Natural Draft Bloomery?

[Richard V]

In my readings of older books (most online) on iron bloomerys and blacksmithing I keep running across references to natural draft bloomerys. It is almost always the exact same two statements made "These pipes, called tuyeres, allow air to enter the furnace, either by natural draft or by forced with a bellows." OR "The original bloomery process was carried out in pits lined with refractory clay or on stone hearths; these furnaces used a natural draft supplied through a tuyere in the lower part of the hearth." I have yet to see a illustrated or explanatory description of how you would go about creating a natural draft bloomery. I find quite a bit on bellows or other forced air type furnaces, just not on a natural draft bloomery. Can anybody help clarify how you would go about creating such a bloomery?

Just curious and can't let it go....

Richard V

[Michael]

I do recall reading somewhere about a bloomery being located in a place of naturally windy conditions, such as a valley or gulch near the edge of a topographical transition from plains to foothills. I suppose coastal could work as well. The idea being a fairly constant wind, perhaps directed by some strategic stone or earthworks, into a tall bloom furnace excavated out of the (hopefully) ore bearing earth.

A combination of ore rich location, natural wind and plentiful timber for charcoal production would lend itself to a bloomery the way water falling down hills lends itself to water powered mills.

[yesteryearforge]

There were lots of them here in Virginia and other east coast states I suppose
George washington operated several and you may find some info by that route.
There are still remnants of them thru - out the Peidmont region of Virginia

[Dave Budd]

in sri lanka they use wind drived furnaces. Tey are large D-shaped structures with a row of tuyeres along the flat side, which is facing the monsoon winds. A friend of mine (Dr Gill Juleff) wrote her Phd on the subject and the pictures of those furnaces running at night are amazing!

[Richard V]

Thanks much everybody, that at least gives me some more jumping off points for research. I have also requested, through my local university library, a copy of David J Killick's Phd thesis Technology in its social setting: bloomery iron smelting at Kasungu, Malawi, 1860-1940 (circa 1990 Yale) as I have found several sources pointing to his work as a reference.

Dave Budd I will look up Dr Juleff's work as well, and I would like to say a special thanks to you. We have emailed back and forth a couple of times and you have always been helpful and insightful. If I had the funding I would love to jump the pound and take every course you offered.

That is not to take away from anybody else on the site. Everybody at iforgeiron has always been helpful, and down to earth....... iron oxide mostly, but down to earth none the less :D

Richard

[Frank Turley]

The induced draft is shown in the excellent film of Dogon smiths in Mali. Their iron furnace had several tuyeres around the base a little above ground. The film didn't dwell on the how-to aspect, but it was clearly shown that the heat of the charcoal affected the draft. The film was made by Swiss anthropologists: "Inagina the Last House of Iron."

[trying-it]

Richard not sure if you had seen this article yet, but go to this link: (and then click "look inside" feature for a pic and diagram)

http://rd.springer.com/article/10.1007/BF03220550

Stan

[pkrankow]

http://www.waymarkin...a0-56009536d09f
http://www.oldindustry.org/OH_HTML/OhioIron.html

I don't know which are natural draft and which are forced air, but there are a lot of furnace ruins and restored ruins to look at all over the world.

Phil

[Richard V]

Guys thanks so much for the links, and the info. Phil thanks for the new pics of furnaces I hadn't seen yet, trying-it I hadn't seen that link yet, but I am reading through it now, thanks. And Frank Turley thanks SO MUCH for that info I am watching the preview of the film now, and am already trying to find a way to obtain a copy.

Anybody else keep them comming, I just can't get enough watching the old ways.

Richard V

[Bentiron1946]

I watched the film on the Dogon smiths and the explanation was that once the fire starts drawing and the hotter it gets the more air is drawn into the furnace through the tuyeres . It isn't dependent on how much ambient wind is blowing on any given day or not but on how hot the internal fire is in the furnace. It is like a side draft chimney on a forge, as the chimney gets hot the better it will draft. As the heat increases in the bloomery more air is more through the tuyeres and at a higher velocity as this happens it increases the temperature, it is a compounding effect of heat and increased oxygen introduce to the furnace.

[doc]

Here is a natural draft furnace of an African style I helped Jake Kean build along with Lee Sauder, Michael McCarthy ,Jesus Hernandze and others a few years ago.

[Richard V]

David J Killick's Phd thesis Technology in its social setting: bloomery iron smelting at Kasungu, Malawi, 1860-1940 (circa 1990 Yale) *REVIEW*

Let me boil it down for you......

#1 - They didn't have sex for two months while the process was ongoing
#2 - We forgot to ask that question
#3 - We forgot to record the answer to that question
#4 - They didn't have sex for two months while the process was ongoing
#5 - We didn't get a chance to talk to any actual iron smiths, just the guys who worked with them, and some guys who knew some guys, who had heard about the iron smiths.....
#6 - We burned up eight years of grant funding in five years..... Party in Africa!
#7 - Seriously..... No sex for TWO MONTHS!

Yeah so as actual useful information goes.....

#1 - This guy can reference other peoples work like nobody I have seen before. IE For more info see John Doe - This is how they did it.pdf from Anyplace, Anycollege, anycountry, circa Thisdate... (Got a nice list of gotos from it)
#2 - ........

I don't usually like to be critical of anybodies work who has done ANY kind of research/actual work, but since this guy has the research chops of a deaf blind monkey in a video game store..... yeah....

Richard

[ThomasPowers]

The Sri Lankan furnaces were blown, (actually sucked as the wind passing over the top of the furnaces had a greater affect than the wind hitting the faces with the tuyeres according to the write up in nature...)

The self drafting furnaces are based pretty much on the same principle as the side sucker chimney for a forge. Hot air rises pulling in more air.

All the furnaces we toured at the IronMasters conference in Ohio were blown, some even by steam engines! Most were cold blast as I recall