The Pitch Drop Experiment

Bernard O’Donoghue’s poem “What’s the Time, Mr Wolf?” in his collection Gunpowder (1995) opens with a snatch of hearsay about the amorphous inorganic material that casts its lustre on our lives: 

Glass, someone once told me, is a liquid
Of such density that its sluggish
Downward seep takes centuries to work,
So medieval windows are thicker
At the bottom than the top. 

To imagine that old glass flows imperceptibly, much as we imagine time itself flowing, is a beautiful conceit; alas, like most poetic ideas, it isn’t true. It’s like the belief, which persisted into the twentieth century, that as pressure increased with depth the sea became more solid: in the deeps of the oceans there were “floors” on which sunken objects gathered according to their weight.

O’Donoghue goes on to reflect—more plausibly—that our flesh is subject to the same gravitational pull as cathedral windows, sagging as the years pass: “It creeps for the earth …” The German poet Gottfried Benn said the same thing, more laconically, in one of his expressionist poems: “Earth calls.” Our lives aren’t time-reversal symmetric; and our bodies sometimes not even especially shapely. They perdure a few years, but with ever less buoyancy. And though we can never perceive time with our senses, we notice from the evidence of change around us that we must be living in it. So O’Donoghue’s poem is actually a memento mori, a perfectly respectable theme for a poet to address.

Gravity doesn’t “relax” glass. Vitreous silica at room temperature is as mechanically unremarkable as other solids, except for being a bit brittle. And while it is true that old windows are often thicker at the bottom than the top, the observation is based on a false assumption: the glass made by the original glassblowers was never uniform to begin with. It was made by the crown glass process, in which the molten silica is spun to form a plate; commonly the edges of the disc became thicker as the glass was spun. This was beneficial: a thick bottom edge gave added stability, and prevented rainwater collecting inside the lead cames that were applied to the wooden framework to hold the glass in place. Early mass production using cooling tables also produced unevenly thick panes of glass, so the phenomenon is by no means solely a pre-modern one.

There is one substance, however, which is obdurately solid but has liquid properties: tar pitch. In one of the longest-running experiments in history, Thomas Parnell, professor of physics at the University of Queensland, set up a simple device in his lab in Brisbane to demonstrate to his students that pitch or bitumen—the naturally occurring petroleum extract used as mortar, according to Herodotus, in the walls of Babylon, and as waterproofing for medieval ships and modern roofs—is actually fluid (a viscoelastic polymer) although it looks just like a lump of coal. Blocks of pitch will even shatter, like glass, if subjected to a hard blow.

In 1927, Parnell heated a sample of pitch and decanted it into a glass funnel with a sealed stem. The pitch was allowed to solidify in the funnel over three years, and then the seal was cut. The experiment proper was now under way: at room temperature the pitch began to seep through the funnel. It was hardly in a rush: pitch is a fluid of such sluggishness that all Parnell’s students had long since left his class and graduated when the first drop fell. Parnell himself died in 1947. Eight decades later, only eight drops have collected in the beaker placed beneath the stem. The experiment still has over a century to run.

The apparatus—which is the very model of low maintenance equipment—is currently displayed under a bell-jar in the foyer of the Department of Physics; nobody has ever witnessed the fall of a drop, although that may change now that the experiment can be viewed by web camera. Actually, it might be more instructive to watch grass grow, since the interval between each drop has lasted from seven to twelve years. Pitch, under normal atmospheric pressure and even at the relatively high annual temperature of southern Queensland, is more than a hundred billion times more viscous than water. 

Had he known about it, I suspect the composer John Cage would have been greatly intrigued by the simplicity—and the audacity—of the pitch drop experiment. One of his younger colleagues, George Brecht, a member of the international Fluxus movement, wrote an “event score” called Drip Music, first presented to the public in 1963, in which “a source of dripping water and an empty vessel are arranged so that the water falls into the vessel”.

In a different register, slowness supplies the organising conceit of two recent novels: Milan Kundera’s Slowness (1993), an essay disguised as a story that ties our “fear, revulsion and horror” (Walter Benjamin) with modern life to its press and speed and suggests that purposeful remembering, on the other hand, is contingent upon slowness; and Sven Nadolny’s best-selling German novel Die Entdeckung der Langsamkeit (1983), which follows that stubbornly individualistic explorer Sir John Franklin in his fatal attempt to find the North-West Passage in the remote Arctic “where nobody would find him too slow”. Nadolny’s book is now recommended reading on contemporary management courses that want to hoop environmental sustainability within systems thinking.

Much more recently Don DeLillo touches on slowness in his fable Point Omega, which has one character in a New York gallery watching Douglas Gordon’s film project, 24 Hour Psycho, a slowed-down video installation of the notorious shower scene from Hitchcock’s film, and another stubbornly seeking to move beyond the super-personalised highest stage of consciousness (towards which all sentient life is striving, according to Pierre Teilhard de Chardin) into something inorganic and rocklike.

But neo-Dada performance pieces and speculative “transhuman” novels are way too tidy and efficient (the very brevity of Kundera and DeLillo’s novels suggests their authors are perhaps more on the side of speed that they would accept) in comparison to the metaphysical implications of allowing a clump of pitch in a laboratory in Australia to extrude a drop of itself once a decade, give or take a few years. Nothing really happens, we might think, and yet the evidence is there to see in the bottom of the beaker: all that is solid doesn’t necessarily melt into air—sometimes it turns out to be in flux. Very slow flux.

Slowness doesn’t mean standstill: it is the music of what takes “centuries to work”. Evolution hasn’t equipped us with a sense organ for appreciating geological time. It is our failure to appreciate the slow flow of the pitch drop experiment that gives us an odd sense of vertigo when we encounter it for the first time. Slowness, according to the German cultural historian Heiner Mühlmann, “is a movement that lasts longer than a generation. To observe it, we need to work together with people who lived before us and people who will live after us.” Recent historical practice has turned away from the grand old narratives of universal history to imagine interior life behind the windows of ordinary houses. The sediment of these micro-histories is the event, pregnant with its own immanence. If every single thing connects, if one event contains the germ—molecule or monad—that might account for another, then the remembered world is bound to come to seem sluggish and compacted. As dense, perhaps, as a lump of pitch.

Our failure to grasp the true nature of slowness, Mühlmann suggests, is what we call “transcendence”. On the other hand, the British idealist philosopher R.G. Collingwood once formulated what he called the “substantialist fallacy”, which consists in extracting from a simple chronological sequence a continuous transcending “something”. And that doesn’t just apply to the creep of days across the windowpane, but when time itself falls away, into epochs. 

Iain Bamforth lives in Strasbourg.