Before I continue my pyrite experiments, I want to focus on finishing the lead production process. Doing so should allow us to recover a lot of the iron and copper that we used for making artillery rounds, since we'll be able to swap out the projectile portions of those rounds. Karsh also said he'd like to make all sorts of other things out of lead, since it's so easy to work with, but I shot down that idea. Considering how similar our biology seems to be to Earth, I'm not risking lead poisoning. Maybe the biology on this planet has an easy way to handle heavy metals, but I'd prefer to err on the side of caution.
The final step for lead production isn't that complicated, but it will require a slight change in how the city currently handles some of it's refuse, bones in particular. What we need to finish purifying our current lead according to Konkur's notes is to melt it down in shallow containers made from bone ash. That bone ash will absorb the lead oxide and leave behind a lot of other metals as long as we control the temperature of the fire. Thankfully, he left a diagram for charcoal smelters that should produce the approximate temperature for the process.
The metals recovered in this step are gold and silver, so those should be set aside for later analysis, perhaps I'll get a letter with the samples composed, along with some payment, and send it to Konkur this year. I don't know if he'll look into it or not, but I suspect he will, as long as the merchant can actually get the samples sent to him. If this step has a very low yield, then it could potentially be skipped over for processing bulk lead.
The next step for recovering the lead involves re-smelting the bone ash which is infused with lead oxides and other metal oxides like copper. It requires quite a bit of charcoal to reduce the metal oxides back into a mostly lead bullion. Finally, those bullions need to be melted again at a low temperature near the melting point of lead, leaving the other metals as a solid, and yielding a mostly pure lead metal.
So, my next course of action is to begin changing our handling of bone refuse, then to make the additions to the roasting area. One for the lead refining using the bone ash, and the other for re-smelting the lead. If this was any metal other than lead, I'd probably build them in the city, but given it involves working with lead, I don't want to potentially poison the ground water so I'm going to build it next to the ore roasting area, where I already expect those sorts of problems.
----------------------------------------
It took quite a few days to spread the word about separating out fish bones from your other refuse. It took even longer to get the practice properly handled. Ultimately, I had to settle on a recycling program style system. Individuals could purchase a small bin for their fish bones, and when the bin was filled, you could trade the bones inside for a fixed sum of money.
Getting that whole process organized ended up taking forty-three days, since I needed to hire a new goblin to handle the process, build a facility for processing the bones into bone ash, and get Zeb to have one of his stone shaping goblins spend some time each year building more bins for goblins to use for their fish bones. With that process done it means we have a steady supply of bone ash, which should have a few uses outside of our lead refining needs.
Next, I got to work on the area for the refining stage for the lead. I talked Zeb into lending me a construction team for ten days to ensure that I finished the facility in time before this winter. In those two weeks, we expanded the flat area around the roasting section to make enough room for the three new smelters, expanded the roofing, and added another underground storage area.
The tale has been illicitly lifted; should you spot it on Amazon, report the violation.
Then, I spent another twelve days building the first smelter for refining the lead. With it finished, I took another three days tinkering with the bone ash to come up with a good process to make the required containers for seeping the lead oxide into. Next, I took another ten days doing trial runs to get everything working in a reproducible way, so I could hire more goblins to handle the process long term. In those ten days, I collected quite a few small samples of the impurities from the lead, which I carefully stored.
The lead ingots from the original smelter weigh approximately ten pounds each, and after running them through this stage of the refining process, I'd receive a little bead of metal that weighed just under a twentieth of a pound. If I've done everything right, that means we're looking at about a half of a percent by weight yield of silver and/or gold.
Using conservative estimates of a 50% weight yield from the galena to our initial lead bullion combined with the five tons or so of galena we have to process, that'd yield about twenty-five pounds of these beads of silver. On one hand, it feels like a bit of a waste to do so much work for such a tiny amount of metal, but silver and gold both have pretty useful properties, and are somewhat hard to get, so it's probably worth it to continue this process.
I'll have a few samples bundled with some notes for Konkur, and hopefully he'll be able to get back to me within a year to tell me if it's considered economically viable to continue that recovery step. I took two days making a special package containing the samples, and working with one of our goblins who could write in dwarvish to have them prepare a letter to go along with the samples.
After doing those tests, I spent another ten days hiring and training three goblins to handle that process moving forward. After that, I started work on the second smelter, the one for re-forming the lead bullion with it's impurities from the bone ash. This smelter needs to get up to a high enough temperature to reduce the lead oxide again, so it needs another windmill to get the air-flow high enough to produce the temperatures necessary for a reduction reaction to occur with mixed charcoal.
----------------------------------------
Unfortunately, I had to halt construction temporarily, in order to handle our winter trade again. Though I can't say I was too upset by the interruption, considering I was expecting to potentially receive some of the crystal samples I requested. The merchant also arrived fairly early, on the ninth of the month, so I didn't end up wasting that long waiting on this side of the island.
I felt mixed emotions when I had only received a small container with three crystals in it. All three, I was told, produced heat when exposed to mana. I held one, and it did feel slightly warmer than I would have expected, so that at least made me believe it was performing as advertised.
Shasta was there to negotiate again, and also gave me a rough estimate for the number of warlords to expect at next year's auction. I was informed that eighteen had agreed to participate. Quite a few had declined, but if we included those who might still decide to participate, then we could expect up to twenty-five participants.
We unloaded the metals we traded for this year, and renegotiated new trade deals for the next year. We didn't need to trade for as many things this year, but to keep the merchant happy, I ordered enough goods to make the trip more than worth it for him. The order consisted mostly of more metals, in addition to the usual goods like clothing. Given the number of warlords who might participate in the auction next year, I traded entirely in dwarven currency for this year's trade, to ensure we have enough trade goods to give as gifts at the auction.