Age of Invention: Just Kiln Time

The Quest for Pale Ale, Part I

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I had a great question in response to the last post on how coal usage first expanded in late-sixteenth-century England.

If London’s brewers had made the switch to burning coal in the 1580s, heating up water via the walls of the flue, and so preventing the brew being tainted by coal’s sulphurous fumes — a technique known as the holzer-sparungs kunst, or wood-saving art — how did this fit with another popular story, of how pale ales had arisen from brewers switching to coal much later, in the 1640s?

The answer is to do with how the heat was being used, involving two very different processes. The process in the 1580s was about using coal in the brewing itself, to boil the water ready for the malt to be mixed in. What changed in the 1640s, however, was not to do with brewing, but with the preparation of the crucial raw ingredient, the malt — grain soaked in water, allowing it to begin germinating, at which point it was dried to prevent it growing any further, and then lightly milled. Malt was a substance that brewers typically bought ready-made, so what changed was really nothing to do with brewers at all, but with with their suppliers, the maltsters.

[I thought this would be a quick and easy post to write — one I could get down in a matter of just a day, and no more than a few hundred words long. Seven weeks later, however, here we are, because it turns out that the road to mass-produced pale ale was a lot longer, more winding, and more interesting than expected, but with nobody ever having written it all up before.]

To appreciate what maltsters were trying to achieve, we first need to understand why it mattered for ale to be pale. It was essentially a sign that the malt used in making it had been dried well, and with minimal smoke from whatever fuel had been used. The smokier a malt, the worse the ale, taking on a dull, reddish hue said to “hurt and annoy the head of him that is not used thereto, because of the smoke.”¹ As a physician put it in 1691, beer or ale with “a high martial colour … proves injurious to the drinkers; it sends fumes and cloudy vapours in to the crown, hurts the eyes, heats the blood, and a great friend to the stone and gravel” — that is, to kidney stones.²

There were already some longstanding ways to get around this. If malt could be dried in a hot sun, for example, as has probably been done since ale was first brewed thousands of years ago, then it was entirely smoke-free and pale. In especially windy places too, the warm summer air could be caught and directed to dry out the malt. But such conditions are relatively rare in the wet and rainy northwest of Europe, so to produce malt in any quantity, and all year round, it would have to be dried in a kiln, and by burning something — which meant there was the risk of it being infected by smoke.

The kiln worked as follows. Once the germinating grain had been drained of its excess water, the maltster spread it evenly across a haircloth, which was placed on a mat woven of straw, wicker, or thin wooden splints. The mat was designed to allow hot air to pass up through the gaps from below, rising up through the sodden grain to carry all its moisture away. This porous mat — called the malt kiln’s “bedding”, or floor — was then placed over the top of a widening furnace flue, with the fire lit at the narrowest point some distance below.

A traditional malt kiln with an open hearth

Given the fire was placed directly beneath the grain, one of the maltster’s most important skills was their ability to manipulate heat. Unlike brewers, who merely piled on the fuel to bring liquids up to the point of boiling as quickly as possible, the maltster needed to get enough hot air through the mat and quickly enough to stop the grain from germinating any further, but not so much heat that the malt began to roast, destroying the all-important enzymes needed to convert starch into sugars when brewing. As one seventeenth-century writer put it, “too rash and hasty a fire scorches and burns it, which is called amongst maltsters ‘firefanged’; and such malt is good for little or no purpose”.³

Too large a fire could also be dangerous given it was not far beneath the highly combustible material of the kiln floor. Unattended malt kilns were a major cause of house fires, and so maltsters — usually women — were supposed to sing while they stoked the flames. As one old proverb put it, “Take heed to the kell, sing out as a bell”, and another “Let Gillet be singing, it does very well, to keep her from sleeping and burning the kell”. (Gillet is a name contracted from Aegidia; in seventeenth-century works you’ll often see “Jack and Gillet” to mean the ordinary man and woman, rather than “Jack and Jill”.)⁴

So malt-drying, unlike brewing, required the heat to be sustained over the course of days, and above all gently. As one well-known proverb put it, “soft fire makes sweet malt”.⁵ But this was easier said than done. In stoking the fire and turning the malt, the maltster had to account for the humidity and temperature of the air and of the sodden grain, the thickness and evenness with which the grain had been laid on the haircloth, and the difficulty of getting a fire to give out a steady heat without the use of thermometers or hygrometers. Drying the malt both gradually and evenly took great experience and skill. As one writer put it, “to keep a temperate and true fire is the only Art of a most skilful maltster”.⁶

And the art could be all the harder depending on the fuel they used. Wood could be used to give out a fairly steady fire, but it was far too smoky: “when at any time drink is ill-tasted, they say straight [away], ‘it was made of wood-dried malt’”. Or as another writer it, “the unpleasantness … I leave to the judgement of them that have travelled in Yorkshire, where, for the most part, is nothing but wood-dried malt only.”⁷ Much better was wood that had been baked into charcoal, freeing it of its smoke-producing impurities. But charcoal was much more expensive, only really affordable for the home-made malts and ales of the country houses of the rich.

Cheaper than wood were options like furze, gorse, or bracken, but these tended to be smoky too, so the most widely-used fuel was straw. As one writer put it in the 1620s, “the best and most principal fuel for the kilns (both for sweetness, gentle heat, and perfect drying) is either good wheat-straw, rye-straw, barley-straw, or oaten-straw; and of these the wheat-straw is the best, because it is most substantial, longest-lasting, makes the sharpest fire, and yields the least flame.”⁸ The proverbs agreed: “Some dry with straw, and some dry with wood. Wood asks more charge, and yet nothing so good.” Straw, however, was difficult to maintain at a constant temperature, demanding the most of the maltster’s art.

Although straw was certainly the cheapest and most widely-available fuel, there were a few places blessed with a much cleaner and steadier one, such as the coal mined in Pembrokeshire in southern Wales. By 1600, by which time it must have been used in drying malt for centuries, this Welsh coal was described as being so smokeless as to dry even cloth “without stain or blemish”, and thus also “a most proved good drier of malt, therein passing wood, ferns and straw”.⁹ Even as late as the 1750s it was said to make a “more true and complete malt … than any other fuel, because its fire gives both a gentle and certain heat, whereby the corns are in all their parts gradually dried”. The fickler fire of straw could only come near it when handled by maltsters of uncommon skill, and was smokier to boot.

But Welsh coal was an especially pure, hard, and rock-like coal, known as anthracite, and relatively rare. The more commonly-found coals of Britain were full of smoke-producing impurities, and so despite being the cheapest fuel of all, were utterly unusable for drying malt. As one writer put it plainly in the 1620s, smoky fuels like coal were “not by any means to be used under kilns”.¹⁰

If only maltsters could take even these more sulphurous and smokier coals, and find a way to prevent the smoke from touching the malt, then they would have a fuel that burned much more regularly and evenly than straw, and which was much cheaper too. Vast quantities of high-quality straw, burnt to mere ash in the malt kilns, would instead be freed up to feed livestock in winter, and so be processed by their guts into fertilising manure. If they could find a way to shift to burning cheap and sooty coals, maltsters would not only save their own costs, but make meat and grain more plentiful for everyone else as well.

Inventing the Smokeless Kiln

There was an obvious way to achieve this, which was by simply separating the fire’s from the malt, so that it was heated indirectly — the exact same principle as the holzersparungs kunst, discussed last time, which in the 1580s so revolutionised London brewing. As early as 1573, for example, the English spy William Herle sent his master, the secretary of state William Cecil, a drawing of a malt kiln he had seen in Holland with a note that “the chief effect hereof is that it is without all danger of fire, it will dispatch a great deal quickly with small fuel and attendance, and lastly seacoal [that is, cheap, sooty Newcastle coal] is as sweet a fuel for it as any straw.”¹¹

Herle’s drawing seems to have gone missing, unfortunately, but in any case nothing seems to have come of it. Seven years later the mathematician John Blagrave petitioned for a patent for a kiln “to dry malt, beans, peas, starch, biscuit, dyers’ wool, hops, or such like without damages of firing or smoke”, with the fire “to be made but morning and evening without any more attendance to be given in respect of the fire”. Blagrave added that it might even be used to heat rooms that had no chimneys, and to dry gunpowder too.¹² But his petition came to nothing, and another sixteen years later, in 1596, the son of a successful London brewer, Hugh Plat, published a short tract describing yet another version, calling it “a secret both new and profitable for our English maltsters, whereof as yet there is not so much any model extant”. Rather than laying the sodden grain over a porous kiln floor made of wicker or wood, Plat suggested placing it upon an impermeable thin sheet of lead. The fire thus simply heated the lead and then gently sort of toasted the grain, rather than smoke-drying it, allowing any fuel to be used. Plat even suggested heating the lead with the steam from brewers’ boilers, so as to recycle their waste heat.¹³

Hugh Plat’s malt kiln, based on his description. He mentions “four vents within a foot of the floor, made in equal distance each from the other, both to draw up the heat and steam of the fire, as also to convey the smoke by small leaden pipes into some wooden trunk or tunnel of brick or plaster.” I’ve interpreted this as flues to help draw the smoke once it passes the leaden floor.

Despite being published, however, Plat’s indirectly-heated malt kiln does not seem to have taken off. In 1613, almost another two decades later, an entrepreneur named John Rovenzon, or Robinson, published some details of a patent he had acquired for smelting iron with coal. Rovenzon’s process involved indirectly pre-drying the iron furnace using a coal-burning stove, and this stove, made of iron, had “funnels or passages to vent the smoke”. Thanks to this, he suggested, it might also be applied to using sooty Newcastle coal to dry malt (or starch, or hops, or saffron) “exceeding sweet and fair without scent, taint or touch of the fuel or any smoke proceeding therefrom”.¹⁴ Rovenzon doesn’t seem to have done anything with this hint, and I can’t find any other details of how it looked. His iron project amounted to nothing, and the only other record I can find of him is from the very same year as one of the three patentees for the colonisation of the South American coastline between the rivers Amazon and Essequibo — a stretch of land including Suriname, French Guiana, the Brazilian state of Amapá, and some of modern-day Guyana — which also miserably failed.¹⁵

Yet there are a few hints of the principle being put into practice, though without any indication of who was responsible. In a book probably written around the same time, but published a decade later,¹⁶ is a note about some kind of smokeless malt kiln becoming popular: “there is a kiln now of general use in this kingdom, which is called a French Kiln … ever safe and secure from fire, and whether the maltster wake or sleep … and in these kilns may be burnt any kind of fuel whatsoever, and neither shall the smoke offend or breed ill taste in the malt, nor yet discolour it, as many times it does in open kilns, where the malt is as it were covered all over and even parboiled in smoke”.¹⁷

What’s frustrating here is that the French Kiln was apparently too popular to even bother describing: “of the form or model whereof I will not here stand to entreat, because they are now so generally frequent among us, that not a mason or carpenter in the whole Kingdom but can build the same, so that to use more words thereof were tediousness to little purpose.” Argh! Will nobody think of the historians?

But the author — the agricultural writer Gervase Markham — does give us hints of how it worked. In another volume he says that whereas English kilns are typically “composed of wood, lath and clay, and therefore subject to some danger of fire”, the French kilns were “of brick, lime, and sand, and therefore without all peril”.¹⁸ The floor or bedding of the French kilns was still, however, of porous wicker or wood — which suggests that if the smoke was not affecting the sodden grain upon it, then it was not just a matter of better materials, but of design. Although I don’t think it removed the smoke entirely — for reasons that will become clear — it sounds as though the French kiln involved installing a series of brick baffles between the flame and the kiln floor, so that by the time the smoke reached it, it had lost much of its soot and was mostly just hot air.

Did the “French Kiln” work something like this?

We may never know for sure. I painstakingly checked every version of Markham’s book, which went through many editions over the course of decades, but his text on malt kilns was never updated. Nor can I find any other reference to it. But he does at least give us the description of another kiln he’d seen used in the West Country, which likewise helped to reduce the smoke and may have worked similarly. Although it was too small to be applied to industrial-scale malting — Markham described it as having a “profitable quaintness” — it involved opening a vent from an ordinary kitchen fire so that some of the heat instead went down a tunnel to a small malt kiln. With the vent competing with the kitchen chimney’s ordinary flue, and with plenty of soot being lost in the tunnel along the way, it seems to have made for a relatively smokeless malt.¹⁹

Yet neither the French nor West Country malt kilns seem to have entirely solved the problem of smoke. In 1622 the general idea was mentioned in a book on trade as an illustrative, but hypothetical, example of a hugely beneficial invention: “If a kiln for the drying of malt for all the Kingdom over were invented to be done with pit coal, better cheap than with wood fire, and more pleasing, without the scent of smoke”, argued the author, then if granted a patent monopoly, it wouldn’t be considered unjust — an argument that just a year later was put to the test.²⁰

Burning Ambition

In 1623, a partnership was formed to promote and patent a newly-invented smokeless malt kiln. The partners were the governor of Pendennis Castle, a Cornish gentleman named Sir Nicholas Halse of Fentongollan; a Cambridgeshire knight named Sir Henry Mallory; and one John Shotbolt, alias Battalion, of Ardeley in Hertfordshire.²¹ Although Halse was the chief mover of the project — the entrepreneur — the kiln’s actual inventor, I suspect, was Shotbolt, who a few years earlier had invented an instrument to repair highways;²² was leading the drainage of the peaty Sedgemoor in Somerset;²³ and, most strikingly of all, had approached king James I about some kind of stove for drying saltpetre, the key ingredient in gunpowder.²⁴

Over a decade later, Shotbolt’s saltpetre-drying method was to get the financial and political backing of a Dutch-born gentleman, Sir Philiberto Vernatti, a knight of both Venice and England, who bought a baronetcy by funding the colonisation of Nova Scotia, set up glassworks in Scotland, led a consortium of Dutch investors in the drainage of the English Fens, and was to fund new attempts — after Rovenzon’s failure — at smelting iron with coal. Vernatti and Shotbolt petitioned the king in 1634 to allow them to take over the perpetual patent monopoly on saltpetre production, arguing that the current patentee had failed to keep to the Crown’s terms.²⁵ And although this seems to have failed, soon afterwards Vernatti patented the saltpetre-drying stove in the Dutch Republic.²⁶

What’s so interesting about Shotbolt’s saltpetre-drying stove is that the heat had to be applied gently, and that the risk of hot soot coming into contact with the saltpetre might potentially have been explosive. So if his stove could apply a gentle, smokeless heat to drying saltpetre, it could almost certainly be applied to drying mere malt. Indeed, what’s striking here is that Shotbolt’s malt kiln also suddenly re-emerged, also after about a decade’s silence, in 1634.

According to the inventors themselves, the reason for the decade’s delay was simple. In 1625, king James I had instructed his officials to draw up the partnership’s malt-drying patent, granting it to Sir Nicholas Halse for the unusually long term of 31 years — far longer than the 14 years permitted to patents for new inventions under the Statute of Monopolies, passed just two years before. The idea seems to have been similar to the patent then in force for making glass with coal instead of wood. In order to preserve wood and timber, seen as a matter of strategic necessity, the making of glass with coal was not just protected as a newly-invented process, but the older use of wood was banned as well, giving its patentees a full monopoly on English glass-making. Halse seems to have reasoned that if a special exception could be made for a small industry like glass-making, then it could also be made for a much larger one like drying malt. But before the patent could receive the king’s seal, and so become official, the king died.²⁷

With the court in upheaval, Halse may have lacked the connections to apply for the patent again, though I suspect that the setback simply allowed Shotbolt to get distracted. Just a few months after the king’s death, both he and their other partner, Sir Henry Mallory, were to receive a patent to search for gold, silver, and copper mines in various counties. And a year after that, Shotbolt was complaining that delays to his drainage works at Sedgemoor meant he now faced financial ruin.²⁸ What happened in the intervening period is unclear, but in 1634, having now acquired the backing of Philiberto Vernatti for his saltpetre-drying, Shotbolt resurrected the partnership with Halse and tried to promote the malt-drying invention again — this time with Vernatti’s help as well.²⁹

What they now proposed was even more ambitious than before. Playing on Charles I’s constant need for cash, the partners proposed that the invention form the basis of a powerful new corporation, the Society of Maltsters, of which Vernatti would be the first master, with Halse and Shotbolt as its wardens, and for which they had found 92 alleged maltsters to sign their names in support.

There were several advantages to incorporation. One of them was that when the restrictive Statute of Monopolies had made its way through Parliament a decade before, various guilds, universities, towns and cities — all self-governing corporations — had worried that the new law might undermine the patents and charters that granted their own members certain exclusive rights. They had managed to get a clause inserted in the bill to exempt all corporations from the restrictions it imposed, and so created a loophole: that if an inventor could get a patent in the name of a new corporation, rather than just as an individual, then his monopoly would not be limited to just 14 years, but could be perpetual.

Moreover, by presenting a business partnership as a new and necessary guild, officially regulating and speaking for an entire profession, then they could also force the entire industry to use the invention. As Vernatti, Halse and Shotbolt put it, their new Society of Maltsters would bring about a “reformation” of abuses, as well as raising the standards of the industry by ensuring the “sweet, neat and wholesome drying of malt … without any touch of smoke”. Nobody would be allowed to be a maltster unless they became a member of the corporation, and nobody could become a member of the corporation without both using the invention and paying a membership fee — which would, in effect, be the invention’s licensing fee. And to sweeten the deal for the king, they proposed that the corporation pay him a share of those fees. So the corporation would, in effect, raise a major new tax on malt.

Although another such scheme had recently been approved for monopolising soap-making, for some reason the partnership’s proposals were rejected. Perhaps the government worried that malt-making was simply too vast an industry to regulate in this way, and that it would prove too unpopular. By Halse’s own estimation there were some 40,000 practising maltsters in the country,³⁰ which would have accounted for almost 1% of the entire population, and an even higher proportion of its working adults. Or they may have just been beaten to the punch by someone better connected.

A brewer and naval captain named James Duppa, whose younger brother was the king’s chaplain and tutor to the royal princes, had already been petitioning for a an alternative means of effectively taxing malt, and a few years later was given the go-ahead by a royal commission to suppress the “unnecessary and unlimited number of common maltsters” — common in that they made malt for the public rather than for their own use at home — and to prevent all innkeepers and alehouse-keepers from brewing their own ale or beer.

Although there was no mention of any new invention, Duppa’s scheme established an even more direct licensing regime to cover all malt and beer made for public consumption, forcing maltsters and brewers to pay up or else be forced out of business. Despite being put into operation, Duppa’s new, nation-wide excise tax proved short-lived. With maltsters dissuaded from supplying the market, and with malt in even shorter supply thanks to a poor grain harvest a few years later, the rising price of malt and the resulting outcry from the brewers forced the government to water down the terms of Duppa’s licensing regime. And with London also being exempted from the scheme because of its ancient civic privileges, the government raised hardly any cash while managing to foment a great deal of discontent. It was one of the many, many straws to be laid on the camel’s back, which led just a few years later to civil war — a war that Parliament won, ironically, because in 1643 it instituted a proper, no-exceptions excise tax on making ale and beer.³¹

In the meantime, however, in 1635 Sir Nicholas Halse and his partners had to console themselves with the grant of an ordinary, 14-year monopoly on the use of their invention. Halse didn’t get long to enjoy it, as he died the following year, but the people who got his share were soon trying to stamp out the competition, the trouble being that a few other people had already patented a very similar-sounding idea. In 1634, while Halse was still petitioning for the creation of a maltsters’ corporation, a patent for another smokeless malt-drying kiln had been granted to an appropriately-named clerk, Nicholas Page. And a few months after that, yet another was granted to the disappointed heirs of Cornelis Drebbel, who had apparently made himself penniless in the process of inventing a smokeless malt-drying stove.³²

Unfortunately, we don’t know how exactly these malt-drying devices differed, yet there are some tantalising hints. For details about the kiln Halse patented, and which Shotbolt likely invented, we have to thank a physician, Dr Edward May, who at around the same time was promoting his invention of a hanging “pendant furnace” to use on ships. May’s device was mostly made of iron, with the idea being that it would replace the huge weight of brick and mortar — about seven tons — required for the ship’s oven, usually located in its bow. That weight, he noted, “makes the forepart of the ship draw deep in the water, and so slugs the ships”, slowing it down, and so the idea was that that the pendant stove, weighing less than half a ton, could be hung from iron bars, staying ever upright even as the ship pitched and rolled, as well as potentially being carted around the deck on wheels. May’s invention was apparently recommended for trials, after which all mentions cease. It wasn’t until over a hundred years later that iron stoves — non-hanging ones — were introduced as standard on new naval ships. But May did, helpfully, mentio a few ways in which his device differed from the Halse/Shotbolt one.

For a start, he noted that Halse’s partners claimed “only unto the standing and fixed furnaces and ovens” — that is, of a permanent structure largely of brick, rather than a portable iron stove. And, he noted, he had made a licensed addition to his own design based on how Shotbolt’s worked: “upon the consideration of the furnaces of Sir Nicholas Halse, Doctor May was put in mind to add unto his pendant furnaces the stove roaster which himself had seen often times in Germany and Helvetia [Switzerland], and the further parts of Lorraine.”³³ From this, and some mentions elsewhere of it being reliant on iron,³⁴ my current best guess is that the Shotbolt/Halse device separated the smoke from the malt entirely, but that this involved the smoke being walled off with iron plates to conduct and retain the heat.

Might Shotbolt’s malt kiln have looked something like this? I suspect he was more sparing with the iron, but without further details I don’t know where he’d have placed it.

As for Page’s competing kiln, the Halse partnership argued that he had simply stolen their idea. Halse had apparently shared a lot of drawings and descriptions around — it would be wonderful if one of these turned up one day — and Page had, they alleged, simply rushed to patent it first.³⁵ After a short investigation the government agreed, and Page’s grant was suppressed. But he wasn’t really given the chance to defend himself.

The problem Page faced was that Halse’s investors had included one William Howard, who it appears was one of the Howards — a family whose members included the earls of Arundel, Berkshire, and Suffolk. Indeed, I suspect that this William was the youngest son of the earl of Arundel — the most powerful of the three earls, as Lord Marshal, Lord High Constable of England, and a member of the king’s privy council. If so, this William was about to be given the title Lord Stafford, and in a few years raised to a Viscount. As a friend of their other competitors put it, “now my Lord Arundel pretends to have the same skill and likewise has a patent for it”.³⁶ And very soon, Arundel’s cousin, the earl of Berkshire, was to emerge as the Halse partnership’s new leader.³⁷

So Page faced formidable foes. When the Howards petitioned the king to ask for Page’s patent to be withdrawn, the king’s legal advisers pointed out that while this was in theory perfectly doable — he could grant and retract a patent at will — determining who was actually first in the invention could only properly be decided by a court of law. Page would likely have expected at least a trial. But in May 1637 the Howards instead persuaded the king to refer the question to a committee of courtiers, most of whom seem to have been Howard clients.³⁸ “Summer is”, the Earl of Berkshire argued, “the time to build kilns, and winter to use them”, and the potential benefits to the country were too important to allow any delay.³⁹ Poor Page was left without any time to prepare, imploring the king, to no avail, that he could not, with just a few days’ notice, “suddenly be provided of commissioners, and draw up interrogatories, and bring in witnesses”, his lawyers informing him that it would cost him far more than a simple trial as well.⁴⁰ He never stood a chance.

I suspect that Page was not a an intellectual property thief at all, and had actually patented a different kind of malt kiln. At some point he petitioned to continue using the invention, pointing out that it didn’t use iron plates like Shotbolt’s, and promising to pay more of his profits to the Crown.⁴¹ He may, of course, have just been making this up, and unless new evidence turns up we’ll probably never know for sure. But what we do know is that the other competitor the Howards wanted to crush — the smokeless malt kiln patented by the heirs of Cornelis Drebbel — was actually a major technological breakthrough.

The Government of Fire

A Dutch engraver and alchemist, Cornelis Drebbel is not a widely-recognised name today. But he was one of the most influential scientists of the early seventeenth century, and easily Europe’s most famous inventor. Considered a maverick even at the time, he was the da Vinci of his age, but significantly better, as he actually put his most outlandish designs into practice. As one admiring scientist put it in 1649, when comparing Drebbel to the now much more celebrated Descartes, the best natural philosopher was not only one who understood “nature’s works”, but “knows how to rule them in order to the procurement of good to Mankind … Till Monsieur des Cartes has proved himself a philosopher in this sense, I shall prefer Cornelius Drebbel before him, though he understood no Latin — one that has done more though said less.”⁴²

One of Drebbel’s core insights about the world was that he could exploit changes in temperature and atmospheric pressure to produce motion. By harnessing the perpetual motion of the universe, but in miniature, he caused a sensation throughout the courts of Europe when he unveiled a clock that would never stop. Showing the time, day, months, and years, the signs of the zodiac, the phases of the moon, and seemingly — though not actually — the ebb and flow of the tides, its internal springs were rewound by the expansion of some trapped mercury pushing upon a piston every time it got warmer during the day. (I hypothesised this as a plausible explanation in a post I wrote three years ago, and it’s how I had it shown in a 3D animated reconstruction that you can play around with here, but in the process of researching this piece I accidentally stumbled across some actual evidence to confirm it!)⁴³ In exactly the same way, he amused the court of the English king by applying the principle to getting statues to sing or play music whenever the sun shone on them.

But he also had more useful applications in mind. At some point in the 1610s he was not just exploiting changes in atmospheric pressure, but measuring them too, using this to predict storms. Drebbel’s barometer became known in Dutch as the donderglas, or the thunder-glass, and in England as the weather-glass or kalender-glass (drawing up a calendar in the seventeenth century was not just a matter of listing dates for holidays, but of using astrology to predict the weather for the days ahead). And because the countervailing effects of changes to temperature were not to be separated and isolated until decades later, Drebbel’s device could also double as a thermometer — one known as the “Dutch” or “Drebbelian” thermometer, as opposed to the near-identical “Italian” one invented in the 1610s by the professor of medicine at Padua, Santorio Santorio.

By using his device as a thermometer, Drebbel was to go beyond just exploiting or measuring temperature, discovering a way to control it. Drebbel, as an alchemist, needed to be able to precisely control the temperature of a furnace so as to manipulate minerals and metals. Just like the chief art of the maltster, this art of the alchemist, known as pyronomia, or the regimen ignis — the governing of fire — demanded the cultivation of an exceptional sensitivity to heat, so as to judge by feel and by look the varying intensities of the flame and then do what they could to keep it at a constant level. Drebbel’s mercury thermometer immediately made this easier, but he went much further, removing the need for any art at all. By placing a cork to float atop the thermometer’s mercury, its rise and fall could then push a lever to either open or restrict the fire’s air supply, and so keep the oven at a stable heat automatically. Drebbel had invented the thermostat, allowing him to simply choose a desired temperature and let the stove do the rest.⁴⁴

Drebbel’s thermostatic stove was to be widely adopted, and became a major source of business for the husbands of his daughters, the brothers Abraham and Johannes Sibertus Kuffler, to whom he passed many of his secrets (Drebbel seems to have liked them more than he liked his own two sons). The Kufflers successfully used the invention to artificially incubate chickens, to distil seawater on ships — especially useful on long-distance voyages to the Indian Ocean — and to make portable baking ovens for armies, used by the Dutch in their successful campaigns against Spain.⁴⁵ In terms of drying malt — just one of many other applications considered by the Kufflers alongside salt-making, warming rooms, heating bath-houses, and drying saffron, hops, fruit, sweetmeats, guns, gunpowder, saltpetre, and the timbers of freshly-built homes — it sounds as though it would have worked just like a radiator heats a room today, the stove simply needing to be placed in the malt’s proximity. What really differentiated it from Shotbolt’s method, however, was that it it would have allowed maltsters to choose the heat they wanted and then to leave it be. Instead of singing to stay awake, they would have been able to go and get a good night’s rest, only returning periodically to top up the fuel. And it would have allowed even the most bumbling of maltsters, utterly inept at managing a fire, to produce an even, gentle heat, and thus a high-quality malt.

But rather than spreading in England, Drebbel’s thermostatic stoves first became popular abroad. Just as with the poor clerk Nicholas Page, it seems that Drebbel’s invention was suppressed by the powerful Howards. As a friend of the Kuffler brothers reported in 1635, the earl of Arundel’s meddling meant “that Kuffler is kept down” despite his invention being “conceived to be the better.”⁴⁶ And with the onset of England’s civil war a few years later, the brothers in any case fled to the Netherlands, where they spread Drebbel’s inventions instead.

With the competing kilns of Page and the Kufflers suppressed, the way seemed clear for Shotbolt’s invention to achieve the prize of allowing cheap coal to be burned in the making of pale malts. Even though we don’t know exactly how it worked, all the efforts that the Howards went to even without the chance of a full monopoly corporation suggest that the Shotbolt invention was widely considered valuable. In 1638, the earl of Berkshire had Halse’s patent reissued in his own name, tightening up its wording to prevent any further encroachment, and extending the uses and fuels to which it applied. And there was even, it seems, more demand than initially expected for the kilns,⁴⁷ with shares in the business still being worth something a few years later in 1640.⁴⁸ But a year after that, with the country now on the verge of civil war, the Shotbolt smokeless malt kilns were being lampooned in a satirical pamphlet as a typical example of a project doomed to fail, after which all mentions cease.⁴⁹

In 1656 the Kufflers returned to England, bringing back with them the secret to thermostatic ovens.⁵⁰ But by then there was no point in applying it to drying malt. By then, another much simpler and less capital-intensive method had been developed to use cheap coal. Instead of removing its smoke from the kiln, a way had been found to remove the smoke from the coal itself.

More on that in Part II.

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1. William Harrison, The firste volume of the chronicles of England, Scotlande, and Irelande (1577), p.96

2. Thomas Tryon, The New Art of Brewing (1691), p.51

3. Gervase Markham, Countrey Contentments (1623), p.206

4. Thomas Tusser, Fiue hundreth points of good husbandry (1573), no.60; Thomas Tusser, A hundreth good pointes of husbandry (1570), no.62

5. Markham (1623), p.206; Matthew Stevenson, The twelve months (1661); John Ray, A collection of English proverbs (1678), p.389

6. Markham (1623), p.206

7. Gervase Markham, The English husbandman (1613), p.103

8. Markham (1623), p.205

9. George Owen, ‘A History of Pembrokeshire’ [1603], in The Cambrian Register for the Year 1796, Vol II, (1799), p.105

10. Markham (1623), p.206

11. BL Lansdowne MS 18 f. 34r-v. William Herle to Lord Burghley

12. SP 12/146 f.107

13. Hugh Plat, Sundrie nevv and artificiall remedies against famine (1596)

14. John Rovenzon, A treatise of metallica. Bvt not that which was published by Mr. Simon Stvrtevant vpon his patent, which is now by order cancelled and made voyd (Thomas Thorp, 1613)

15. SP 14/141 f.65

16. The first appearance of a section on malt-making in Markham’s work appears in the second, 1623 edition of The English Huswife, appended to Countrey Contentments. But in the 1613 edition of the first part of The English husbandman (p.103) he discusses hop-drying — which was often done on a malt kiln — and the difference between the English and French kilns, while noting that “because I have hereafter more occasion to speak of the nature, fashion, and edifice of kilns in that part of this Volume where I entreat of malting, I will cease further to mention them than to say that upon a kiln is the best drying your hops”. I think it’s clear from this aside that he had already drawn up his notes or perhaps even written the manuscript for his section on malt-drying, but he then excluded it from the second part of The English husbandman published the following year, perhaps as his vision for the book’s structure had changed, and then forgot to put it in the first edition of The English Huswife published the year after that. Only when the latter went to a second edition in 1623 did he correct the oversight.

17. Markham (1623), p.200

18. Markham (1613), p.102

19. Markham (1623), p.201

20. Gerard Malynes, Lex Mercatoria (1622), p.216

21. The document is referred to in an inquiry into the priority of Halse’s patent in SP 16/323 f.31 as “articles of agreement made the 16th day of May in the 21st year [1623] of the reign of your [Charles I’s] late royal father King James of ever blessed memory made by the said Sir Nicholas Halse, Sir Henry Mallory knight, and one John Shotholt [Shotbolt] mentioning the said invention of Sir Nicholas Halse”.

22. SP 14/141 f.132, dated 23 May 1619

23. Michael Williams, The Draining of the Somerset Levels (Cambridge University Press, 1970), pp.96-101

24. SP 16/268 f.42 - in an 18th May 1634 petition by Sir Philiberto Vernatti and John Shotbolt to king Charles I they note how Shotbolt “has about a dozen years since [c.1622] been often admitted into your Majesty’s gracious father’s presence … acquainting his highness … with the great and beneficial secret of making and composing of excellent saltpetre and powder”

25. SP 16/268 f.42

26. G. Doorman, Octrooien voor Uitvindingen in de Nederlanden uit de 16e-18e Eeuw (Martinus Nijhoff, 1940), p.197, patents G 364, G 365 and G 367 (which is an amendment to G 365)

27. SP 16/323 f.31 mentions the 31-year term apparently granted by James, and that “before the patent could pass the seal the late king died, thereby the said invention was for diverse years discontinued”. SP 16/307 f.120 sets out the plan for a 31-year patent involving a dispensation from the Statute of Monopolies and a ban on any competing malt-kilns, with each new kiln to pay the Crown an annual rent of 40s per year.

28. SP 16/524 f.158

29. SP 16/323 f.31 mentions an agreement dated 7th April 1634 between Sir Nicholas Halse, Sir Philliberto Vernatti and others. This is followed by SP 16/438 f.120-1, the petitions for incorporation, which despite being calendered under 1639 cannot be, as the chief petitioner is Halse, who died in 1636. They instead must belong to May, June or July 1634, after the agreement and before, SP 16/272 f.46, dated 19 July 1634, which contains a list of answers by Vernatti to a series of objections to the incorporation.

30. SP 16/279 f.139

31. John R Krenzke, ‘“Moneys Unreceived”: Attempts to Tax the Brewing Trade in London and Its Environs before the Excise Ordinance of 1643’, Brewery History, no. 162 (2015): 2–14.

32. The patentees also complained of two other rival patents, though less applicable to malt-drying, and which may have had something to do with the exact form of the invention itself. One of these was the 1635 patent to Serjeant-Major Henry Sibthorpe for a very similar-sounding smokeless oven for cooking and baking. The other was a 1636 patent to Robert Lindsey, Esq. and John Hobart, gentleman, for a way to reduce the smoke and heat loss in boiling by brewers, dyers, chandlers, cooks, soapboilers, and hatmakers.

33. SP 16/338 f.94; SP 16/327 f.251

34. SP 16/408 f.27; see also an agreement, SP 16/372 f.69, to provide “irons and dispersers” for the invention. I’m not sure what the dispersers could be.

35. SP 16/323 f.31

36. CHECK PRECISE LOCATION: Hartlib papers, Ephemerides 1635

37. Incidentally, Shotbolt’s brother, Philip, was the Earl of Berkshire’s deputy for the patent in Hertfordshire, as mentioned in articles of agreement from May 1637: SP 16/385 f.185

38. These were Sir Richard Wynne, Sir Thomas Hatton, Sir Henry Spiller, and Laurence Whittaker Esq. All four had legal training and held various government offices, Whittaker being involved with Duppa’s malting and brewing scheme too. Wynne, who led the committee, started his career in the household of the earl of Berkshire’s father; Hatton would later be a trustee for the earl of Arundel’s son, suggesting a connection; and Spiller was definitely a client of the earl of Arundel. Although a quick search doesn’t yield much, the chances are, I think, that Whittaker had some Howard connection too.

39. SP 16/356 f.105

40. SP 16/376 f.114

41. SP 16/408 f.27

42. Hartlib papers, 7/123/1A-2B — the letter is seemingly by William Petty, himself an important scientist, inventor, economist, and statistician.

43. Hartlib papers, 45/1/16A-17B. I’d missed it because it was in Latin, but I’ve learned some new tricks for searching things over the last few years. The letter, by Henry Appelius to Samuel Hartlib, discusses the idea of perpetual motion in a general sense before giving some examples: “Drebbel had [a device] which sang as long as it was illuminated by the sun, but when a cloud passed over, it would stop: namely, the sun would release quicksilver: whose distilling droplets, caught in capsules [or receptacles / compartments] connected around the circumference of a wheel, would turn the wheel, which added motion to that instrument. The ruins of this are still seen at his son-in-law’s: as well as his Perpetual Motion, which likewise (as the same son-in-law reported to us) was driven by droplets of quicksilver gradually falling down along an oblong iron rod, which perpetually moved a small bronze [or brass] ball sitting on it.”

44. Vera Keller, ‘Re-Entangling the Thermometer: Cornelis Drebbel’s Description of His Self-Regulating Oven, the Regiment of Fire, and the Early History of Temperature’, Nuncius 28, no. 2 (1 January 2013), p.243–75

45. In John Evelyn’s diary in 1666, he reported how they had formerly been used for the Prince of Orange’s army. L. E. Harris, ‘Cornelis Drebbel : A Neglected Genius of Seventeenth Century Technology: Presidential Address’, Transactions of the Newcomen Society 31, no. 1 (January 1957), pp. 195–204. Samuel Hartlib’s notes for 1639 mention its use in the Prince of Orange’s army too, thus narrowing down both the date and the prince in question. Johannes Kuffler in 1654 told Hartlib that when Charles I had wanted to send an army to suppress Scottish religious rebels in 1639, he had asked for portable ovens for the army, but that the king never saw the invention as he was away at the time. Hartlib papers, 39/2/20A-25B. This appears to be confirmed by a document in the state papers, SP 16/414 f.267, dated 15 March 1639, which both mentions portable copper ovens being used in the Netherlands and an offer of even lighter ones made of some other material - almost certainly a reference to Kuffler’s ovens.

46. Hartlib ephemerides for 1635, part IV; confirmed also by 29/5/83A-94B, Hartlib ephemerides for 1656, Part III, where Kuffler “intimated that he had an invention for drying of malt, and that another heretofore by another form only had appropriated the invention to himself”. NB also that this kind of political intervention was very plausible. We have evidence of one of the Howards, the earl of Berkshire, for example intervening in how Dr Edward May’s pendant furnaces would be treated by the government in 1637: SP 16/348 f.20

47. SP 16/372 f.69: a partnership to supply £200-worth of iron for the kilns in 1637 was the following year raised by another £100. The agreement involved one William Davenport, a barber of London, who it appears was the patentees’ deputy for Hertfordshire.

48. SP 17/E f.81 - this is an indenture dated 8 May 1640 between the earl of Berkshire and the widow of William Davenport, the partnership’s agent for Hertfordshire.

49. Thomas Brugis, The discovery of a proiector (Richard Hearne, 1641), pp.8-10. On p.16 Brugis notes that the brewer “finds malt very dear, and never worse, which he conceives to proceed from the new kilns, and his customers cry out on him for hopping too much; whereupon he is resolved to petition his Majesty that the new project of kilns may be suppressed, and likewise the [Duppa] patent of incorporating maltsters”. This suggests that perhaps the kiln failed because it was associated with the Duppa project, though it’s unclear.

50. Negotiations to return seem to have begun in 1654 - see Hartlib papers, 39/2/20A-25B, dated 13 November 1654. In 1656, however, Hartlib was still negotiating for Kuffler to impart the secret of “that way of regiment of fire (that one need not look often unto it and may go abroad, etc) which his father-in-law Cornelis Drebbel prized at £1,500” - a huge sum of money in those days - which suggests that it was still not widely known in England. See also the draft of the agreement, Hartlib papers 27/13/7A-B, which mentions the “invention to govern an oven in such manner that the oven cannot exceed nor want the very same degree of heat as is desired, governs itself of his own accord, without help of any man”