Natural draft iron smelt
Added 2023-11-30 21:01:19 +0000 UTCI built a natural draft furnace and then smelted ore in it, obtaining a small amount of iron metal. A natural draft furnace is one where it works due to convection alone so no bellows or blowers are used. I've made a natural draft furnace before but this time I actually succeeded in making some iron. I then conducted a second smelt with left over slag and produced a smaller amount of iron. Much appreciated.
Comments
Yes I've seen this type before, it's like a see-saw. It seems to have been a similar species of bellow to one used in mainland China where a sort of door was opened and closed to a "room" that presumably contained a valve that admitted air into the furnace. This one was water powered and only single acting, see the first picture: https://en.wikipedia.org/wiki/Du_Shi
Primitive Technology
2024-01-20 08:13:10 +0000 UTChttps://youtu.be/95ZT_opuaSA?si=He9RN4TOsEKUSvdQ
Kenneth Crips
2024-01-20 07:14:38 +0000 UTCTake a look at these bellows.
Kenneth Crips
2024-01-20 07:14:31 +0000 UTCSo without a need for cast iron (i.e. a raw material to be refined into steel or wrought iron) Europeans avoided making it rather than not being able to make it.
Primitive Technology
2024-01-08 20:33:00 +0000 UTCThanks again.
Primitive Technology
2024-01-08 20:30:53 +0000 UTCCast iron is actually easier to make than bloomery iron, the iron I produce is probably 4% carbon cast content judging by it's brittleness and low melting point (I was able to insitu cast it in the knife video). There's a misconception that the technological bottle neck was temperature. But cast iron melts at 1150 c (as opposed to pure iron at 1500c+) Which can be achieved in an open forge. Most Europeans considered cast iron as furnace waste as it's often found on archaeological slag heaps. I think the real barrier to the blast furnace was to develop a fining technique to turn cast iron into malleable steel or iron by reducing carbon.
Primitive Technology
2024-01-08 20:26:30 +0000 UTChttps://www.sciencedirect.com/science/article/pii/S2667136021000017
Kenneth Crips
2024-01-08 19:55:45 +0000 UTCThe first link wasn't working anymore, not sure why it was working yesterday. I deleted it. But you know were to look now. There are so many different methods that were developed in Iron Age and Roman Europe. What is interesting to me is while Europe was producing bloomery iron, China had developed cast iron smelting by the 5th Century BC.
Kenneth Crips
2024-01-08 19:55:32 +0000 UTCThanks Kenneth, much appreciated.
Primitive Technology
2024-01-08 02:40:22 +0000 UTChttps://scholar.google.com/scholar?hl=en&as_sdt=0,51&as_ylo=1939&as_yhi=2024&q=pre-roman+iron+bloomery+furnaces+britain
Kenneth Crips
2024-01-08 01:52:22 +0000 UTCThis should keep you going for awhile.
Kenneth Crips
2024-01-08 01:52:15 +0000 UTChttps://chromewebstore.google.com/detail/unofficial-new-google-boo/hogcpkhknfgofogkkjlamicamnlbnagh
Kenneth Crips
2024-01-08 01:46:21 +0000 UTCThere is also Google Books. You can find a lot of good stuff there.
Kenneth Crips
2024-01-08 01:46:12 +0000 UTCGoogle Scholar is were you will find the academic studies on iron production in Iron Age Europe. And there a a lot of them.
Kenneth Crips
2024-01-08 01:32:15 +0000 UTCadd this extension to Chrome.https://chromewebstore.google.com/detail/google-scholar-button/ldipcbpaocekfooobnbcddclnhejkcpn?hl=en&pli=1
Kenneth Crips
2024-01-08 01:29:19 +0000 UTCThanks Kenneth, do you have a link to the roman natural draft furnaces? I've heard of them before but haven't found anything detailed on them, only some forums talking about it.
Primitive Technology
2024-01-08 01:19:16 +0000 UTCyou should emulate the Roman style natural draft furnaces. They were built with stone, and when in use were sealed up with mud and clay. If it rained and washed off all of the mud it didn't matter the stone furnace was still there. They are digging them up 2,000 years after their last use.
Kenneth Crips
2024-01-07 23:39:05 +0000 UTCJust an update on the bar, I heated it in the forge and pulled it out white hot. When I struck it with a rock it crumbled apart. I think it hadn't annealed properly. Back to the drawing board.
Primitive Technology
2023-12-11 03:44:49 +0000 UTCI expect it would have been expensive, considering he smelted the ore, processed the bloom and forged it.
Primitive Technology
2023-12-09 23:14:45 +0000 UTCThe Santoku knife he is making sells for about $1200 USD and has a 6 month delivery time.
Kenneth Crips
2023-12-09 23:08:49 +0000 UTCSimilar to the iron sand I smelted a while back, https://youtu.be/OPIUMpiV0IY?t=583 the iron made is sharp and corral like relative to the iron prills made from the iron bacteria. With the japanese tatara they produce blooms from iron sand with different carbon content, break it up and select pieces that vary from soft iron to steel depending on their need.
Primitive Technology
2023-12-09 23:06:28 +0000 UTChttps://youtu.be/tbbky_RwFyc?si=P_DPDv1tsxY3TRkb
Kenneth Crips
2023-12-09 22:51:26 +0000 UTCWhat you are trying to do with newer technology
Kenneth Crips
2023-12-09 22:51:17 +0000 UTCI managed to make cast iron forgeable in one video by melting the prills in the forge in front of the air blast. I was then able to hammer 3 pieces flat successfully https://youtu.be/pOj4L9yp7Mc?t=345. If this bar annealing doesn't work I'll just remelt the scrap in the forge and see if it makes a bloom like mass or resmelt it in the furnace and see if it makes a bloom. This approach is similar to a finery forge https://en.wikipedia.org/wiki/Walloon_forge.
Primitive Technology
2023-12-09 20:38:37 +0000 UTCI've considered it, the Bessimer converter would need a grate at the base and would need to be turnable to pour. Maybe like a modified tuyere that looks like a tobaco pipe that could fit over the spout of the blower. I don't know if the air blast would be strong enough and once it becomes molten. Also the blast would need to be applied without stopping as the iron would clog and freeze in the grate. Once it burns out the charcoal, the process is self sustaining.
Primitive Technology
2023-12-09 20:31:17 +0000 UTCI can see where that would be a problem. Have you adapted a Iron Age version of the Bessimmer process? Just blowing air into the crucible iron would burn off the carbon. Getting 1600°C air in should not be to much of a problem.
Kenneth Crips
2023-12-09 20:22:39 +0000 UTCMy iron has too much carbon, Just this week I melted the iron I collected into a mold insitu, in the open forge forming a crude, lumpy bar about 8 cmx 2.5cmx 1 cm. The prills are cast iron due to the high carbon which is good for casting (1150c melting point) but bad for forging as it's hard and brittle. So I heated it in the forge with wood for an hour to anneal the bar, bringing it back to soft iron (hopefully). I'll try and forge it and see how it goes. I'm filming the process and will upload the results.
Primitive Technology
2023-12-09 20:11:07 +0000 UTCOne thing to remember when you get enough bloomery iron to smelt, before you seal it up in a crucible be sure to place something burnable, like a dry leaf or a splinter of dry wood into it. What this will do it burn off any oxygen in the sealed pot.
Kenneth Crips
2023-12-09 19:29:02 +0000 UTCThat's the good thing about natural draft, you can film down the tuyeres while it's running. More shots like that to come hopefully. Thanks.
Primitive Technology
2023-12-05 19:42:56 +0000 UTCJust wow! Especially the sequences where I can see the slag flowing!
Hizuna
2023-12-05 18:17:14 +0000 UTCNo, I just go back to my house when I've finished and eat there. Thanks.
Primitive Technology
2023-12-04 19:29:10 +0000 UTCBack to a basics question, apologies if you've answered it over and over: are you staying at the site for days on end? And if so, where/what/how to you cook, eat and sleep when you're there.
Gabe Nathanson
2023-12-04 17:28:03 +0000 UTCThe video where I smelted gravity concentrated river sand was magnetite. After processing in the sluice, the sand was black and samples I took home stuck to a magnet without roasting first. It produces a similar yield to bacteria although the slag is more sharp and corral like. Thanks.
Primitive Technology
2023-12-01 19:44:19 +0000 UTCYes, I've thought about preheating the tuyere in a wood fire to save charcoal. Maybe a tuyere within a cross draft kiln before the air reaches the furnace. I'll see what I can come up with. Thanks.
Primitive Technology
2023-12-01 19:40:27 +0000 UTCI have a suggestion. It is obvious you source of iron is not the best. One thing that is archaeologically known to have been done in the iron age in Europe, is the use of magnetite stones to help refine their iron source. Australia has large deposits of this magnetic iron ore. It would be entirely within the theme of your show that you would could obtain magnetite as was done over 2,400 years ago in Europe via the extensive trade networks in place. Just a few stones would be of great help in concentrating your bacterial iron source.
Kenneth Crips
2023-12-01 17:52:29 +0000 UTCGreat work, would love to see more designs, hopefully reduce the amount of work per unit of output. Have you considered pre-heating the air used in combustion in a separate fire/basic heat exchanger? (e.g. a separate fire around a longer tuyere)
Radu Stefan
2023-12-01 11:43:04 +0000 UTCShort answer 1100 to 1200 c I reckon. I tend to think it's on the cold side because the slag was so viscous, it should be dripping like water for a good smelt. Modern recreations of natural draft furnaces have reached 1400 c and temperatures of 1600 c are undoubtably attainable with sufficient tuyere area and furnace height according to "The mastery and uses of fire in antiquity" by J.E. Rehder.
Primitive Technology
2023-12-01 06:58:29 +0000 UTCJohn, any idea how hot it got in there?
Chris Jones
2023-12-01 06:24:23 +0000 UTCThanks. I was lucky to get the shots of the slag dripping through with the Iphone. You can focus shots down the tuyere during operation, something that can't be done when using a blower blocking the view. As for the iron bacteria, I think it may be something to do with white clay contaminating batches. The reason I say this is because I tried smelting the bacteria when it grows in white clay in certain locations and it doesn't produce iron despite getting a good melt. Also, in the video where I made the knife, the ore was producing more iron per smelt suggesting that subsequent smelts with ore from the same location might be contaminated with clay due to changed stream conditions higher up. That's my 2 cents anyway, at least it's still making some iron even if it takes more ore. Thanks.
Primitive Technology
2023-12-01 02:08:52 +0000 UTCAwesome work, as always! Glad your camera didn't melt while taking those close shots, that's some truly golden footage A thought about iron bacteria, there may be some other metal contaminants in the resulting paste; some species can also use things like manganese as electron carriers, and might retain some other stuff. From what little research there is on the subject, it sounds like this varies based on how close you are to acidic thermal springs (maybe). Who knows if that's affecting your overall yield, though-- I guess short of magnets, it's probably really difficult to separate those. Some sort of flotation separation? Overthinking aside, super cool-- hope you didn't get any burns.
Pinkus McEverclear
2023-12-01 01:31:45 +0000 UTCA good resource, Africa still has natural draft furnaces that have survived till modern times. the book Mastery and use of fire in antiquity has the dimensions of a natural draft furnace for smelting iron. 1.5 m tall, 40 cm wide, 4 x 4cm diameter tuyeres and using 3.5cm average lump diameter charcoal.
Primitive Technology
2023-12-01 00:47:04 +0000 UTChttps://unesdoc.unesco.org/ark:/48223/pf0000133843
Kenneth Crips
2023-12-01 00:36:38 +0000 UTC8th Century BC Chinese technology http://donwagner.dk/Fate/Fate_Figs/Fate_Figs.html
Kenneth Crips
2023-12-01 00:25:27 +0000 UTCThis one uses natural draft to make iron prills and then they cast and forge the iron: https://www.exploring-africa.com/en/blog/867/blacksmiths-koni
Primitive Technology
2023-11-30 22:43:01 +0000 UTCSome natural draft furnaces I studied for this project: https://www.arup.cas.cz/wp-content/uploads/2019/11/10_Madera-Kik-Suliga_435-449_web.pdf
Primitive Technology
2023-11-30 22:41:34 +0000 UTCI book marked it. Thanks.
Primitive Technology
2023-11-30 22:39:47 +0000 UTCYes, I don't think it got over 1200c this time as an average temperature. Needs to be blindingly white like looking at the sun.
Primitive Technology
2023-11-30 22:37:39 +0000 UTChttps://muse.jhu.edu/pub/1/oa_monograph/chapter/2471261
Kenneth Crips
2023-11-30 21:41:40 +0000 UTChttps://www.pinterest.com/pin/347340190017462304/
Kenneth Crips
2023-11-30 21:33:22 +0000 UTCThis might be of help.
Kenneth Crips
2023-11-30 21:33:12 +0000 UTC
