Chapter 22
Steam wafted up from the bubbling cauldron, bringing with it the acrid scent of burning coal.
After the chill of the brisk autumn breeze stirring up whitecaps on the river journey down to Woolwich, Wrexford found it hellishly hot within the cavernous foundry of the Royal Arsenal and quickly removed his hat and overcoat.
Spotting a workman rolling a cart of coke—a high carbon fuel created by heating coal at a high temperature to remove its impurities—toward one of the side chambers, the earl waved him over. “Can you tell me where Mr. Stoneham is conducting his research?”
“Follow me, sir,” came the reply. “Quickly, please. This coke is for him, and he gets quite impatient if he’s kept waiting.”
He followed without comment, wondering why Congreve, who had access to the British military’s Royal Arsenal and research laboratories, would feel the need to hire an outside expert on metallurgy.
Given that cannons and a range of other advanced weapons were produced within the walled complex, the resident engineers and chemists were among the finest scientific minds in the country.
Stoneham was very good … but it puzzled him as to how his fellow chemist had caught the eye of Congreve.
Yet another mystery.
Which was why he had accepted the invitation to make the long journey downriver to Woolwich.
“Ah, Wrexford!” Stoneham stepped back from a massive iron cauldron and grabbed up a towel to blot the sweat from his brow.
“Just in time!” Without further preamble, he stepped around another cart loaded with pig iron, handed the earl a thick leather apron and gloves, then launched into a detailed technical explanation of the current work in progress.
“This batch of pig iron was made by layering iron ore, coke, and limestone into a blast furnace and heating to one of the higher temperatures possible. Once the slag of silica and other impurities rose to the surface, we reheated it and did a second skimming of the impurities. The we took it to the furnace with pure oxygen and a flux of limestone to reduce the carbon level—”
“What level are you trying to achieve?” asked Wrexford.
“Ah, that’s a key question. As you know, .03 percent is standard for steel, as it is a good balance between strength and malleability. But refining it to a slightly lower percentage could make a big difference in quality of our final printed banknote.”
The earl took a moment to ponder what he had just heard. “I’ve worked with steel, but my expertise is more with the nuances of iron ore and different types of iron. I would have thought that the metallurgists here at the Arsenal would provide better advice than I can offer.”
“They’re not eager to share their knowledge. To be frank, they resent that Congreve brought me in to work on such a prestigious project. This is a private endeavor, and though the government is allowing him to use the facilities, it is not part of his government duties.”
Stoneham quirked a humorless smile. “He is paying us very handsomely, so I suppose I can understand their point. I’m very good at what I do, but most people will assume—perhaps rightly—that I got the appointment because of my connections to the Bank of England.”
Wrexford made a quick mental review of the bank’s board of governors and failed to find—
“My older sister is Bertram Ainsley’s wife,” added Stoneham. “She has always looked out for me. And as her marriage has given her entrée to the highest circles of Society, she has, on occasion, been able to advance my career through her connections.”
He smoothed at the crease in his leather apron. “I sought no such favorable treatment, but when this offer came …” His tone had turned a touch defensive. “I decided to accept because it was an interesting challenge, and one which I felt suited my skills.”
“No matter how you came to obtain the position, I agree that you’re eminently qualified to hold it. So I’m happy to give what advice I can,” responded the earl. “However, I’m still in the dark as to what this printing process of sider … sider-something entails.”
“Siderography, milord,” said Stoneham. “The name derives from sidiros, the Greek word for iron.”
The earl nodded politely. Having studied ancient Greek for more years than he cared to count, he knew exactly where the term had come from but decided that appearing out of his depth in the field of printing processes could work to his advantage.
“Whatever it is called,” he said, “the concept is also Greek to me.”
“In a nutshell, the process of siderography involves three steps,” replied Stoneham.
“One first creates an intaglio design on a soft steel die, then one transfers the design onto a roller die, which transforms it into a relief impression. That roller die is then used to recreate the intaglio image on a printing plate.”
“Why the devil would one go through all that trouble?” demanded Wrexford.
“There are a great many technical answers to that,” replied his colleague.
“Steel plates last longer than copper plates, so the quality of the image doesn’t deteriorate, making the technical challenges harder for forgers.
Also, the master roller die is capable of making many identical printing plates, so it can save a great deal of time and labor in the actual printing of banknotes. ”
Stoneham pursed his lips. “Another benefit of the ability to make many identical plates is the fact that they can then be shared with regional banks, making it possible to create a national currency. The government feels that part of the counterfeiting problem in Britain stems from the fact that regional banks are allowed to issue their own currencies. That muddies the waters, so to speak.”
“In other words,” mused Wrexford, “if people are having to handle a number of different banknote designs, it makes it harder for them to spot a counterfeit one.”
“Precisely.”
The earl thought for a moment. “I understand the two points you just made, but getting back to siderography, I am still a little lost concerning the terms intaglio and relief.” That was not precisely true.
Ainsley’s explanation during the demonstration at the Bank of England had been clear enough, but it did no harm to make sure he understood everything correctly.
“My wife is an artist and would likely know exactly what you mean, but I require a more detailed explanation.”
“The difference between them is actually simple,” answered Stoneham.
“Intaglio refers to the technique of cutting a design into a printing surface, like copper or steel. Ink is rolled over the surface and then wiped away, leaving only the pigment that has been forced into the indentations made by the cutting tool. Paper is then placed over the plate and it’s run through a press that exerts great pressure and forces the paper into the indentations. ”
“So, an engraving or an etching is an example of intaglio,” observed Wrexford.
“Correct, milord,” responded Stoneham. “Relief printing is based on the exact opposite principle. The ink rolled over a relief printing plate stays on the surface, and that is what makes the printed image—the cut-away areas appear as the same color of the paper. A good example of relief printing is woodcuts—or the metal type used for printing books and newspapers.”
Wrexford had found the discussion illuminating.
It was always enjoyable to learn new things.
And yet his basic question was still not answered.
He was about to voice it when Stoneham crouched down to make an adjustment to the firebox beneath the cauldron of molten steel and then gestured for the earl to follow him to a work counter running along the far wall.
A sheaf of technical drawings was spread out across its surface, and dotted in between the papers were several metal objects.
“No doubt, your next inquiry was going to be about the middle step of siderography—”
“Yes, the roller die,” voiced the earl. “How does it come into play?” A less polite way of wording it would have been to demand—why in the name of Hades is it needed?
Stoneham was no longer looking quite so smug as before.
He picked up one of the metal objects, which was shaped like a wheel.
“As I alluded to before, the blank roller die rolls over the original intaglio design on a special machine that exerts great pressure. And because it’s made of a soft steel, it creates an exact copy of the intaglio design—but it’s now in relief. ”
“The printing area is raised, rather than carved into the metal.”
A nod. “Another great advantage is that we can combine several intaglio dies—adding various elements like guilloches—and lock them together before making the roller die. All those intricacies in the final printed banknote will again make it very difficult for forgers to copy.”
Stoneham released a sigh. “Here comes the complicated part. We then need to harden the top layer of the die by adding carbon content, so that it can withstand the pressure needed to recreate the intaglio design on a special steel printing plate. But it must be done without altering the minute details of the design. For we need the die to recreate the original intaglio plate many times over, with each of them being exactly the same as the original.”
Wrexford waited for his colleague to go on.
The low-pitched gurgle of the molten metal—sounding to Wrexford’s ears like the rumble of a sleeping dragon as it floated through the plumes of steam—seemed to amplify the leaden silence.
“And pray tell, how exactly do you do that?” he finally asked.
“Through heating and then quenching the die in water or oil.” Stoneham put down the sample roller die with an audible thunk. “However, we have yet to figure out the exact temperature and timing to do the process correctly.”
“Lady Wrexford! It’s always a pleasure to see you here.”
“Thank you for rescheduling my lesson on such short notice, Harry,” replied Charlotte with a jaunty flourish of her fencing foil. “I am exceedingly grateful.”