You can contact me at rogercdavies(atsquiggle)

This blog has evolved into a review of historical and modern explosive devices, and responses to them. Links are drawn between historical activity and similar activity in the world today. Mostly I focus on what are now called IEDs but I have a loose personal definition of that and wilingly stray into discussions of more traditional munitions, the science and technology behind them, tactical employment and EOD responses. Sometimes it's just about interesting people in one form or another. Comment is welcome and encouraged but I do monitor it and reserve the right to delete inappropriate stuff. Guest posts are always welcome. Avoid any stuff that makes the enemy's job easier for them.


Entries in HME (2)


Warflour, Paxo and Irish Cheddar

I’ve been doing more research on the IEDs used by the Irish “volunteers” between 1919 and 1922 and found some interesting aspects.   One should remember the time-line of Irish Republicanism that these events of 1919-1922 sit on - Irish revolutionaries were using explosive devices much earlier, certainly as early as 1803, IEDs were used extensively by the Fenians in the latter half of the 19th century, again in 1939 and of course from 1970 onwards.   The window of 1919-122 is just one point on the time line, but is worthy of study for all that.
Firstly, explosives, and I apologise for being somewhat circumspect in the detail here - no need to give modern day revolutionaries with other causes the full recipes. EOD folk can approach me directly of course and I'll point you in the right direction if I know you. At the beginning of the campaign the explosives used was gelignite stolen from quarries, along with “No 6” detonators.  This supply began to become more difficult to obtain and so the Irish volunteers identified chemists and pharmacists and those with military experience from WW1 to develop home made explosives (HME).  There were three types, each given a nickname. I won’t describe their manufacturing process:
“Warflour": Warflour was a nitrated resin, using the ingredients of resin, flour, acid and potassium chlorate.
"Irish Cheddar”:  This was the nickname for a form of cheddite, an explosive used quite extensively in the early 20th century, its ingredients being potassium chlorate, nitrobenzene and castor oil. Some sources suggest that “Cheddar" included home made DNT.  As an aside, this HME was used extensively by the Polish underground in WW2 in their IEDs, which I’ll write about in a future blog post.
"Paxo". This was a mix of potassium chlorate and paraffin wax.  It was the favoured HME in the 1939 campaign but was developed during this period.
The IRA also developed its own detonators at the time, and I won’t describe them here other than to say that interestingly they were non-metallic and quite an effective design.
In terms of IEDs, and further to my earlier post, the IRA of the time made several thousand grenades, mostly under the Dublin Bicycle shop at 198 Parnell St and latterly at other facilities. It appears that the design of these were copied from the German “Egg” grenade of WW1. These were essentially quite a simple design,small and preferred because they were easier to conceal than a larger grenade.  They used the standard sort of fuze with a spring-loaded fly-off lever.  Occasionally larger improvised grenades were used - this is a diagram of one of them, made by an IRA engineer involved in their manufacture. 
IEDs used for roadside ambushes were usually cylindrical pipes, either drain pipes or preferably the cylinders from a  cart axle, filled with gelignite or HME and electrically initiated.  The IRA of the time were ambushing British troops on the roads and certainly learned the trick of laying multiple roadside IEDs at the same spacing as convoy vehicles.  I can find little record of timed IEDs of the time, but the later 1939 “S-Plan” campaign in Great Britain concentrated on the use of timed IEDs.  The cylinders were closed by two end plates - initially with a bolt running down the central axis, and later by a bolt that fitted to the outside of the cylinder.   Command wire initiated devices of this type were occasionally adapated to be come booby traps by the use of a grenade striker system.   The diagram below, drawn by an IRA man shows one such IED.
Further research into the improvised IRA mortar described in my earlier post has thrown up more interesting facts. The background to the IRA requirement was that their roadside campaign was increasingly forcing the police and military to confine themselves to barracks (today we might call them “FOBs”), and the IRA leadership felt they needed a means to attack these barracks directly.  A number of IRA members had fought in the British Army in WW1 and had experienced trench mortars, either as a user or recipient.   The IRA funded a secret delegation to visit Germany and buy arms on the black market , including a German trench mortar but this mission was unsuccessful.  As a fall-back they asked their engineers to develop a home made mortar based on the British “Stokes” trench mortar.  I’m not sure how closely they followed the design, but the IRA version appears to have been of same calibre as the Mk 1 Stokes mortar (3 inch) and projected  an 11lb mortar bomb, again the same as a Mk 1 Stokes mortar.  It appears that the IRA was able to obtain British Army manual for the Stokes mortar.  the tube was made by Matt Furlong’s brother, Joe, at a railway workshop, and Matt (who later died testing a version of the mortar) made the bombs for it at 198 Parnell St.
Additional research leads me to believe that the additional safety feature in the mortar fuze that Matt Furlong removed before his accident was remarkably similar to a fuze safety feature I saw in 1990 or 1991 - on another IRA mortar.  That’s seventy years apart, and essentially the same safety feature being used on an improvised mortar. 



Alchemy and High Explosives

Alchemy is the pursuit of chemical and occult methods to turn base metals into gold, and was an activity pursued with vigour in the 1500s and beyond, into the 1800s even.  As proto-chemists evolved so the boundary between “occult magic” and “chemistry” started to emerge.  At this time the first ever “high explosive” and  indeed the first primary explosive was developed, what we call today fulminating gold or gold fulminate. The German alchemist Sebald Schwaertzer first mentions fulminating gold in literature in his "Chrysopoeia Schwaertzeriana" in 1585.   Other texts add more detail in the early 1600s.

For those readers not familiar with explosives, gunpowder is a low explosive, where the explosion propagates through the explosive material, in effect, by heat and flame. In high explosive the chemical reaction occurring is propagated by a shock wave, and fulminate of gold was the first chemical compound isolated which exploded in this manner.  Fulminate of gold is also the first inherent explosive compound (gunpowder being a mixture of fuel and oxidizer). As it is 'sensitive" it is also the first primary explosive.

Gold is one of the most stable elements – it doesn’t react with very much and by implication a compound of gold is easy to turn back into elemental gold, meaning the compounds are unstable.

For obvious reasons alchemists experimented with gold compounds. They mixed gold with other materials and sometimes accidentally produced compounds that surprised them. It’s tricky to make sense of the archaic descriptions, and the peculiar mixture of occult spells (barking mad) and real chemistry.

Fulminate of gold is created by dissolving gold in “aqua regia”, a three to one mix of hydrochloric acid and nitric acid.  This creates gold hydroxide. When this is mixed with ammonia, gold fulminate is precipitated.  But there are other recipes, which as someone who has a slightly limited expertise in chemistry I simply don’t follow. Real chemists feel free to correct me!   This sensitive explosive is then dried, and can be exploded by heating, crushing or scratching.  This must have been a remarkable thing when first experienced by alchemists who expected the weird and the wonderful.  The chemistry is quite complex and there are a number of related compounds, including (ClAuNH2)2NH and (OHAuNH2)2NH.  Essentially though, fulminate of gold is a mixture of various compounds of ammonia and gold, each of them technically a high explosive.

Fuliminate as a term simply means “exploding” . So gold fulminate can be a mix of a number of complex gold compounds including gold hydrazide.

A number of alchemists and later chemists were injured as a result of experiments with fulminate of gold.  Even in recent years, the research into exotic gold based catalysts has occasionally caused accidents in modern laboratories where gold fulminate was created. 

Here’s the diarist Samuel Pepys describing a conversation on the subject in 1663:

Up and to my office all the morning, and at noon to the Coffee- house, where with Dr. Allen some good discourse about physique and chymistry. And among other things, I telling him what Dribble the German Doctor do offer of an instrument to sink ships; he tells me that which is more strange, that something made of gold, which they call in chymistry Aurum fulminans, a grain, I think he said, of it put into a silver spoon and fired, will give a blow like a musquett, and strike a hole through the spoon downward, without the least force upward; and this he can make a cheaper experiment of, he says, with iron prepared.

Note that “Dribble” is the inventor Cornelius Drebble, who invented the submarine and coincidentally mercury fulminate. Drebbel had died about 30 years prior to this Pepys reference. Some sources suggest that Drebble was using fulminate of gold as a detonator in IEDs (“petards”) he made for the British at the siege of La Rochelle in 1628. Drebbel was thus perhaps the first man to use high explosives in munitions. Drebble’s father-in-law was an alchemist who lost the sight in one eye from an alchemical explosion. (Pepys had other discussions with Drebbel’s son in law, Johannes Kuffler who was trying to sell an explosive device to sink ships - more on that in a future post.)

The gas produced when fulminate of gold explodes is largely nitrogen. Accompanying the gas is a characteristic violet/purple plume of gold aerosols.