Prince Rupert's Drop

A Prince Rupert's Drop
Prince Rupert's Drops offer very suggestive metaphors for the state of a society in a moment of both extreme resilience and potential fragmentation. The drops appeared in England during the seventeenth century immediately after the Restoration of the English monarchy. Charles II was interested in the new sciences that were emerging and was familiar with many of the scientific controversies of the day, Prince Rupert too was fascinated by new scientific discoveries and curiosities. Indeed, in 1660, the Royal Society was granted a royal charter by King Charles II and whose scientific activities caused great interest across English society. For example, Samuel Pepys mentions the drops in his diary of 13 January 1662, as "chymicall glasses, which break all to dust by breaking off a little small end; which is a great mystery to me" (Pepys 1662).

The Prince Rupert's Drop (Lacrymae Vitreae) is a scientific oddity, originally thought to have emerged when glass was melted and perhaps accidentally released into water, which was always found near the furnaces for glass-blowers (Beckmann et al 1846: 241). As Brodsley et al explain, a sense of mystery permeates the history of Prince Rupert's Drops, which they link to the fact that since the time of Emperor Tiberius glass-blowers might well have had a taboo about mentioning information about glass to outsiders as Tiberius had ordered the inventor of toughened glass to be put to death to prevent it being communicated to others. When molten glass is dropped into water in a particular way, it forms what look like glass tears, or tadpole shaped glass beads. The beads themselves, together with their tails of glass, have some extremely odd properties, which when they came to the attention of experimental philosophers in the middle of the seventeenth century caused much excitement.
The 'bubbles'-the solid ones, at least-were what were later to called 'Prince Rupert's drops'. (Those said to contain 'liquor' could have been something different, but were probably the same containing vacuoles and no actual liquid.) These objects, glass beads with the form of a tear- tapering to a fine tail, made (though that was not generally known at the time by dripping molten glass into cold water, exhibited a paradoxical combination of strength and fragility not without interest to the materials scientist of the present day, and which could not fail to excite the imagination of natural (and not so natural) philosphers of the I7th century. The head withstands hammering on an anvil, or, as a more modern test, squeezing in a vice indenting its steel jaws, without fracture: yet breaking the tail with finger pressure caused the whole to explode into powder (Brodsley 1986: 1).
Prince Rupert
Beckmann et al explain that the beginning of the scientific examination of these glass drops is somewhat clouded in history, with evidence that they were made in The Netherlands in 1656 (and hence their other name as Dutch drops), and displayed in Paris and other cities to much interest (although some thought they had emerged from Sweden rather than The Netherlands). Brodsley dates their earliest date to the Mecklenburg glass-houses before 1625 (Brodsley 1986: 5-6). Nonetheless, their name became associated with Prince Rupert who bought them to England as gifts for Charles II, and which were given to the Royal Society. Prince Rupert returned to England from Germany in 1660 to join with Charles II after the Restoration in 1660. They were experimented with at the Royal Society in 1661 and examined by Robert Hooke (1665) and Thomas Hobbes (1662). According to the minutes of the Royal Society, "the King sent by Paul Neile five little glass bubbles, two with liquor in them, and the three solid, in order to have the judgement of the society concerning them" (Brodsley 1986: 1). In 1663 even Samuel Butler referred to them in his poem, Hudibras,
Honour is like that glassy bubble
That finds philosphers such trouble,
Whose least part crack'd, the whole does fly
And wits are crack'd, to find out why.
The way in which the drop's head is formed into a state of tensile stress creates a remarkably strong material surface, which cannot be cracked with a hammer, or even with a bullet.[1] However, should the tail be given the slightest crack, the entire structure disintegrates into an explosion of glass due to the high potential energy stored through the tail. It was not until A. A. Griffith's research in 1920 that,
the qualitative ideas of the strengthening effect of compressive stress could be given a detailed and mathematical formulation. In Griffith's theory, the fracture of a brittle substance, such as glass, is initiated from pre-existing microcracks, which can grow larger, extracting enough elastic energy from their surroundings to pay for the energy of the increased area of free surface only if the stress around them is tensile and the product of the stress and the square root of the crack diameter exceeds a critical value dependent on basic properties of the material. (Brodsley 1986: 2).
This curious way of fragmentation and explosion of the drop from a tiny crack in the tail, but the incredible resilience in the head of the drop led to many analogies being formed from its example. For example, as early as 1671, Geminiano Montanari who sent a paper to the Royal Society on the subject of the Prince Rupert Drop, concluded his paper saying "so is a kingdom one and strong but when the top is broken shivers into men" (McManus 2014). Similarly, in 1851, in his Address to the Citizens of Concord on the Fugitive Slave Law, Waldo Emerson remarked that Daniel Webster, a Massachusetts senator elected by the Whig party, thought,
that the American Union is a huge Prince Rupert's Drop, which, if so much as the smallest end be shivered off, the whole will snap into atoms. Now, the fact is quite different from this. The people are loyal, law-abiding. They prefer order, and have no taste for misrule and uproar (Emerson 1851: 182).
Indeed, Freud in Group Psychology and the Analysis of the Ego (1921) contemplated "the loss of the leader in some sense or other, the birth of misgivings about him, brings on the outbreak of panic, though the danger remains the same; the mutual ties between the members of the group disappear, as a rule, at the same time as the tie with their leader. The group vanishes in dust, like a Prince Rupert’s drop when its tail is broken off" (Freud 1921).

At a time when there appears to be a rise in authoritarianism and popularism, and the strong identification with a leader, this metaphor provides a way of thinking about the political unity of contemporary constellations of reactionary political movements. The Prince Rupert's Drop perhaps becomes useful again as a metaphor to think about the possible effects of this kind of political sensibility. But whether it is the new political constellations themselves or society as a whole that fragments when the tail potentiality is released, depends ever more on the political sensibility, levels of rationality and critical reflexivity of a public which under conditions of computational capitalism looks increasingly unprepared in a digital age.


[1] See for a 130,000 frames per second video of the Prince Rupert's Drop as it explodes.


Beckmann, J., Johnston, W., Francis, w., Griffith, J. W. (1846) A history of inventions, discoveries, and origins, London, H.G. Bohn.

Brodsley, L., Frank, C. and Steeds, J.W. (1986) Prince Rupert's Drops, Notes and Records of the Royal Society of London, Vol. 41, No. 1 (Oct., 1986), pp. 1-26

Emerson, W. (1851 [2005]) Address to the Citizens of Concord on the Fugitive Slave Law, in The Selected Lectures of Ralph Waldo Emerson,  University of Georgia Press.

Freud, S. (1921) Group Psychology and the Analysis of the Ego, London: WW Norton & Company.

Hobbes, T. (1662) Problematica Physica, translated in English in 1682 as Seven Philosophical Problems, pp. 36-39, 146-148.

Hooke, R. (1665) Micrographia or Some Physiologial Descriptions of Minute Bodies made by Magnifying Glasses with Observation and Inquiries thereupon, London: Jo. Martyn and Ja. Allestry.

Pepys, S. (1662) Monday 13 January 1661/62, The Diary of Samuel Pepys, accessed 09/01/2017,


Popular Posts