Gunpowder, treason and plot

November 2005 saw the 400th anniversary of the gunpowder plot. Each year we celebrate the fact that the plot was foiled but it now seems unlikely that the gunpowder would have ignited, as Katharine Sanderson finds out

The gunpowder plot. A brazen attempt to blow up the Houses of Parliament in a spectacular explosion. Thirty-six barrels of gunpowder in a cellar under the House of Lords and Guy Fawkes poised, ready to light the fuse that would blow up the King of England and Scotland and all of the country’s political elite. 

Or so the story goes. This month is the 400th anniversary of the explosive plot. But what if, aside from all the conjecture about Fawkes’ reasons for being there - whether he was a scapegoat for the rest of the Roman Catholic plotters, and how details of the plot were leaked - there is a more fundamental question to ponder. Consider the chemistry of the gunpowder. It is possible that the hoard that Fawkes and his gang stashed wouldn’t have been able to wreak the intended devastation after all.  

Rooms for rent 

It is worth looking at the security in Westminster in 1605. One of the most surprising aspects of the gunpowder plot, which flies in the face of modern day security, is that the plotters were able to rent a cellar directly beneath the House of Lords. Here they stored the barrels of gunpowder, intending to blow England’s Protestant parliament sky high. 

Unbelievable as it might seem, renting space in Westminster was normal practice for the day. As Paul Hunneyball, senior research fellow on the history of parliament project, explains, Westminster in 1605 comprised a complex of buildings that was much more diverse than it is today. It was a mixture of government and privately owned buildings, many of which were available for rent. ’People were wandering in and out of Westminster all the time on legal business,’ says Hunneyball.  

But to be able to store such a large amount of gunpowder without arousing suspicion is still surprising. ’They seem to have got away with it completely,’ says Hunneyball, ’people just weren’t very careful about security.’ 

There has been a royal bodyguard, the serjeant at arms, at the House of Commons since 1415. Muir Morton, current deputy serjeant at arms at the House of Commons describes Westminster Hall in 1605 as very much a public place. ’People had shops in there and it was a sort of thoroughfare. The possibility of getting rented rooms and getting gunpowder below wouldn’t have been too hard in those days.’ 

The location of the rented rooms was key to the plot. The state opening of parliament, scheduled for 5 November 1605, would ensure that the 27m-long room would have been crowded with its 80 members, plus all of the important MPs and, of course, King James I. 

Fawkes, who was discovered with the gunpowder in the cellar, was a Roman Catholic and had served as a mercenary for the Spanish government. He had also spent time in the Netherlands, where he learned about gunpowder and munitions. Rather than being burned as a traitor, Fawkes was hung, drawn and quartered. 

Gunpowder chemistry 

Gunpowder, or black powder, is a simple explosive. It comprises a white powder, a yellow powder and a black powder. The recipe is: 75 parts potassium nitrate (the white powder), 15 parts sulfur (the yellow powder) and 10 parts charcoal (the black powder). When gunpowder burns, these ingredients release carbon dioxide and nitrogen as gas and potassium carbonate, a solid seen as smoke. 

Black powder is explosive because air travels both within the grains of the powder, causing a chemical reaction, and in the gaps between the grains, helping to accelerate the burning.  

Tom Smith, from Davas, a UK company specialising in explosive safety management, points out the problems with getting black powder to explode. ’If the black powder wasn’t very well made, its whole burning rate would be reduced. And if it were damp or if there were impurities, that would also reduce the burning rate.’  

When black powder gets damp it leaches out its oxidation source - potassium nitrate, or saltpetre. Finding a decent source of saltpetre is another major problem in preparing good quality black powder, according to Smith. The plotters’ gunpowder has not been traced to a single reliable source, and so its quality is unknown. It had been stockpiled to the south of the river Thames and moved to the cellar over a period of several months, through a tunnel dug by the plotters.  

It is highly likely that the gunpowder would have become damp. Smith says that even if very slightly damp, gunpowder consolidates and the chance of rapid burning - enough to cause an explosion - is limited. ’It wouldn’t have the chance to burn through the open structure of the black powder as well as burning through the grains,’ he says.   

For the same reasons, gunpowder burns less efficiently if it is compacted. In the 1605 plot, the gunpowder was stored in barrels for months, and hidden under a huge pile of wood. It was almost certainly compacted to some degree. 

The evidence seems to lead to the conclusion that the plotters would not have succeeded, and that the government and the Church of England would have remained intact. 

Changing times 

Could the plot be carried out again today? Many things have moved on. Explosives have developed but security in Westminster has tightened considerably since the public thoroughfare of the 1600s.  

Not much changed in the immediate aftermath of the gunpowder plot. Hunneyball describes the collection of buildings that made up the House of Commons as ’ramshackle’ and difficult to police. He adds that ’the plot seemed to preclude anything happening again. There was a sense of revulsion’. The plot didn’t receive the sympathy the plotters had anticipated from the Catholic community. The immediate response from government was not to tighten security but to put plans in place to stamp out Catholicism in England. 

Morton, in the serjeant at arms office, describes security at Westminster, even well into the 20th century, as ’relatively relaxed’. In 1974, an IRA bomb exploded in Westminster Hall, injuring 11 people and causing a fierce fire. The only other major incident involving explosives was in 1979 when Airey Neave, secretary of state for Northern Ireland, was killed by a car bomb in New Palace Yard. 

The greatest security changes have been seen since the terrorist attacks in the US on 11 September 2001. ’If you go into New Palace Yard, which is the main area, through the big gates, there are overtly rising barriers and bollards, so nobody can drive a vehicle in there without being checked. And that principle applies at our other entrances,’ says Morton.  

Any visitor to the House of Commons today will have to go through what feels like an airport security regime, with full bag screening and metal detection before being allowed in. 

Since London was subjected to bomb attacks in July this year, explosive detection in Westminster is becoming more important. Advances in sensing devices for explosives (see Chemistry World, September 2005, p7) could see chemists playing a role in protecting parliament in the future. 

Modern bangs 

As for explosives, gunpowder is still used today, mainly in fireworks - which is appropriate given the pyrotechnic celebrations that still happen in England every 5 November. For small arms guns, gunpowder has been superseded by smokeless powder.  

Military explosives have also moved on. ’TNT (trinitrotoluene) is an explosive where the oxidant and the fuel are part of the same molecule, rather than in black powder where you take a mixture of inorganic materials, an oxidant and a fuel (the fuel being sulfur and charcoal) and mix them together,’ says explosives expert Smith.  

The mechanism of explosion has also changed. Modern high explosives are detonated by the action of a supersonic wave propagating through the material rather than by direct fire. The detonation is triggered electronically. This is in contrast to gunpowder, which is so sensitive to sparks that a cartoon depiction of a gunpowder trail leading to a barrel that goes ’boom!’ is fairly accurate. 

Frightening possibilities 

The question remains: what if the 1605 plot had been successful? If the gunpowder had been well made and stored correctly, the plot might have worked. And if this were the case, the ensuing explosion doesn’t bear thinking about.  

In the 1980s a study estimated that 36 barrels would have contained 2500kg of gunpowder, five times more than was needed to demolish the building. According to Smith, modern legislation dictates that to store this much gunpowder in a brick building you would need 147m between the gunpowder and a footpath, 221m to a minor road, and 442m to a major road or dwelling. 

There is no doubt that the intent was to cause a big bang. As Hunneyball says, ’it was a very audacious bid - they got very close’. 

Further Reading

• J Akhavan, Chemistry of explosives (2nd edn), 2004, RSC, Cambridge, UK