Serpentine Gunpowder
 and the guns that used it.

Geoff Smith

Much has been written on where and when gunpowder was first introduced. This paper offers a credible hypothesis to explain why and how the unique mixture may have come about.

Medieval gunpowder recipes of potassium nitrate (KNO 3), charcoal (C), and sulfur (S 8) were investigated by bomb calorimetry to determine their enthalpies of combustion and by differential scanning calorimetry (DSC) to determine their preignition and propagative ignition enthalpies. Various sample preparation methods and several additional ingredients were also tested to determine any effects on the thermodynamic values. Gunpowder recipes were prepared and used in a replica cannon that was manufactured and operated according to medieval records. Post-firing residues were collected from the bomb calorimeter and the cannon in efforts to further characterize recipe energetics using DSC. In general, during the period of 1338−1400, the %KNO 3 increased, and heats of combustion decreased, while between 1400 and 1460, the %KNO 3 decreased, and heats of combustion increased. However, since KNO 3 was usually found in the post-bomb calorimetry and post-cannon firing residues, it was not the limiting reactant. The highest pre-ignition and propagative ignition energies occurred when the KNO 3 :S 8 ratio was 3:1 as determined by DSC, and the highest enthalpies of combustion were measured for recipes where the KNO 3 :C ratio was 1:1 as determined by bomb calorimetry.

Saltpetre in medieval gunpowder; Calcium or Potassium Nitrate? Until recently, it has been accepted that the formulation of gunpowder has always been based on variable mixtures of charcoal, sulphur and potassium nitrate. This has recently been challenged. It has been asserted that early gunpowder was based on lime saltpetre that is calcium nitrate. This paper examines that claim.

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Serpentine Gunpowder and the guns that used it.

Geoff Smith

The earliest gunpowder, known as serpentine, is frequently mentioned by authors. It is said to have easily separated into its constituents in transit, readily absorbing moisture and lacking power. The origin of these assertions is obscure but they are faithfully repeated by each successive generation of author. No original source is cited and it reflects poorly on the scholarship of authors that no attempt has been made to verify theseclaims. This paper attempts to examine the facts in the light of current knowledge of powder handling technologies and ballistics. Although the energy potential depends only on the ratio of ingredients, the burning characteristics of serpentine powder are radically different from later, corned, powder and the influence of this on gun design is explored.

Key Words: Gunpowder, serpentine, corned, bombard, culverine, sling, artillery, ordnance,ballisticsThis paper investigates the early form of gunpowder commonly known as serpentine. Some of the widely believed properties of this materiel are questioned and it is argued that the flame dynamics of serpentine powder differ fundamentally from that of corned powder and has specific influence on the design of early guns. The very earliest form of gunpowder, named proto-gunpowder by Needham, was of indeterminate composition and probably mainly used as an incendiary. As the technology evolved and artillery became a practical battlefield weapon gunpowder was listed in early inventories as simply powder. But as guns diversified to fill different tactical roles we find listings like

puluoris pro gunnis or puluoris pro cannonis

although it is never clear if these are alternative names for the same powder, powder matched to a specific type of gun or simply a stores allocation for an intended use. In the first quarter of the fifteenth century, moist gunpowder was forced through small holes and the resulting crumbs dried to to form what was known as corned powder. The superior properties of corned powder are much advertised by modern historians but the fact remains that the earlier un-corned powder known now as serpentine remained in common use for a further century. From the eighteenth century, gunpowder was commonlycompressed into slabs and then broken down into grains of graded sizes. The few comparative investigations are almost entirely based on this latest form and comparison with serpentine powder consists of largely unsupported assertions.Researching serpentine

gunpowder leads inevitably to its association with the classof fourteenth/fifteenth century gun known as a serpentine. Since the powder was evidently named after the gun, it is reasonable to consider the etymology of the gun first.Rapid developments in artillery in the fifteenth century demanded some sort of formal identification system. In Germany and the low countries, guns were often named after their 1Tout passim.

German

Schlangenpulver

, See below.

use or the projectile they threw, thus

steinbuchse

klotenbuchse

etc. France and the Low countries on the other hand favoured reptiles and mythical beasts,

basilisk

falcon, robinet

etc. and these were largely followed in English usage. The range of calibres and lengths was bewildering and not always easy to define in modern terms

. The serpentine

is a member of a group of guns known as culverin and it is interesting thatthe name derives from the Latin

colubrinus

, a snake. They are light, portable guns used both on land and sea albeit with different mountings. Although in modern usage 'serpentine' suggests a sinuous form, a snake is characteristically long and slim which reasonably describes this class of gun. How this design derives from the properties of the powder will be considered later.St Remy states that the French had serpentine guns at Agincourt (1415) and could account for the English archer, Richard Hunt, recorded as having been killed by a gun at that battle although the presence of artillery at the battle is disputed by some authorities.English warships were carrying such guns in 1490 . Tower inventories first list serpentine powder by name in 1523 although it was presumably the same material as previously simply listed as

gunne poudr

(sic) with various spellings.

Cornepowdre

is first separately listed by the Tower in 1540

although it is generally accepted that it was first developed about 1450. This can only be taken as an approximate indication of dates as the Tower was not the only a powder store and the component materials were frequently issued for local manufacture. The name was still in use in 1798 see footnote (12)The Tudor warship Mary Rose provides a unique insight of naval guns of the time. Her armament was recorded at the time and guns recovered from the wreck have been extensively researched and throw some light on aspects of the serpentine gun and powder.For instance in 1514 the armament of the Mary Rose

included serpentines

but by 1545 these had disappeared to be replaced by 'slings'. The German piece of the same era called a

Schlange

also translates as snake and could well be the origin of the slings carried by the Mary Rose and recovered examples show all the characteristics of a typical serpentine. It is difficult to avoid the conclusion that these are the same or similar guns. Perhaps there was a German gunner in the crew who preferred his native name. Reliable dimensions of the serpentine are elusive but a calibre of 1.5 inches with a barrel length circa 20-25 calibres is a reasonable consensus

and it has been suggested that the name derives from the long slim snake like appearance of the barrel

. Tower inventories initially list the similar Robinet as having a calibre of 1.25 inches but later as 1.5 inches at about the time that the serpentine disappears from the lists

. Both are 3 The ordnance of the fourteenth and fifteenth centuries. R. Coltman Clephan, f.s.a.4Serpentine is an adjective but no trace of a 'serpent' has been found in this context although Tout refers in passing to 'serpent guns'.5Brackenbury6The preserved Tudor warship sunk in 15457 When the Mary Rose sank in 1545, she was carrying both serpentine and corned powder MR had 2 last of serpentine powder in barrels (c. 2180 Kg) and only three barrels of corned (236Kg), but not specified whether gross or fine. Her weapons included 15 bronze guns 24 large wrought iron , 20 cast iron hailshot pieces, 2 top pieces, 30 bases and 50 handguns but no named serpentine guns. Weapons of Warre Ed A. Hildred8Brackenbury, Tout et.al.9Oddly, the well known contemporary musical instrument of the same name has a shape more representative of the modern concept of serpentine.10 Brackenbury

associated with lead ball projectiles and the name change could simply reflect fashion or a rationalisation of the inventory. A further important characteristic is an absence of reinforcement in the breech area.The serpentine gun has long been associated with serpentine powder but evidence suggests that the powder was used in other guns of that general class. For example the Mary Rose carried mainly serpentine and a lesser quantity of corned powder; far more than required to serve the six serpentine/slings mounted. Reliably identified examples of guns specifically identified as a 'serpentine' are rare and this will be considered later.

Serpentine Powder

Serpentine powder is understood to imply a fine mixture of potassium nitrate, sulphur and charcoal mixed in proportions rather less efficient than the later accepted norm of 75:15:10 but evolving towards that over the years. The particle size has been described as similar to modern talcum powder, i.e. dust, although contemporary sources describe it as like flour. This would have been the only type made until the introduction of knollenpulver

and its evolution into corned powder. Powder of this type was thus available and in use long before the introduction of the serpent type gun and continued in use long after the introduction of corned powder, the two types frequently appearing together in armoury inventories. As late as 1798 Tax was being imposed on both import and export of serpentine powder

and the name lives on as the Serpentine lake in London, created 1730 for Queen Caroline.

It has long been received wisdom that serpentine powder suffered from several defects. One of these was its propensity to separate into its component parts if subjected to vibration when transported over the poor roads of the period and It is commonly stated that sulphur, being the most dense, would migrate to the bottom of the barrel. However, the actual densities are :-Saltpetre, 2.11 g/cc Sulphur c. 2 g/cc depending on the allotrope.Charcoal is largely composed of carbon c. 2 g/cc The actual bulk density of charcoal, depending on the wood type etc., is in the region of 0.2 g/cc due to the air trapped in the pores and between the particles. Grinding charcoal to a fine powder reduces the entrained air tending to a limiting case density nearer to that of pure carbon. The difference in densities is evidently trivial and cannot account for any segregation.11Small cakes of powder are first mentioned in the Firework Book pre 1400 but there is nomention of its deployment in guns. Kramer asserts that the cakes were broken down before use but offers no evidence.12 ..." a duty of one pound two shillings be charged on every One hundred Weight of Serpentine Gunpowder imported ..... and .. a Drawback of nineteen shillings and six pence be allowed on every One hundred weight of Serpentine Gunpowder exported ... from this Kingdom. Journals of the House of Commons, Volume 42 Resolution 1093, 1094Journals of the House of Commons, Volume 42, 178713 The site of a former gunpowder store, it is now the Serpentine Sackler art gallery.

Any movement of individual particles in the body of a barrel of powder would be restricted by the mass of powder above and transport, however violent, would be unlikely to fluidise the bulk. In the case of transport by sea, even the most violent storm produces little in the way of vibration and simply rocking a barrel of powder produces no movement in the bulk. Serpentine powder particles exhibit cohesive properties, immediately apparent when attempting to pour it

and this would severely restrict any movement within the bulk. See Tartaglia's comment below. By comparison corned powder pours readily and this difference is reported by Tartaglia. A further mechanism that is said to effect separation is well known as the 'Brazil nut effect'. This results in smaller particles descending and is largely independent of density difference. For illustration, consider a marble dropped onto a stack of footballs where it would easily fall through the interstices whereas a tennis ball would not. In a finely ground serpentine where particles are of very similar size, this mechanism too lacks credibility. Powder mixing and segregation are common in modern production chemistry and have been extensively studied. Much research effort has been directed at powders handled in the pharmaceutical industry and this is particularly relevant as each of the constituents of gunpowder have application in modern formulations. Although serpentine powder for artillery use was largely superseded by corned powder during the sixteenth century, much of the powder used in modern pyrotechnics (now called mealed powder) is not corned or granulated and no such separation is reported in the industry. In the absence of credible contemporary reports, this reasoning must be dismissed. It would appear the this is another instance where a technically inept writer has made an assertion which has been repeated endlessly, presumably in the nameof historiography.

It is also worth noting the corned powder is soft compared with later compressed powder. The grains are easily crushed and broken down by abrasion and its performance is thus susceptible to change as a result of vibration in transport producing a proportion of dust. This is not reported as a problem to gunners over the many years when corned was the standard powder and appears to have been a well known and accepted as a minor unavoidable nuisance. As late as 1855 Lieut.-Col. J. S. G. Kevlay, Bengal Cavalry reported '

.....the great loss experienced when gunpowder is transported by land carriage in barrels, especially over the rude tracts in some parts of India, causes it to be much ground down tofine dust, which falls to the bottom of each barrel.'

This of course refers to corned powder but could well be the origin of the urban myth that serpentine separated in transit. Although fourteenth century inventories list ready made gunpowder, the practice of mixing powder 'on site' was common. This can be explained by either safety considerations or the concern of master gunners to be in control of the proportions. Indeed, in time of conflict, the only person competent to manufacture powder, the master 14 Author's observation

15This problem is not new. In 1632 Galileo wrote of those who ..."put faith in their predecessors , right on back without ever arriving at anyone who had performed it.....

for anyone who does it will find that the experiment shows exactly the opposite of what is written

..." Galileo Galilei, Dialogue concerning the Two Chief world Systems – Ptolemeic and Copernican, trans. Stillman Drake, University of California Press, 1953.

gunner, would be with his guns with the army. Even if segregation of powder in transit hadactually occurred, it would have been far simpler to re-mix the batch on site without havingto accurately weigh the components individually as they would already be in the correct proportions. In practice, a battlefield is no place to carry out accurate weighing and gun charges in the field were invariably dispensed by volume.In an attempt to reproduce the separation effect a sample of modern 'serpentine' powder was placed in a tube so as to represent a vertical section of powder in a barrel. The tube was fitted with a vibrating device and shaken for several hours. At the end of the experiment no difference in either appearance or burn rate was detected between samplestaken from both top and bottom of the sample. Another reason frequently given for the demise of serpentine powder is that it absorbs water more readily than corned powder. The reasoning offered is that a finely divided powder has more surface area than the same mass granulated. This might be credible if the powder was uniformly exposed to damp air in a thin layer but, contained in abarrel, the exposed surface area is tiny compared with corned powder where air can circulate freely between the grains. Since water absorbed by powder is largely entrained inthe pores of the charcoal

, the inherent potential for moisture uptake is largely independent of the grain size. In any case, the argument would only affect the rate of absorption and not the total amount absorbed. Serpentine powder was carried aboard the Mary Rose and a Tudor warship could certainly not be called a dry environment. Even later in 1588 Tartaglia records large scale manufacture of serpentine powder in the Arsinale of Venice, again a largely maritime user. In the absence of contemporary evidence, this appears to be another assertion supported only by frequent (modern) repetition.One astonishing statement is found in the literature

. Viz.

"Although the use of potassium nitrate and the addition of wood ashes were both meant to keep the saltpeter as dry as possible, the gunpowder made in this way (later called serpentine powder) remained soluble"

This is self evident nonsense. Saltpetre is always readily soluble in water and no amount of modification will change that. Sulphur is only appreciably soluble in carbon disulphide and carbon only dissolves readily in molten iron!It is remarkable that at least two largely maritime nations, England and Venice were both using serpentine powder a hundred years after the introduction of corned powder.Tartaglia/Lucar

provides at least a partial explanation. In the style of the time, this is reported as a conversation between himself and a gunner (Jerome) discussing why cornedpowder is used in handguns and harchibse (sic.) but mealed powder in great ordnance. One reason given is that uncorned powder tends to clog the nozzle of priming flasks

. Again, a major maritime power continues to use serpentine in parallel with corned powder without comment on its sensitivity to moisture.16 Charcoal was employed as a water absorbant to keep powder dry. For instance the powder magazine of HMS Victory had floor and walls lined with charcoal.17 The Cambridge History of Science: Volume 3, Early Modern Science edited by David C.Lindberg, Roy Porter, Katharine Park, Lorraine Daston, Mary Jo Nye, Theodore M. Porter, Dorothy Ross18 158819 In filling 5mm paper tubes with various powders to compare burn rate, the Author observed that modern glazed powders flowed like liquid, corned powders needed a little shaking but serpentine clogged the funnel repeatedly.

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Serpentine Gunpowder and the guns that used it.

Serpentine Gunpowder and the guns that used it.

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