ancient bloomery

Over the past 25 years, metallurgist Ivo Janez Cundrič has explored the Alpine region of Bohinj in search of “forgotten gold”—iron, a prized material of the Iron Age, valued above gold for its strength and utility.

This study presents the entirety of his research, focusing on the Bohinj region in Slovenia—an Alpine valley with a rich history of iron production, spanning from the Iron Age through the Late Roman period, the Middle Ages, and into the modern era, up to the year 1890.

His findings support historian Alfonz Müllner’s general claims regarding the advanced metallurgical skills of ancient ironworkers. Among the most remarkable discoveries is the bloom Dunaj 2, which Cundrič identified as clear evidence of carburization (carbon enrichment of iron). This represents a high-level innovation achieved by Iron Age blacksmiths in Bohinj. Intriguingly, the same advanced technology re-emerged 2,000 years later at the Bistrica Forge (fužina Bistrica), located not far from Ajdovski Gradec- the Guardian of Ancient Bohinj.


Zadnjih 25 let je metalurg Ivo Janez Cundrič raziskoval Bohinj, alpsko pokrajino in  njeno »pozabljeno zlato« – dragoceno kovino železne dobe, dražje od zlata prav zaradi trdnosti in uporabnosti.
Študija predstavlja njegovo celovito raziskovalno delo, pri čemer se osredotoča na Bohinjsko dolino v Sloveniji – alpsko pokrajino z bogato zgodovino produkcije železa, ki sega od železne dobe skozi pozno rimsko obdobje, srednji vek in vse do moderne dobe, do leta 1890.
Njegove ugotovitve potrjujejo splošne trditve zgodovinarja Alfonza Müllnerja o visoki ravni metalurškega znanja starodavnih železarjev. Med najbolj izstopajočimi odkritji je volk Dunaj 2, ki ga je Cundrič prepoznal kot jasen dokaz ojeklenitve (obogatitve železa z ogljikom).To predstavlja visoko raven tehnološke novacije, ki so jo dosegli bohinjski kovači v času železne dobe. Zanimivo je, da se je enaka napredna tehnologija ponovno pojavila dva tisoč let pozneje v fužini na Bistrici, nedaleč od Ajdovskega gradca, stražarja antičnega Bohinja.

In the southern part of Norway the nature is varied with a long coast line, there are good agriculture areas, large valleys, woodlands and low-and high mountain areas. In many parts of this vast area we find extensive iron production in the period from 300BC -AD1850. In this paper we will concentrate on the first 700 to 800 years where our aim is to take a detailed look at the shaft furnace with slag pit. In this period we see a picture of three different traditions in our area. The type which dominates is a large shaft furnace with slag pits: the Østland furnace. Another and smaller type is a Continental furnace which has its nearest parallels in Snorup, Denmark. The third type is as yet only found twice in the south-east Norway, but it is the standard in Trøndelag in the same period (Trøndelag furnace). In the presentation we will focus on the types and discuss differences such as organization and localisation in a local and regional perspective. Finally, we raise the horizon, looking at the amount of the production, and at the power situations, network alliances, trade routes, and the Roman import material in Norway.

Järnframställning i blästugn-en uppdaterad kronologi. (An updated chronology of iron production in bloomery furnaces in Sweden.) Fornvännen 120. Stockholm. The production of iron in bloomery furnaces has long been recognised as one of the most significant forms of non-agrarian resource extraction during the Iron Age and a cornerstone of societal development in Sweden. This production enabled the creation of advanced agricultural tools, supported the construction of large boats, and became a vital commodity in Late Iron Age trade networks. This article presents the results of compiling a database of approximately 1,250 radiocarbon-dated (carbon-14) samples from facilities associated with iron production in Sweden. The samples have been calibrated and analysed using KDE analysis (Kernel Density Estimation) to generate a graphic representation of the temporal development of iron production. The results offer a more robust and statistically grounded model of early iron production in bloomery furnaces than previously available. The use of standardised statistical models enables the exploration of iron production as part of the broader exploitation of non-agrarian resources, revealing how various activities fluctuated and interacted over time. Both national and regional analyses provide insights into spatial differences and similarities across periods. The database will be made publicly accessible through Zenodo, facilitating further research and collaboration.

On the occasion of the inauguration and the formal scientific opening of the iron smelting Museum in Somogyfajsz, an international archaeometailurgical workshop was organised, with participating archaeologists and archaeometallurgists from Austria, Croatia, Czech Republic,  Germany, Great Britain, Italy, Norway, Romania, Slovakia and Hungary. Before the official opening of the workshop, the participants visited the Roman and medieval monuments of Sopron and the remains of the early medieval iron smelting furnances, which are exhibited in the archaeological department of the Sopron Museum. Afterwards, the researchers observed the medieval iron ore mining pits of the forest of Kópháza, near Sopron.
This publication collects the presentations delivered in the two sessions of the workshop. They were completed with some other writings, whose authors were not able to take part in the meeting in May of 1997. The lectures of  the Ukrainian collegaues, are also published, which were held on the Metallurgical Day in Somogyfajsz in 1998, organised by the National Hungarian Mining and Metallurgical Association, together with the Industrial Archaeological and Archaeometrical Working Committee. Travelling from Sopron to Somogyfajsz, the participants of the meeting viewed the late Roman iron blooms weighing 50-60 kilograms in the Balaton Museum of Keszthely. Then, in Somogyfajsz, they observed the iron smelting workshop from the 10th century. At the same time with the discussions, a demonstrative smelting was carried out in an iron smelting unit, which was reconstructed on the model of the workshop in Somogyfajsz.

Az avar kori és Árpád-kori vaskohászat régészeti emlékei Pannóniában. Magyarország iparrégészeti lelőhely-katasztere I. Vasművesség. The Archaeometallurgical Sites in Pannonia from the Avar and Early Árpádian Pariod. Register of industrial archaeological sites in Hungary I. Ironworking. Sopron, Hillebrand Nyomda (2000).

The author gives a short review about the main results of the research on the field of the archaeometallurgy in Europe and in Hungary. Then methods of archaeometallurgical excavations are discussed. The main part of the book contains the data about the excavated archaeometallurgical sites (the firts part of the Register of early Industrial Archaeological Sites in Hungary), with special regards to the remains discovered after the publication of the book written by HECKENAST-NOVÁKI-VASTAG-ZOLTAI (1968) about the early Medieval iron production in Hungary. During the last 30 years several iron-smelting workshops with different types of furnaces have been discovered.

Bilaga 1. Provtagningsplatsernas lägeskoordinater Bilaga 2. Vattenkemiska analysmetoder Bilaga 3. Analysresultat för vattenkemi-tabeller Bilaga 4. Analysresultat för vattenkemi-figurer Bilaga 5. Ämnestransporter och arealspecifika förluster-tabeller Bilaga 6. Ämnestransporter-figurer Bilaga 7. Syrgas-och temperaturprofiler-figurer Bilaga 8. Växtplankton-biovolymer Bilaga 9. Bottenfauna-tätheter och biomassor Bilaga 10. Resultat från provfiske inkl kvicksilver-och metallhalter i fisk-7-Under perioder med stabil temperatur skiktning uppträder ibland dåliga syrgasförhållanden framförallt i de mer näringsrika sjöarna fr o m Södra Barken och nedströms i vattensystemet. Med undantag för tillfällen med förhållandevis låga syrgashalter i de mindre sjöarna i den övre delen av åsystemet, är syrgasförhållandena överlag goda i Kolbäcksåns sjöar. Kolbäcksåns sjöar och vattendrag har i allmänhet en god buffertkapacitet. Endast i den övre delen av vattensystemet förekommer period vis låga pH-värden och låg alkalinitet i bl a Pellabäcken och Saxen, vilka ligger i några av de få områden inom vatten systemet som inte kalkas eller har kalkats tidigare. Metallföroreningsmönstret i sjöarnas vatten och de metallmängder som transporteras igenom vattensystemet följer varandra väl. Saxen är den mest metallförorenade sjön, med förhöjda halter av koppar, zink, bly och kadmium, vilket beror på den tidigare gruvdriften i Saxdalen. Saxens påverkan på resten av Kolbäcksån varierar mycket mellan olika metaller, men generellt kan man säga att de mer lättrörliga metallerna zink och kadmium har en större och mer vidsträckt påverkan än mer svårrörliga metaller som bly och koppar, vilka tenderar att stanna kvar lokalt i sjöns sedimenten. Förhöjda halter av flera metaller återfinns även stundtals i Stora Aspens botten vatten i samband med dåliga syrgasförhållanden och låga pH-värden i augusti. Legeringsmetallerna krom, nickel, kobolt och volfram tillförs vattnet framförallt i systemets nedre industritäta del. Växtplanktonbiovolymerna i Kolbäcksåns sjöar var i år överlag på en förhållandevis normal nivå. De högsta biomassorna uppnåddes som vanligt i de näringsrikaste sjöar i systemet, dvs Trättens södra bassäng (Trätten S), Stora Aspen och Östersjön. Kisel alger var generellt sett den viktigaste planktongruppen, men även guld-och rekylalger utgjorde ett betydande inslag. Cyanobakterier (blågrönalger) var däremot vanliga i St. Aspen. Årets bottenfauna sammansättning i sjöarnas strandzoner (litoral) uppvisade i år färre antal taxa, men med en artsammansättning som är normal för sjöarna. Även tätheterna på sjöarnas djupbottnar (profundalzoner) var överlag lägre i år jämfört med de höga tätheterna under fjolåret. Provfiskeresultaten och metallanalyserna visar sammantaget på likartade resultat jämfört med den tidigare undersökningen 1996. Totalt erhölls 2 734 fiskar fördelade på 12 arter. De vanligaste arterna var abborre och mört, vilka fångades i samtliga sjöar. Andra vanliga arter var gers, björkna och braxen, medan nors, siklöja, gös, lake, gädda, asp och löja förekom i mer begränsad omfattning. Tre exemplar av den rödlistade arten asp fångades i Östersjön. Endast tre stycken gäddor fångades, varför kvicksilveranalyserna kompletterades med prov från gös och abborre. De största fiskfångsterna såväl antals-som viktmässigt erhölls i de två mest näringsrika sjöarna Östersjön och Stora Aspen. I dessa sjöar utgjorde karpfiskar (vitfiskar) hälften eller mer av vikten i näten, vilket är vanligt i näringsrika sjöar. Kvicksilverhalten i abborrmuskel från Övre Hillen var något högre än halten i fisk från de övriga sjöarna. Halterna i abborre som är större än ca 20 cm från denna sjö är nära det gällande gränsvärdet för saluförande på 0,5 mg/kg. Jämförelsevis höga halter av koppar, zink, kadmium och bly återfanns i abborrlever från Saxen, vilket överensstämmer med de höga halterna av dessa metaller i Saxens sediment. I sedimentundersökningen 2001 noterades även förhöjda halter av nickel, kobolt och volfram i St. Aspen och sjöarna nedströms, vilket även speglas i jämförelsevis högre halter av nickel och volfram i fisken från St. Aspen, Åmänningen och Östersjön.

The Industrial Archaeology Working Group of the Veszprém Regional Committee of the Hungarian Academy of Sciences made trial excavations in the forest near Somogyfajsz, with the financial support of the Hungarian Mining and Metallurgical Society (OMBKE) and sponsoring from the ELTE (Eötvös Loránd University, Geophysical Department, Budapest), for the sake of archaeomagnetic age determinations of the excavated furnaces). Along with the completion of the first trial trenches, geomagnetic measurements were carried out (by J. Verő, MTA GGKI, Sopron) to determine the size of the heap of iron slags and to define the outlines of the workshop without cutting away any trees. These geomagnetic data refer to furnaces or to the interiors of workshops.
The slags and the fragments of furnaces found on the surface, (especially the high positive nT values of the slags), indicated that both the technology and the raw materials used on this site were different from those which we have been familiar with from excavations around Sopron (NW-Hungary). During the excavation, the raw material used for the smelting: limonite blocks (bog ore) of the size of a human head were identified in the flood area of the Koroknai brook, within a radius of 2-3 km from the smelting site. The workshop pit, with a diameter of 16 m, where remains of 16 iron-smelting furnaces were excavated (1988), verified our assumptions. The average basin-diameter of the furnaces built into the side wall of the work shop pit was 35-40 cm. Their interior was pear-shaped, with a height of about 70 cm in the inner part of the shaft.
The second workshop-pit (1995) which is displayed in the Bloomery Museum in its original form has a quadrangular ground plan, with rounded corners. Its sides were 6m long, with an entrance from the previous workshop, to east. The furnaces were standing along the southern, western and northern walls, in a distance about 3 metres from each other, so that the blowing could be carried out without any difficulties beside all three furnaces. The charcoal and the iron ore was filled through the throat-opening. The places where the raw materials (and fuels) were piled up were indicated by red and black surfaces because of charcoal and roasted ore respectively, both with a diameter of 100cm, discovered at the outside of the workshop-pits beside e.g. furnaces No. 17 and 19. The smelting was carried out by two workers: one of them was working outside the pit, on its upper edge, while the other one operated the bellows inside the pit.
The possibly amount of iron produced in the Somogyfajsz workshop: Beside the 21 excavated furnaces, some more can be expected on parts of the workshop which could not be investigated yet. The 500 tuyeres found on the site indicate at least 500 smeltings. If, we suppose that about 2.5 kg of iron (or steel) was produced by each smelting process, some 1250 kg, that is one and a quarter metric tons of iron was produced in this workshop. Supposing about 500 smeltings for the workshop altogether, about 20iron blooms were produced in each furnace which made altogether about 50 kg of iron.
As regards absolute chronology, the ironsmelting workshop can be dated according to the pottery decorated with undulating lines as well as on the basis of 14C , (Debrecen, ATOMKI, E. Hertelendi)  and archeomagnetic data (ELTE Departmnt of Geophysic, P. Márton) to the 10th century.

Complimentary research to the paper 'Brokes Wood Blommery Furnace' and offers scientific analysis of several examples of recovered worked iron blooms. The work was commissioned by the Wealden Iron Research Group (WIRG) and undertaken by Dr Alan Davies. The samples are from a collection of bloomery material collected during excavation of a middle Iron Age bloomery furnace at Brokes Wood in West Kent in 2014/15. It is believed the assemblage may well be one of the largest collection of such in Southern Britain.

A preliminary review of Kent's oldest carbon dated Bloomery Furnace, at Brokes Wood in Southborough, and dated to around 340 BCE. Evidence of the process of primitive iron production has been compiled and presented within the review. The research also produced a significant collection of worked blooms and bloom fragments. Further evidence suggested an area of deliberate pit deposition of fragmentary iron in a possible ritual context. The site also produced evidence of late Neolithic and early Bronze Age activity.

Sebastian Sonntag, Daniel Riemenschneider & Manuel Zeiler (2023):
Nach der Jahrhundertflut – Denkmalschäden im Sauerland und südlichen Ruhrgebiet. Archäologie in Westfalen-Lippe 2022, 259-262.

In July 2021, heavy rainfall caused massive damage in the southern Westphalian region of Sauerland and the southern Ruhr area. Hundreds of archaeological sites were affected, as shown by prospections and evaluations carried out in 2022. At high and middle altitudes of the Central German Uplands, for example, sections of the valley sides were washed away, destroying numerous pile dwellings and smelting sites.

Im Juli 2021 verursachten Sturzfluten aufgrund extremer Regenfälle massive Schäden im südwestfälischen Sauerland und im südlichen Ruhrgebiet. Hunderte von archäologischen Fundstellen waren betroffen, wie Prospektionen und Auswertungen im Jahr 2022 zeigten. In den Hoch- und Mittellagen des Mittelgebirges wurden beispielsweise Teile der Talflanken weggespült und zahlreiche Meiler- und Eisenverhüttungsplätze zerstört.

Unpublished report of two excavations made in 1985 by the author and Wiking Wedberg, Arkeometallurgiska Institutet, Stockholms Universitet.

The excavations were made of two iron production sites from the period c. 400-800 AD, i. e. the Migration and Vendel/Merovingian periods. The sites were situated along the shores of lake Åmänningen in northern Västmanland in Central Sweden.

One larger excavation was made at Västervåla 47. The site consisted of three heaps of slag and two well preserved bloomeries. Ore in form of limonite was used and fragments of lake ore was found.

A documentation was also made of a disturbed but even larger site nearby, Västervåla 60. 

The sites are interpreted as sites with an over-production of iron for the market in the more densely settled areas in Central Sweden.

Landscape, process and economy in the bloomery iron production during AD 400-1000 are all integrated in this paper initiated by an archaeological excavation of a bloomery site in Motala in Östergötland, southeast Sweden. This site is one among other contemporaneous sites with similar features, such as long-term iron production and a location in the landscape within easy reach of communication routes and, most importantly, access to the vital raw materials ore and wood. The site is placed in a rich region with several high-status features, such as richly furnished graves and settlements. We evaluate the transfer of knowledge and skills in a landscape perspective. Interactions in a complex network involving various entrepreneurs, from producers to consumers, are suggested as central. The major focus is on the importance of the organisation, the economic point of view, as well as quality and trade.

Tijdens het onderzoek zijn in totaal 259 stuks slak verzameld met een totaal gewicht van 34.498 g. Het gevonden slakmateriaal wijst erop dat in de 9de /10de eeuw ijzerproductie heeft plaatsgevonden op Wijchen-Oostflank. Tijdens het proefsleuvenonderzoek werd al een ijzeroven gevonden en twee mogelijke vondsten. De definitieve opgraving heeft laten zien dat zich hier nog drie vergelijkbare ovens bevinden en een ermee te associëren afvalkuil. De kuilen wijzen samen met de slakken op het gebruik van kuilslakovens, wat opmerkelijk is voor deze periode. Bekend is namelijk dat in de Vroege/Volle Middeleeuwen vooral tapslakovens werden gebruikt. Verder is op basis van een aantal complete smeedhaardslakken uit een waterput uit de Volle Middeleeuwen aangetoond dat in deze periode ijzer werd gesmeed in de nederzetting op Wijchen-Oostflank.

Tijdens de opgravingen op de Kerkakkers bij Hoogeloon is een grote hoeveelheid slakmateriaal en limoniet aangetroffen. Voor de analyse waren 1.836 fragmenten slak en 885 fragmenten limoniet beschikbaar.

Het limoniet blijkt te zijn gebruikt als bouwmateriaal, wegverharding en als erts voor de productie van ijzer. Enkele fragmenten hiervan met aangehechte ijzerslak en enkele productieslakken met kleine ingesloten fragmenten limoniet wijzen op het gebruik ervan als grondstof.

Van de ijzerproductie op het villaterrein getuigen verder productieslakken en delen van de wolf. Ook het afval van de (na)bewerking van het ijzer is gevonden. Belangrijke conclusie van het onderzoek is dat de ijzerproductie waarschijnlijk heeft plaatsgevonden ten behoeve van de bouw van het badhuis in fase 2 van de villa. Naast de kunde die nodig is voor de productie van ijzer, veronderstellen de kwaliteit, omvang en uniformiteit van de smeedslakken dat voor deze verbouwing van de villa gespecialiseerde vakmensen zijn ingehuurd.

The economic importance of iron smelting and blacksmithing at the medieval castles of Feinfeld and Sachsendorf, Lower Austria.
Finds and features related to bloomery smelting and blacksmithing have been excavated at the castles of Feinfeld and Sachsendorf (Horn district, Lower Austria). The archaeological evidence in both castles consists of roasting hearths and finds of iron ore, slag and parts of ovens and hearths, while in Sachsendorf there are also some iron objects which could be related to blacksmithing. Archaeological and metallurgical research allows us to draw conclusions about the metallurgical working processes. Model calculations show the importance of bloomery smelting and blacksmithing at these medieval castles, but in both cases there was no evidence of excess production to prove trading intention.

Im Jahr 2017 wurden in Sehnde (Region Hannover, Niedersachsen) auf einem archäologischen Fundplatz 32 Rennofenbefunde und 10 Grubenhäuser sowie weitere Befunde entdeckt. Dabei fielen zahlreiche Fragmente als Toneisensteingeoden (TES) auf, die größtenteils aus den Gruben-häusern stammten. Aufgrund ihrer magnetischen Eigenschaften kamen diese Gesteinsfragmente als mögliches Erz infrage. In einem frühgeschichtlichen Kontext sind für Europa TES als Ausgangserze zur Eisengewinnung bisher nur für die Region Sussex/Wealden (GB) bekannt (Paynter 2006). Zur Klärung der Frage, ob TES als Ausgangserz auch für diesen Verhüttungsplatz infrage kommen, wurden geochemische Untersuchungen an verschiedenen archäologischen und rezenten Erzen und Schlacken vorgenommen (Vier Radiokarbondatierungen: ältere RKZ).

Lecture presented by János Gömöri for the “7th International Scientific Conference on Medieval Archaeology of the Institute of Archaeology (Zagreb) titled Secrets of iron - from the raw material to an iron object”. Videofilm made by the Soproni Múzeum, Hungary, 10. 09. 2020. In the first part the Speaker summarizes the main results of his excavations between 1971 and 2006. He highlights the important iron production in Pannonia during the Avar period (7th-9th centuries) and in the early Hungarian era (10th-12th centuries),

Vasolvasztó bucakemencék ásatásai Magyarországon Gömöri János előadása a „Középkori Régészet 7. Nemzetközi Tudományos Konferenciáján”, amelyet a zágrábi Régészeti Intézet „A vas titkai -- a nyersanyagtól a kész vastárgyig” címmel rendezett. A videofilm a Soproni Múzeumban, Magyarországon készült 2020. szeptember 10-én. Az I. részben az előadó röviden ismerteti az 1971 és 2006 közötti ásatásai eredményeit, kiemelve a pannóniai avar kori (7-9. századi) és korai magyar (10-12. századi) vaskohászat lelőhelyeit.

The innovation of iron production is one of the major technological developments in history. The ability to transform certain ‘stones’ into objects of nearly any shape had an enormous influence on the economic and social development of early societies.

Within the last decade, a great deal of research has been done in Central Europe to work out the dating of the first production sites more precisely and to learn more about the technology and the social embeddedness of iron production. Our DFG-funded research in the Teltow region south of Berlin is one example for these activities. It has made it possible to push the date of the earliest iron production activities in Northern Germany back more than four centuries.

Consequently, the idea arose to gather the major experts in the field of Central European early iron production to exchange and discuss these results. We were very happy that 21 of our colleagues accepted our invitation and took part in the conference held in Berlin from the 19th to the 21st of October 2017. Many of them also submitted a paper for inclusion in this volume, which thus provides a very up-to-date overview of the state of research in many regions within Central Europe.

An experiment with the Pre-Roman Iron Age bloomery furnace type “Glienick” took place for the fourth time in the Museumsdorf Düppel in Berlin. In a 13.5 hour smelting process 14.1 kg iron bloom were produced from 57.1 kg of bog iron ore. By reducing the amount of the burnt charcoal it was possible to enhance the efficiency of the process. The smelting residues show similarities to those found on the archaeological excavations.

Experiments have been carried out for determining the archaeomagnetic ages of several baked clay structures from Sopron and its environment. The archaeomagnetic dates are in agreement with the archae­ological ages as shown in Table 1.

В работе сделана попытка определения археомагнитного возраста образцов из обож­ женной глины, два из которых были римского возраста, а пять-относились к раннему венгерскому средневековью. Объекты были извлечены из раскопок в Шопроне и его окрест­ ностях. Результаты представлены в таблице 1.

Sopronból az Árpád-kori ispáni vár kiégett fa-földsáncának, illetve Sopron közelében levő lelőhelyekről két római-kori és öt Árpád-kori égett agyag-objektum (vasolvasztó kohók és ércpörkölő tűzhely) archeomágneses korának meghatározására tettünk kísérletet. Az eredményeket az 1. táblázat tartalmazza.

A Newsletter of the Working Group on Industrial Archaeology, Veszprém Regional Committee of the Hungarian Academy of Sciences. (in Hungarian). Since 1980, we have assembled a gazetteer of all archaeological sites that have yielded evidence
of workshops, raw materials, by-products and tools of handicraft industries of pre-industrial times and cultures, from the prehistoric periods up to the 18th century.....

Bohinj, the South West part of Slovenia is known of its long history of iron production as well. Ancient Bohinj was part of Norik in Iron age and became also Roman world in the last decade B.C.. In November 15th 2002 the author's monographic book POZABLJENO BOHINJSKO ZLATO (Forgotten Gold of Bohinj) was presented. The book describes 2000 years of iron working in the Bohinj area that used its domestic raw materials exclusively, and yet managed to retain its local character in spite of various cultural and political influences to which it was subjected. His research is continuing (see also www.glow-of-iron.eu) SUMMARY Bohinj, a wonderful valley in the heart of Julian Alps, the South West part of Slovenia is not known only because of its beautiful nature with forests, clean water, well known lake of glacial origin and waterfalls, but it is interesting because of its long history of iron production as well.