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a new theory


What sort of rum would have been traditionally used when doing a 'Gunpowder Test'? It would have been a good, strong rum with a high 'alcohol-by-volume' percentage.


This abv is frequently given a very specific value of 57%....Or not - this value is actually 'Navy Strength', which is a sub-set of spirit definition within the much looser category known as 'over-proof'. 'Navy Strength' is something specific, 'over-proof' is not. The famed 'gunpowder test' only calls for over-proof spirit - which frequently meant people would reach for the Navy Strength, which has a certain traditional ring to it, and does pass muster as an 'over-proof' spirit.

Much talk has been made around a thing called the 'Gunpowder Test'. There is one interpretation of this footnote to naval history that has found general accpetance, going on to become part of the folkloric canon, as it were.


But what is, precisely, this 'Gunpowder Test'?


The generally held notion of what the 'gunpowder test' was all about is that it was a means of testing to see if the sailors' daily rum ration had been watered down by the unscrupulous Purser (whose role it was to manage the shipboard supplies so that they lasted the voyage). This was back in the day when one might find oneself as crew aboard a 'ship-of-the-line' in the golden age of sail and empire-building.


The theory goes that only rum above a certain abv will flare when mixed with a small pile of black gunpowder and set afire.


While it is true that the position of Purser aboard a ship was a lonely and unloved one it would be an inaccurate description of Navy life (where the rum ration was a fixture) to suggest that the crew had much say in how he performed his task. 

One has only to read accounts relating to crew complaints about treatment and conditions that lead to the famous mutinies at the Spithead and the Nore in 1797 to realise that complaint was not undertaken over trivial matters.

If the Purser watered your rum... well you took it and pulled your forelock respectfully.


I would like to suggest an alternative explanation of what the rum-gunpowder test was all about: it was to test the quality of the gunpowder.


Aboard the floating gun platform that was a ship-of-the-line the efficient operation of the ship took precedence over the comfort and lives of the crew. Knowing the quality of the ship's supply of gunpowder was rather more important than knowing the alcoholic kick of the crew's 'tot'.


To this end rum (or any high-proof spirit) was/is a useful tool for a reason of basic chemistry:


Saltpeter or potassium nitrate (which is usually around 70% of the make up of black powder) does not dissolve very well in pure alcohol, but it will dissolve in water.


A gunnery officer, knowing this fact, will be able to test the quality of his powder by using the 'gunpowder test' described above. If good quality gunpowder was soaked in 'over-proof' rum and then allowed to dry out again it should flare up when set alight (providing the powder grains are not too spread out).

This is because the high percentage of saltpeter (the most expensive component in gunpowder) will stop the powder grains from dissolving into a black sludge that will not combust (there must be gaps between grains of gunpowder for the oxygen-fed chain reaction to occur).

Poorer quality gunpowder (i.e. that has too much charcoal or sulphur in it) will dissolve on contact with over-proof rum and, when dried out for the test by flame, will be found to be a non-combustible sooty mess.


This, to my mind, is the real story to the 'gunpowder-test' (note that it is called the 'gunpowder-test', not the 'rum-test'). Out of this important trial-and-error quality test probably grew the Navy's insistence on storing 'over-proof' rum for use aboard ship. Under-proof rum would dissolve any and all gunpowder grains (due to the higher water content) leaving the gunners without a proper way to check the chemical make-up of their powder other than by tasting it (not such a crazy notion - potassium nitrate is a food-grade mineral salt - better quality gunpowder would taste saltier than a lesser product).


And how important is it to know the make-up of your powder, you might ask?


Consider the scenario of a gun-crew preparing to fire on an approaching enemy using a cannon loaded with un-tested powder. Should the powder have been adulterated by an unscrupulous supplier it may not ignite (leading to defeat, capture, imprisonment, or worse for the luckless crew). Or the cannon may fire but with the mix being too weak on explosive force leading to the ball falling short of the enemy... Or, in a worse case outcome, the mix may be the opposite and too much for the cannon, leading to an explosion that kills the whole gun crew.


Russian roulette with cannons is not for the faint of heart.



"American State Papers: Documents, Legislative and Executive, of the Congress of the United States: Naval Affairs - 1822"

[The document from which the following is quoted was a sort of nationwide 'stock take' of Navy property - from ships to brass tacks; a 'State of the Naval Nation' as it were]

p.794: under the heading:

"Return of ordnance and ordnance stores, unfit for service, in the United States' navy yard, Gosport, Virginia...


"152 Barrels cannon powder, under proof
1 half barrel cannon powder, under proof
7 barrels priming powder, under proof
6 half barrels priming powder, under proof
18 barrels, cannon powder, damaged
6 barrels powder dust..."


This small entry I found rather fascinating.


What this delineates is the official use of the term under-proof (and, by extrapolation, 'proof' and 'over-proof') with regard to gunpowder in the Navy.


Proof in this context refers to gunpowder being of a combustible nature fit for purpose - i.e. the powder will, when loaded into a cannon and ignited, fire the projectile with the requisite force. 'Under proof' doesn't mean the powder won't combust or is defective (note the entry '18 barrels, cannon powder, damaged').


When testing ordnance (even today) one applies the 'proof-test' - one 'over-loads' a weapon above the standard tolerances and then lets fly. If the weapon doesn't explode or warp then the weapon is declared 'proofed'. It is not necessarily a 'testing to destruction' process. After a weapon has been tested in such a fashion the weapon is given an internationally recognised stamp of quality. Such tests used to be applied to all manner of things aboard ships - from cannons to swords and even rigging - Being on board a ship when it failed its rigging proof-test would have been a hair-raising experience to be sure...


So, what the above document says is that this same concept of 'proof' was applied to what was loaded into 'proofed' weapons. Under-proof gunpowder was not able to generate the required force and was to be rejected - hence its entry here under 'unfit for service'.


This then suggests the interesting concept that gunpowder 'at proof' was gunpowder that gave the required force without destroying the weapon - while 'over-proof' implied something that would destroy the weapon (which was no one's idea of a fun time - except maybe the opposing ship one was firing upon).


...which is a long way of saying, and here I get to the point, that the terms 'under-proof' 'proof' and 'over-proof' in the context of gunpowder usage aboard ships relates not to alcohol strength in the much mythologised 'gunpowder test' but to the relative quality and strength of the gunpowder in that test. THE RUM WAS A TOOL TO TEST THE GUNPOWDER AND NOT THE REVERSE.



So how does this change the story of 'The Gunpowder Test'?



If one takes this different application of the terms 'under proof' 'proof' and 'over-proof' into consideration (as various grades of gunpowder) one gets a very different slant on the myth of the 'gunpowder test'. This test now takes on the role of a test of absorption rates in different grades of gunpowder. This is based on the principle that potassium nitrate (which forms about 75% of most black gunpowder) will not dissolve in pure or high-strength alcohol.


If a low grade or 'under proof' gunpowder is mixed with strong spirit (such as rum) the low potassium nitrate content will allow the granules of powder to turn into a sludge. This mixture will not combust or even flame (neither the alcohol OR the gunpowder is able to maintain the chemical process of 'burning' -  Unless of course you've emptied a prodigious amount or rum over the gunpowder, then it will catch fire because it is mostly alcohol - which is not really a 'gunpowder test', but merely confirms that strong alcohol will burn, which we knew already)


If a decent grade or 'proof' gunpowder is mixed with strong spirit the percentage of potassium nitrate will allow partial dissolving of the granules of powder - this would form a solution that is too oxygen starved for the gunpowder to form a proper chain-reaction, but not so over-absorbed that the rum will not be able to maintain a flame - gunpowder at 'proof' would give a blue flame but no flaring combustion, or only a spluttering one.


And, finally, if 'over proof' or high-grade gunpowder is mixed with strong rum the granules will retain their shape fairly robustly, the rum will pool at the bottom of the pile and the gunpowder will flare up prodigiously with a proper explosive chain-reaction. The rum below may or may not catch flame depending on its strength and the heat generated by the gunpowder's explosion (it is, after all, possible to extinguish a match by plunging it quickly into high-proof rum and still not get a blue flame - heat and oxygen being more important than a spark in most cases).


[In these days of machine-assisted quality control - any black gunpowder one finds will be of this 'over-proof' variety - no business will wittingly sell something that might hover at the 'proof' category or below. Also note: in all of these instances the various grades of gunpowder - 'under proof', 'proof' and 'over proof' - the gunpowder will still explode when used in the normal fashion (unless it's really badly made) - the 'gunpowder test' is a clever way to assign grades of quality]


In all of these instances (which matches exactly the process of the famed 'gunpowder test') the alcoholic strength of the spirit used is not important. The rum need only be 'strong' - which all good pirates know.


The gunpowder test is an efficient method for testing gunpowder, and a terrible method for testing alcohol strength.


Feel free not to be fascinated by this - it won't, after all, change the way you eat breakfast or pour your rum (unless you're Blackbeard) - but to me this puts the concept of 'proof' in a different light - one where the definition is of explosive force and not alcoholic strength.




"151 shackles, feet and hand, requiring repair"

"1,144 cutlasses requiring repair
1,660 cutlasses unfit for service"


This is Virginia in 1822 after all...





Smoke & Oakum

SINCE 2007


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