

I should mention here that the military uses electrical igniters called "squibs" which may or may not have been available to whomever manufactured the 7/7 bombs.

Now as I said earlier, HMTD can be stabilized by mixing it with other chemicals to convert it into a plastic explosive. A "plastic explosive" is a term that simply means an explosive that's combined with a stabilizing ingredient. While the stabilizing ingredient helps improve the "shelf life" and would make it much safer to pack/tamp HMTD, it also reduces its effectiveness.

According to the ABC photograph of the bombs left in Luton, the bombs were plastic containers filled with a white substance. This certainly would make sense if they were HMTD. However the bombs also contained nails and screws which would very rapidly corrode in the device and possibly degrade the explosive power of the bomb.

A terrorist seeking to set off more powerful bombs could use HMTD as a primary explosive and other more powerful materials as the secondary, such as RDX. I should mention here that RDX can also be made at home with fairly ordinary ingredients although it does take a little more effort. HMTD is roughly half as powerful as TNT while RDX is roughly 1.2 times more powerful.

Of course I'm not a terrorist and don't know whomever made these bombs so it could be that they just decided to use HMTD because of its simplicity in both manufacture as well as the ease in which the ingredients necessary could be procured.

One more thing to take into consideration is that previous parts of this series a witness reported that a bomb in one train appeared to come from underneath the carriage, exploding upwards. In the case of HMTD being exploded by a percussive force, this is technically possible if the train ran over the device. However this would have to have occurred when the first carriage struck the device and the explosion would've hit the front of the train, i.e. the driver's compartment.

Now here is an ominous addendum to the NYPD's revelations:

The bombers who botched similar attacks on London on July 21 had similar devices, but their detonators were hand-activated not timed, the U.S. officials revealed.

I'm not quite sure what they mean by "hand activated" but certainly if the bombs were manufactured by the same person(s), that ties the two events together. Up until now, the evidence seemed to be that the 7/7 bombings were extremely sophisticated while the 7/21 bombings were nearly akin to a kind of "prank" by an unrelated group.

Since the 7/21 bombs failed to explode, it could be that they had indeed degraded into a non-explosive compound (which HMTD will do) just two weeks after the 7/7 bombings. If they had been stored in a hot garage in London this is definitely a real possibility.

However I do note that Muslim men (in this case Bangladeshi) have been found with HMTD in Britain in the past - specifically the case against Faisal Mostafa and Moinul Abedin in 2000 (Birmingham). The men had "stockpiled" HMDT but never used it. The apparent choice of detonators, at least what was found in the police raid of their house, was an ordinary 9 volt battery.

Mostafa also had a "50 page document" on how to make the explosives from ordinary items. Of course as I said earlier, this information is widely available on the internet as well. Mostafa was later acquitted of all charges.

So the question remains - who made these bombs? If it wasn't one of the eight bombers (all either dead or arrested), this means that the bomb maker is still on the loose.

What's also extremely ominous about the 7/7 bombings versus the 7/21 ones is that if the 7/21 bombs were designed to be "hand activated", that would make them de facto suicide bombs. However why use a cell phone timer on 7/7 if they were designed to be suicide bombs? If Kelly is right, that strongly reinforces the theory that the 7/7 bombers were not intending to kill themselves!

The investigation continues...

Peace