Boston Marathon Bombs: What Were They Made Of?


As details start to trickle out in the aftermath of the Boston Marathon Bombing, a clearer picture is starting to emerge. While authorities still have not released any information relating to the identity of the person or group behind the attack, on Wednesday information relating to the type of bomb used in the attack was released.

The release of this information provided a somewhat clear picture to what happened on that terrible Monday in April. Investigators have reason to believe that at least one of the bombs was built utilizing a pressure cooker as the overall container for the bomb, black powder or gunpowder as the primary explosive, and ball bearings along with nails to act as shrapnel to increase the overall lethality of the device. The overall container was placed in a dark nylon bag or backpack and detonated on a timer rather then by remote control. Although this information answers part of the "how" of the bombing, it does not bring us closer knowing the identities of the bomber or bombers.

The combination of a pressure cooker and gunpowder pegs the bombing as relatively unsophisticated and inexpensive. Gunpowder explodes relatively slowly compared to military grade explosives such as C4 or TNT. The pressure cooker is utilized as a cheap way to increase the pressure in the container before it ruptures in an explosion. This increased pressure would result in a more powerful blast wave and the shrapnel flying at higher velocities. An excellent example of how pressure can increase the power of a gunpowder explosion can be seen in this video.

All of the materials utilized in the bombing suggest a relatively unsophisticated operation. The bag, pressure cooker, timer, and materials used shrapnel can easily be purchased secondhand, on-line, or in a store such as Wal-Mart. Gunpowder can be easily purchased over the Internet or in a specialty store. All of this could be assembled in a garage over a couple of weeks at most. Investigators claim that the design and components of the bombs were generic but a marking of "6L," indicating a six-liter container, could be made out on one of the fragments. This marking could assist in identifying the brand of pressure cooker utilized in the device and aid the investigation.

Photos of the suspected bomb have been released by the FBI:

The pressure cooker method is not a recent development in bomb making circles. Al-Qaeda’s Inspire magazine had instructions to build a pressure cooker bomb back in 2010. However this is not the smoking gun that it appears, as the method was apparently published in the 1971 book The Anarchist's Cookbook. And although similar devices have been utilized in Afghanistan and Iraq for improvised explosive devices, no foreign connection has yet been found. In comments to CNN, Senator Saxby Chambliss (R-Ga.) said that "There are a lot of things that are surrounding this that would give an indication that it may have been a domestic terrorist, but that just can't be assumed." Some experts are claiming experts are claiming that the relatively small scale of the attack and the crude nature of the attack points to an individual or small group rather then large established terrorist networks.

Although crude, the bombs still had a deadly effect when the detonated, injuring 183 and killing three: Chinese graduate student Lu Lingzi, 29-year-old Krystle Campbell, and 8-year-old Martin Richard. As authorities discover more information about what happened on Monday we can only hope that knowledge of what the bombs were will help them bring the perpetrator to justice.