Iron From Scratch
Current recipe from the Rockbridge Bloomery
Serves 1 ( approx. 25 lbs. per person)
Preparation time: a few days, depending on ore and fuel supplies
Cooking time: approx. 6 hrs
As with all recipes, use this only as a springboard for your culinary creativity.
Gather and prepare:
To prepare your roasted ore, use wood or gas heat to bring the ore to a red or low orange heat. Do not let it melt! You may quench it in water, or simply let it cool before breaking it up to pea size. Pick out any obvious impurities, many of which will now show up as white, rather than red or gray.
Approx. time (hours) 0 Start preheating furnace with either a wood fire (no blast at this point, just natural draft) or with a gas burner inserted into the slag tapping arch. 0:45 Add charcoal, and start your air blast (~1200 l/min). You want to see a seriously blazing white heat through the peephole. Throughout the smelt, keep your fuel level near the top of the furnace. You may use about 80 lbs. of charcoal during this preheat. Stick a firebrick loosely in the tap arch to block it. 1:30 Add your first charge (all charges consist of 15 lbs. of charcoal, followed by 15 lbs. of ore). When there's space enough in the top of the furnace, which should be at about . 1:50 Add charge # 2. If it took much more than 20 minutes to make room for your second charge, increase your blast. 2:10 Charge #3. By now you'll probably observe molten ore dripping past the peephole.
Your heat should be continuing to increase throughout the charging sequence.
2:30 Charge #4. 2:50 Charge #5. Somewhere in here, you want to unblock your tap arch, before the hardened slag freezes the fire brick in place. If some slag dribbles out, don't worry about it, but don't encourage it at this point. 3:10 Charge #6. If this is not your first try at smelting, replace at least part of this ore charge with magnetic material and slag gleaned from your previous smelt.
By now, you should have a large bath of molten slag, and hopefully a incipient bloom of iron below the tuyere. The first ore to pass through the furnace may have been partly reduced, but did not have a chance to adhere to the bloom, so you want to remove it and recycle it through the furnace. The iron rich slag (which is usually quite runny), also decarburizes the bloom as it contributes more iron to it, so we want to ensure a constant flow of slag through the bloom. So tap some slag by poking through the hardened slag that has accumulated at the tap arch, but try to judge the amount to maintain a molten slag bath covering the bloom, so it doesn't burn up in the air blast. There may be a spongy sort of slag at the very bottom of the furnace also- scrape this out as well. Cool the slag (perhaps 10 lbs. worth), break it up, and at around ..
3:25 return it to the furnace with at least an equal weight of charcoal, for the first recycling charge. If you want to add limestone or wood ash as flux, do so with these recycling charges. 3:40 Recycling charge #2. 3:55 Recycling charge #3. You may continue this recycling regimen until the slag begins to get gummy and viscous (indicating a low iron content in the slag), if it has not done so already. 4:10 Add a charge of 10 lbs. charcoal and 10 lbs. of ore. We currently believe this charge of fresh ore has a strongly decarburizing influence. (Note: if you're trying to make steel instead of wrought iron, skip this step, and use more charcoal throughout all the previous steps). 4:30 Add 15 lbs. of charcoal, and let it burn down to tuyere level, which may take until 5:45 Cut the blast and remove the bloom. Gloat.
Eeeeeeeeee blacksmiths are numerous,
Aaaaaaah but those who can melt iron from stone have grown rare.
Beekillers are many.
Lionhunters are few.
-West African Song
back to home