Uncle Tungsten

18. Cold Fire

My many uncles and aunts and cousins served as a sort of archive or reference library, and I would be referred to different ones for specific problems: most often to Auntie Len, my botanical aunt, who had played such a lifesaving role in the grim days of Braefield, or Uncle Dave, my chemical and mineralogical uncle, but there was also Uncle Abe, my physics uncle, who had started me on spectroscopy. Uncle Abe was consulted rather rarely at first, because he was one of the senior uncles, six years Uncle Dave’s senior and fifteen years my mother’s. He was regarded as the most brilliant of his father’s eighteen children. He was intellectually formidable, although his knowledge had come through a sort of osmosis, not formal training. Like Dave, he had grown up with a taste for physical science, and like Dave, he had gone geologizing to South Africa as a young man.

The great discoveries of X-rays, radioactivity, the electron, and quantum theory had all occurred in his formative years and were to remain central interests for the rest of his life; he had a passion for astronomy and for number theory as well. But he was also perfectly capable of turning his mind to practical and commercial ends too. He played a part in developing Marmite, the widely used vitamin-rich yeast extract developed early in the century (my mother adored this; I hated it), and, in the Second World War, when normal soap was difficult to get, he helped develop an effective fat-free soap.

Though Abe and Dave were alike in some ways (both had the broad Landau face, with wide-set eyes, and the unmistakable, resonant Landau voice – characteristics still marked in the great-great-grandchildren of my grandfather), they were very different in others. Dave was tall and strong, with a military posture (he had served in the Great War and in the Boer War before that), always carefully dressed. He would wear a wing collar and highly polished shoes even when he worked at his lab bench. Abe was smaller, somewhat gnarled and bent (in the years that I knew him), brown and grizzled, like an old shikari, with a hoarse voice and chronic cough; he cared little what he wore, and usually had on a sort of rumpled lab smock.

The two were associated formally as codirectors of Tungstalite, though Abe left the business end to Dave and spent all his time in research. It was he who developed a safe and effective way of ‘pearling’ lightbulbs with hydrofluoric acid in the early 1920^s – he had designed the machines to do this in the Hoxton factory. He also worked on the use of ‘getters’ in vacuum tubes – highly reactive, oxygen-hungry metals like cesium and barium which could remove the last traces of air from a tube – and, earlier, he had patented the use of Hertzite, his synthetic crystal, for crystal radios.

He had developed and patented a luminous paint, and this was used in military gunsights in the First World War (it may have been decisive, he told me, in the Battle of Jutland). His paints were also used to illuminate the dials of Ingersoll watches and clocks. He had, like Uncle Dave, big, capable hands, but where Uncle Dave’s were seamed with tungsten, Uncle Abe’s were covered with radium burns and malignant warts from his long, careless handling of radioactive materials.

Both Uncle Dave and Uncle Abe were intensely interested in light and lighting, as was their father; but with Dave it was ‘hot’ light, and with Abe ‘cold’ light. Uncle Dave had drawn me into the history of incandescence, of the rare earths and metallic filaments which glowed and incandesced brilliantly when heated. He had inducted me into the energetics of chemical reactions – how heat was absorbed or emitted during the course of these; heat that sometimes became visible as fire and flame.

Through Uncle Abe, I was drawn into the history of ‘cold’ light – luminescence – which started perhaps before there was any language to record things, with observations of fireflies and glowworms and phosphorescent seas; of will-o’ – the-wisps, those strange, wandering, faint globes of light that would, in legend, lure travelers to their doom. And of Saint Elmo’s fire, the eerie luminous discharges that could stream in stormy weather from a ship’s masts, giving its sailors a feeling of bewitchment. There were the auroras, the Northern and Southern Lights, with their curtains of color shimmering high in the sky. A sense of the uncanny, the mysterious, seemed to inhere in these phenomena of cold light – as opposed to the comforting familiarity of fire and warm light.

There was even an element, phosphorus, which glowed spontaneously. Phosphorus attracted me strangely, dangerously, because of its luminosity – I would sometimes slip down to my lab at night to experiment with it. As soon as I had my fume cupboard set up, I put a piece of white phosphorus in water and boiled it, dimming the lights so that I could see the steam coming out of the flask, glowing a soft greenish blue. Another, rather beautiful experiment was boiling phosphorus with caustic potash in a retort – I was remarkably nonchalant about boiling up such virulent substances – and this produced phosphoretted hydrogen (the old term), or phosphine. As the bubbles of phosphine escaped, they took fire spontaneously, forming beautiful rings of white smoke.

I could ignite phosphorus in a bell jar (using a magnifying glass), and the jar would fill with a ‘snow’ of phosphorus pentoxide. If one did this over water, the pentoxide would hiss, like red-hot iron, as it hit the water and dissolved, making phosphoric acid. Or by heating white phosphorus, I could transform it into its allotrope, red phosphorus, the phosphorus of matchboxes.[52] I had learned as a small child that diamond and graphite were different forms, allotropes, of the same element. Now, in the lab, I could effect some of these changes for myself, turning white phosphorus into red phosphorus, and then (by condensing its vapor) back again. These transformations made me feel like a magician.[53]

But it was especially the luminosity of phosphorus that drew me again and again. One could easily dissolve some of it in clove oil or cinnamon oil, or in alcohol (as Boyle had done) – this not only overcame its garlicky smell, but allowed one to experiment with its luminosity safely, for such a solution might contain only one part of phosphorus in a million, and yet still glow. One could rub a bit of this solution on one’s face or hands, and they would glow, ghostlike, in the dark. This glow was not uniform, but seemed (as Boyle had put it) ‘to tremble much, and sometimes… to blaze out with sudden flashes.’

Hennig Brandt of Hamburg had been the first to obtain this marvelous element, in 1669. He distilled it from urine (apparently with some alchemical ambition in mind), and he adored the strange, luminous substance he had isolated, and called it cold fire (kaltes Feuer), or, in a more affectionate mood, mein Feuer.

Brandt handled his new element rather carelessly, and was apparently surprised to discover its lethal powers, as he wrote in a letter to Leibniz on April 30, 1679:

But though all the early researchers burned themselves severely with phosphorus, they also saw it as a magical substance that seemed to carry within itself the radiance of glowworms, perhaps of the moon, a secret, inexplicable radiance of its own. Leibniz, corresponding with Brandt, wondered whether the glowing light of phosphorus could be used for lighting rooms at night (this, Abe told me, was perhaps the first suggestion of using cold light for illumination).

No one was more intrigued by this than Boyle, who made detailed observations of its luminescence – how it, too, required the presence of air, how it fluctuated strangely. Boyle had already made extensive investigations of ‘luciferous’ phenomena, from glowworms to luminous wood and tainted meat, and had made careful comparisons of such ‘cold’ light with that of glowing coals (both, he found, needed air to sustain them).

On one occasion Boyle was called down from his bedchamber by his frightened and astonished servant, who reported that some meat was glowing brightly in the dark pantry. Boyle, fascinated, got up at once and commenced an investigation, which culminated in his charming paper ‘Some Observations about Shining Flesh, both of Veal and Pullet, and that without any sensible Putrefaction in those Bodies.’ (The shining was probably due to luminescent bacteria, but no such organism was known or suspected in Boyle’s time.)

Uncle Abe, too, was fascinated by such chemical luminescence, and had experimented a great deal with it as a young man, and with luciferins, the light-producing chemicals of luminous animals. He had wondered whether they could be turned to practical use, to make a really brilliant luminous paint. Chemical luminosity could indeed be dazzlingly brilliant; the only problem was that it was ephemeral, transient, by nature, disappearing as soon as the reactants were consumed – unless there could be (as with fireflies) a continued production of the luciferous chemicals. If chemistry was not the answer, then one needed some other form of energy, something that could be transformed into visible light.

Abe’s interest in luminescence had been stimulated, when he was growing up, by a luminous paint used in their old house in Leman Street – Balmain’s Luminous Paint, it was called – for painting keyholes, gas and electric fixtures, anything that had to be located in the dark. Abe found these glowing keyholes and switches wonderful, the way they glowed softly for hours after being exposed to light. This sort of phosphorescence had been discovered in the seventeenth century, by a shoemaker in Bologna who had gathered some pebbles, roasted them with charcoal, and then observed that they glowed in the dark for hours after they had been exposed to daylight. This ‘phosphorus of Bologna’, as it was called, was barium sulphide, produced by the reduction of the mineral barytes. Calcium sulphide was easier to procure – it could be made by heating oyster shells with sulphur – and this, ‘doped’ with various metals, was the basis of Balmain’s Luminous Paint. (These metals, Abe told me, added in minute amounts, ‘activated’ the calcium sulphide, and lent it different colors as well. Perfectly pure calcium sulphide, paradoxically, did not glow.)

While some substances emitted light slowly in the dark after being exposed to daylight, others glowed only while they were being illuminated. This was fluorescence (after the mineral fluorite, which often showed it). This strange luminosity had been originally discovered as early as the sixteenth century, when it was found that if a slanting beam of light was directed through tinctures of certain woods, a shimmering color might appear in its path – Newton had attributed this to ‘internal reflection.’ My father liked to demonstrate it with quinine water – tonic – which showed a faint blue in daylight and a brilliant turquoise in ultraviolet light. But whether a substance was fluorescent or phosphorescent (many were both), it required blue or violet light or daylight (which was rich in light of all wavelengths) to elicit the luminescence – red light was of no use whatever. The most effective illumination, indeed, was invisible – the ultraviolet light that lay beyond the violet end of the spectrum.

My own first experiences of fluorescence occurred with the ultraviolet lamp my father kept in the surgery – an old mercury vapor lamp with a metal reflector, which emitted a dim bluish violet light and an invisible blaze of ultraviolet. It was used to diagnose some skin diseases (certain fungi fluoresced in its light) and to treat others – though my brothers also used it for tanning.

These invisible ultraviolet rays were quite dangerous – one could be severely burned if exposed too long, and one had to wear special goggles like an aviator’s, all leather and wool, with thick lenses made of a special glass that blocked most of the ultraviolet (much of the visible, too). Even with goggles, one had to avoid looking directly at the lamp, otherwise a strange, unfocused glow appeared, due to the fluorescence of one’s eyeballs. One could see, looking at other people in the ultraviolet light, how their teeth and eyes glowed a brilliant white.

Uncle Abe’s house, a short walk from ours, was a magical place, filled with all sorts of apparatus: Geissler tubes, electromagnets, electric machines and motors, batteries, dynamos, coils of wire, X-ray tubes, Geiger counters and phosphorescent screens, and a variety of telescopes, many of which he had built with his own hands. He would take me up to his attic laboratory, on weekends especially, and once he had satisfied himself that I could handle the apparatus, he gave me the run of his phosphors and fluorescent materials, as well as the little handheld Wood’s UV lamp he used (this was much easier to deal with than the old mercury vapor UV lamp we had at home).

Abe had racks and racks of phosphors in his attic, which he would blend like an artist with his palette – the deep blue of calcium tungstate, the paler blue of magnesium tungstate, the red of yttrium compounds. Like phosphorescence, fluorescence could often be induced by ‘doping’, adding activators of various sorts, and this was one of Abe’s chief research interests, for fluorescent lights were just beginning to come into their own, and subtle phosphors were needed to produce a visible light that was soft and warm and agreeable to the eye.[54] Abe was especially attracted to the very pure and delicate colors which could be made if one added various rare earths as activators – europia, erbia, terbia. Their presence in certain minerals, he told me, even in minute quantities, lent these minerals their special fluorescence.

But there were also substances that would fluoresce even when absolutely pure, and here uranium salts (or, properly speaking, uranyl salts) were preeminent. Even if one dissolved uranyl salts in water, the solutions would be fluorescent – one part in a million was sufficient. The fluorescence could also be transferred to glass, and uranium glass or ‘canary glass’ had been very popular in Victorian and Edwardian houses (it was this which so fascinated me in the stained glass in our front door). Canary glass transmitted yellow light and was usually yellow to look through, but fluoresced a brilliant emerald green under the impact of the shorter wavelengths in daylight, so it would often appear to shimmer, shifting between green and yellow depending on the angle of illumination. And though the stained glass in our front door had been shattered by a bomb blast during the Blitz (it was replaced by an unpleasant, bobbly white glass), its colors, intensified by nostalgia perhaps, still remained preternaturally vivid in my memory – especially now that Uncle Abe had explained its secret to me.[55]

Though Abe had expended much effort on the development of luminous paints, and later on phosphors for cathode-ray tubes, his central interest, like Dave’s, was in the challenge of illumination. The hope he had nourished, from early on, was that it might be possible to develop a form of cold light as efficient, as pleasant, as tractable, as hot light. Thus while Uncle Tungsten’s thoughts were fixed on incandescence, it was clear to Uncle Abe from the start that no really powerful cold light could be made without electricity, and that electroluminescence would have to be the key. That rarefied gases and vapors glowed when electrically charged had been known since the seventeenth century, when it was observed that the mercury in a barometer could become electrified by friction against the glass, and this would set up a beautiful bluish glow in the rarefied mercury vapor in the near vacuum above.[56]

Using the powerful discharges from the induction coils invented in the 1850^s, it was found that a long column of mercury vapor could be set glowing (Alexandre-Edmond Becquerel suggested, early on, that coating the discharge tube with a fluorescent substance might make it more suitable for illumination). But when mercury-vapor lamps were introduced, for special purposes, in 1901, they were dangerous and unreliable, and their light – in the absence of a fluorescent coating – was too blue to allow domestic use. Attempts to coat such tubes with fluorescent powders before the First World War collapsed before a multitude of problems. Other gases and vapors, meanwhile, were being tried: carbon dioxide gave a white light, argon a bluish light, helium a yellow light, and neon, of course, a crimson light. Neon tubes for advertising became common in London by the 1920^s, but it was only in the late 1930^s that fluorescent tubes (using a mixture of mercury vapor with an inert gas) started to become a commercial possibility, a development in which Abe played a considerable part.

Uncle Dave, to show he was not bigoted, had a fluorescent light installed in his factory, and the two brothers, who had seen the tussle of gas and electricity in their youth, would sometimes argue about the respective merits and drawbacks of incandescent and fluorescent bulbs. Abe would say that filament bulbs would go the way of the gas mantle, Dave that fluorescents would always be bulky, never a match for the ease and cheapness of bulbs. (Both would have been surprised to find, fifty years later, that while fluorescents had evolved in all sorts of ways, filament bulbs remained as popular as ever, and that they coexisted in a comfortable and fraternal relationship.)

The more Uncle Abe showed me, the more mysterious the whole thing became. I understood a certain amount about light: that colors were how we saw different frequencies or wave-lengths; and that the color of objects came from the way they absorbed or transmitted light, obstructing some frequencies, letting others through. I understood that black substances absorbed all the light, letting nothing through; and that with metals and mirrors it was the opposite – the wave front of light particles, as I imagined it, hit the mirror like a rubber ball and was reflected in a sort of instant bounce.

But none of these notions was helpful when one came to the phenomena of fluorescence and phosphorescence, for here one could shine an invisible light, a ‘black’ light, on something and it would glow white or red or green or yellow, emitting a light of its own, a frequency of light not present in the illuminant.

And then there was the question of delay. The action of light normally seemed instantaneous. But with phosphorescence, the energy of sunlight, seemingly, was captured, stored, transformed into energy of a different frequency, and then emitted in a slow dribble, over hours (there were similar delays, Uncle Abe told me, with fluorescence, though these were far shorter, just fractions of a second). How was this possible?