Manufacturology

Ironmaking at the National museum of science and technology, Stockholm 2005

Back in 2005, I took part in an event at Tekniska museet (the National museum of sci­ence and tech­nol­ogy) in Stock­holm where we demon­strated pre–industrial Swedish and Japan­ese tech­niques for iron and sword mak­ing. Quot­ing another post that I wrote two weeks ago:

Those of you who read Swedish may have seen that there is a page on my blog called “Svär­dens mästare”, which trans­lates to “Mas­ter of the swords” in Eng­lish. I trans­ferred this page with­out fur­ther ado from my pre­vi­ous web site and have yet not taken the time to trans­late and rework it. The page is a brief account of an event at the National museum of sci­ence and tech­nol­ogy in Stock­holm in 2005 where Swedish and Japan­ese met­al­lur­gists, sword­smiths and oth­ers par­tic­i­pated. Myself I was respon­si­ble for the con­struc­tion and oper­a­tion of a shaft fur­nace rep­re­sen­ta­tive of pre–industrial iron making.

I finally decided to remove that old page. I’ve there­fore decided to write this fairly lengthy post for future record. Below, you’ll find some infor­ma­tion about, and pho­tos from, the event, which took place at the National museum of sci­ence and tech­nol­ogy in Stock­holm on Sep­tem­ber 10 and 11, 2005.

Prepara­tory activities

As men­tioned above, a lot of par­al­lel activ­i­ties took place dur­ing the week­end at the museum. How­ever, from my per­spec­tive, the most impor­tant activ­ity was the con­struc­tion and oper­a­tion of a coal–fired shaft–type bloomery fur­nace. I had been involved in the plan­ning of the event since sev­eral months, and I and the fur­nace group mem­bers, who were stu­dents at Högskolan Dalarna by that time, had learned and prac­tised fur­nace con­struc­tion and oper­a­tion in advance.

I’m oper­at­ing the bel­low at Ham­marede smithy. (Click to enlarge.)

Two small ingots — the result of our two runs dur­ing our stay at Ham­marede. (Click to enlarge.)

Dur­ing the sum­mer we had been on a two day camp at Ham­marede smithy to learn from the expe­ri­enced K.-G. Lind­blad who had been mak­ing bloomery fur­naces for 20 years. We had then con­structed and oper­ated a fur­nace in Bor­länge only a few days prior to the event at the museum.

Under K.-G.‘s super­vi­sion, we man­aged to com­plete two runs at Ham­marede. K.-G. also helped us to forge the loupes, or blooms, into small ingots of about 1.4kg each. The loupe is first com­pressed on a stump in order to make use of the heat from the fur­nace as seen in the big pic­ture at the top of this post. After that comes a lot of hard work in the smithy before you have those beau­ti­ful com­pact ingots seen above.

After the sum­mer we built a new fur­nace in Bor­länge which was to be demon­strated dur­ing the intro­duc­tion of new stu­dents at the Mate­r­ial design pro­gramme.

Our fur­nace was a copy of the one we used at Ham­marede. Vari­ants of this fur­nace type has been used since the iron age, and was, despite the inven­tion of the blast fur­nace, still used for small scale iron mak­ing until the 19’th cen­tury in some areas. A patent for an improved fur­nace, sim­i­lar in prin­ci­ple but fired with stone coal instead of char­coal is described by Her­bert (1849). Appar­ently this fur­nace was still con­sid­ered indus­tri­ally impor­tant in the early 19th century.

We were encour­aged when, despite some dif­fi­cul­ties, we man­aged to pro­duce a nice iron loupe.

The height of the ver­ti­cal shaft was deter­mined from our design with two lay­ers of ver­ti­cally stand­ing bricks put on top of each other. The shaft was sup­ported by an insu­lat­ing layer of gravel con­tained inside a log wreath. The arrange­ment of bricks can be seen in the draw­ing and photo below. The photo shows the con­di­tion of the fur­nace after the run on Sep­tem­ber 2. We had quite a bit of a prob­lem to get the loupe out of the shaft, which resulted in severe dam­age to the furnace.

My own hand made draw­ing of the fur­nace with bel­low in place.

Dam­ages after dif­fi­cul­ties to get the loupe out of the shaft. (Click to enlarge.)

Peter Mats­son made the wreath for the Bor­länge fur­nace seen above. The fancy log wreath seen in the pic­tures below from the museum was made by a pro­fes­sional carpenter.

The fur­nace at the museum

On Mon­day, Sep­tem­ber 5, I drove from Bor­länge to Stock­holm together with Robert Ståhl to con­struct the fur­nace at the museum. We brought a trailer fully loaded with tim­ber, bricks, clay pow­der, as well as the tools needed for con­struc­tion and oper­a­tion. I had also arranged for one m³ of rough gravel, as well as a pal­let of char­coal, to be deliv­ered in advance at the museum.

Dur­ing Mon­day we con­structed the fur­nace that would be used dur­ing the next week­end. The shaft was laid with clay and ver­ti­cally stand­ing bricks. It was lined with clay on the inside and a log wreath was used to con­tain the insu­la­tion, con­sist­ing of approx­i­mately 300kg gravel and soil that we dragged across the museum’s yard in 10 litre buckets.

Brick­lay­ing is a messy story. The mor­tar con­sists of clay, sand and horse manure (if avail­able), mixed with water to a fairly loose bat­ter. The best fin­ish is obtained if you work with your hands as the mor­tar is placed on, and smears with water so that the sur­face becomes smooth and fine. When then fur­nace is ready, it is dried through slow heat­ing by wood with­out blast­ing, until the moist has been dri­ven out of the mud. At this stage, heat­ing should be quite cau­tious in order to avoid cracking.

Then, on Fri­day Sep­tem­ber 9, we went again with a fully loaded trailer from Dalarna in the direc­tion of Stock­holm. More than a few peo­ple were prob­a­bly turn­ing their heads when we passed, because the trailer was dom­i­nated by a large bel­low — our newly built two cham­ber bel­low with an esti­mated blad­der capac­ity of up to 800 litres per minute. In addi­tion, we brought fire wood, iron rods, pli­ers, some stumps and other stuff needed for the fur­nace operation.

The fur­nace at the museum with Kim Svens­son and Peter Mats­son. (Click to enlarge.)

Lift­ing the loupe from the shaft for com­pres­sion on the stump. (Click to enlarge.)

We made one run each on Sat­ur­day and Sun­day. Each time we charged a total of about 10kg ore added in amounts of about 1kg every 20 minute. For each charge, we added about twice the amount of char­coal. Dis­charg­ing of the loupe was sched­uled for two o’clock, and by that time a fairly large crowd had gath­ered to see the show. This time we man­aged to get the loupe out of the fur­nace with­out too much trou­ble. Worse was that the process took longer than expected, but the crowd seemed to be patient and peo­ple stayed around until the end.

About 1500 peo­ple paid the entrance fee to visit the museum dur­ing the week­end. An unknown num­ber of peo­ple chose not to pay the entrance fee, happy to stroll around and look at the activ­i­ties outdoors.

My rough hand drawn sched­ule for the dura­tion of the three days, which I made before the event, is seen below. This reflects my esti­mates in advance. How­ever, the actual out­come cor­re­lated fairly well with the plan.

A num­ber of inter­est­ing activ­i­ties took place in addi­tion the our fur­nace. A pro­fes­sional Japan­ese samu­rai sword pol­isher worked for two days in the museum. There were demon­stra­tions of the Japan­ese tra­di­tional iron­mak­ing in a tatara fur­nace. A Japan­ese black­smith made tools and axes in a small forge — he stood in a hole that he had dug in the sand out­side the museum. Rolled bam­boo mats were chopped up using samu­rai swords (katanas) and beau­ti­ful 1200AD style Euro­pean swords forged by Peter Johns­son. I’m not going to write about that now, not because of a lack of inter­est, but because with this post I wanted to doc­u­ment our iron­mak­ing efforts.

Media cov­er­age

We received some good pub­lic­ity the days prior to the event. On Fri­day Sep­tem­ber 9 there was half a page in SvD on show­ing Japan­ese and Euro­pean swords, sup­ple­mented by pho­tos of our instal­la­tions at the museum. DN “På stan” con­taind a note about the event. TV4 were broad­cast­ing live from the museum dur­ing the cul­ture news. Our bloomery fur­nace was seen in the back­ground while we fired to dry the fur­nace. Chan­nel 1 had made a record­ing from the museum dur­ing the day before and showed it dur­ing their cul­ture news on Fri­day. Since nobody else wanted to be on the radio, I myself had the plea­sure to have a five minute con­ver­sa­tion about swords, samurai’s, and iron­mak­ing live in Radio Stockholm.

Pub­li­ca­tions

In addi­tion to the infor­ma­tion here on Man­u­fac­tur­ol­ogy, two reports from the event are avail­able if you read Swedish. Imme­di­ately fol­low­ing the event I wrote an arti­cle which was pub­lished in Bergs­man­nen [Storck, J. et al., “Svär­dens mästare möttes”, Bergs­man­nen, nr. 6, 2005] (in Swedish). You can down­load it here: Svär­dens mästare möttes (757 kB). The iron­mak­ing tech­nolo­gies, i.e. the bloomery fur­nace and the tatara fur­nace, were also described in another arti­cle in Pop­ulär Arke­ologi: [Mag­nus­son, G., “Samu­ra­jer och vikingar — så smidde de svär­den”, Pop­ulär Arke­ologi, nr. 3, 2005] (in Swedish).