Apr 27 2024

The Reverberatory Furnace and Bronze Casting

Bastian Asmus

 Todays article mostly is on the reverberatory furnace.  However, this is the beginning of a small series of articles that are concerned with casting of larger objects: Cannon, bells and statuary art. Only recently my colleagues and I published an article on the written evidence with regards to the casting of the large bronze statues. Or so we thought; the statues from the Hofkirche in Innsbruck were made from brass  (Mödlinger, Asmus & Ghiara, 2024).

This scheme explains how a reverberatory furnace works. It uses wood as fuel and heats large quantities of metal with the flames only.

A reverberatory furnace hypothesis based on a 16th description (Asmus, in prep)

The beginning of the 16th century is commonly accepted as the end of the middle ages and the beginning of the modern age. This does also apply to the metallurgical trades, because around the same time the reverberatory furnace makes its appearance in Europe. Seemingly out of nowhere, or at least without any apparent predecessors, the reverberatory furnace manifests itself as fully evolved piece of technology in the metal trades. Leonardo da Vinci and Buonaccorso Ghiberti, nephew of the famous Lorenzo Ghiberti left us with sketches of these furnaces. Artists and scholars like Vannoccio Biringuccio (1540) or Benvenuto Cellini (1974, 2005) left us with treatises, where they provide insights into the design and use of these furnaces.

This type of furnace appears more or less suddenly at the beginning of the modern era. There are nor real preceding furnace designs from the middle ages in Europe, so there is a possibility that this concept arrived in Europe as a new concept. The reverberatory furnaces are one key component in the Industrial Revolution (Bulstrode 2023) as puddling furnaces for the making of steel, from scrap iron and also from raw cast iron.

A reverberatory furnace for Vianden

The reverberatory furnace for Vianden is a new reconstruction based on a 16th century treatise of the founding of cannon (Asmus, in prep). The experiment follows the instruction closely and  will  use it to cast a cannon, based on one cannon found at castle Brandenbourg, Luxemburg. It is one of the two cannon made by Casper Bux from Vianden in the 16th century.

An image if the signature of Casper Bux on one the two surviving Bux cannon.

The signature of Casper Bux von Vianden.

The cannon mould will also be made experimentally following a variety of 16th century at the Castle Vianden. The whole process can be seen live at the castle.

A reverberatory furnace not only for cannon

The Vianden  reverberatory furnace is far more than only for cannon casting. With the very same furnace we can cast bells by or the cast of statuary art. As a fully trained bronze caster I do have strong interest also in bronze sculpture, and from the above mentioned Cellini treatise we know that his Perseus with Medusa was made by such with the reverberatory furnace.

To this end I hope that we can use the  Vianden reverberatory many times for the purposes of contributing towards the understanding the intricacies of Renaissance bronze casting and beyond.


Asmus, B. (in prep), A techno-critically edition of Kaspar Brunners Report of gun founding.
Vanoccio Biringuccio (1540) De la Pirotechnia. Siena. Available at: https://digital.sciencehistory.org/works/n888ils (Accessed: 23 September 2023).
Brepohl, E. (ed.) (2005) Benvenuto Cellini. Traktate über die Goldschmiedekunst und die Bildhauerei. Böhlau Verlag.
Bulstrode, J. (2023) ‘Black metallurgists and the making of the industrial revolution’, History and Technology, 39(1), pp. 1–41. Available at: https://doi.org/10.1080/07341512.2023.2220991.
Benvenuto Cellini (1974) Abhandlungen über die Goldschmiedekunst und die Bildhauerei. Translated by Max Fröhlich. Basel.
Mödlinger, M., Asmus, B. and Ghiara, G. (2024) ‘The “Schwarze Mander” of the Court Church in Innsbruck, Austria: Manufacture and Production of Monumental Brass Statues in the Renaissance’, International Journal of Metalcasting [Preprint]. Available at: https://doi.org/10.1007/s40962-024-01299-4.


Apr 20 2024

Renaissance Casting Technology: New Paper out!

Bastian Asmus

A new paper on Renaissance Casting Technology was just published. It looks both, into the chemical composition of the utilised alloys, as well as into the primary sources concerning the manufacture of the cenotaph of Emperor Maximilian I.

Reconstruction of Renaissance casting techniques. This Image of  the calculated wall thickness of the of Theoderic the great, based on the mass of the statue.
For the Reconstruction of Renaissance casting techniques the wall thickness of the of Theoderic the Great was calculated, based on the mass of the statue.

Get the full paper here https://doi.org/10.1007/s40962-024-01299-4

The 28 “Schwarze Mander” (Black Men) are undoubtedly amongst the most magnificent monumental brass statues of the Renaissance. Commissioned by the Holy Roman Emperor Maximilian I for his funeral monument at the beginning of the 16th century, they were completed more than 30 years after the Emperor’s death and are now part of his cenotaph in the Hofkirche in Innsbruck. Revising the original manuscripts and letters exchanged between Maximilian I and the various artists sheds light on the manufacturing process and the challenges the artists encountered whilst producing the statues. Moreover, the alloys used in the manufacture of the statues, now all blackened due to patination processes, were identified through non-invasive chemical analysis of all the statues.


The 28 Schwarze Mander are without a doubt amongst the most stunning brass statues of the Renaissance period. They were commissioned by Maximilian I, the Holy Roman Emperor, for his funeral monument in the early 16th century but took over 30 years to complete after his death. Originally, the emperor wanted 40 statues of ancestors and saints of the Habsburg family and 100 statuettes of other saints associated with the House of Habsburg, as well as a sarcophagus for the emperor himself. In the end, 28 statues (Table 1), 23 statuettes and 34 busts of emperors (of which only 21 have survived) were created. The sarcophagus was replaced by a cenotaph with the kneeling statue of Maximilian I, the four virtues and 24 marble reliefs. Maximilian I, at the end, was buried in Wiener Neustadt.

Get the full article here and finish reading it: https://doi.org/10.1007/s40962-024-01299-4


Mödlinger, M., Asmus, B. and Ghiara, G. (2024) ‘The “Schwarze Mander” of the Court Church in Innsbruck, Austria: Manufacture and Production of Monumental Brass Statues in the Renaissance’, International Journal of Metalcasting [Preprint]. Available at: https://doi.org/10.1007/s40962-024-01299-4.

Sep 29 2021

Danzig handgonne

Bastian Asmus

Wiltu ein puchsn gießn sei sy gros oder klayn – if you want to cast a gun be it big or small

The Danzig handgonne is an unusual very early form of a firearm. The handgonne is unusual because it shows a three-faced representation at the muzzle. It is interpreted by some colleagues as a representation of the Slavic god Triglav .

How old is the handgonne from Danzig?

Unfortunately, the Danzig handgonne cannot be dated precisely because the circumstances of its discovery are unclear. We know the approximate find date: around the 1920s. There are two competing statements with regards to its find location (Petri, 2017, 222):

  1. It is from the area of Schwedt, from a pond on an estate.
  2. It is from near the city of Gdansk, and turned up during dredging operations

The Danzig handgonne was privately owned for a long time, and was auctioned at Christies in 2014. Today it is in the collections of the Royal Armouries in England. Based on stylistic features, the handgonne is believed to have been made between the mid-14th and early 15th centuries AD.

In this video, I show you how I would have cast the Danzig handgonne in the late Middle Ages using the lost wax process. I first modelled an original wax. Then I made a mould out of a refractory material: moulding loam. When the mould is fired, the wax issues from the mould, leaving the mould cavity in the hardened loam. The bronze can be poured into this. For demoulding, I have to break the mould: the mould is now lost, so each casting is unique….

I will also show you how to finish the Danzig handgonne barrel. Burrs have to be removed by chisel, the surface has to be finished in some places with the file and the scraper. Finally, I make the ash stock for hand rifle. It is a simple bar stock, as we know it for example from the Landshut Zeugausinventar.

Which material?

Unfortunately, there are no exact composition analyses of the handgonne available until today. It is definitely a copper alloy, brass is ruled out for the period and region. That leaves copper and tin bronze. Strong copper rich alloys are an unsuitable material, but these were actually used as recent investigations on another firearm show (Asmus & Homann, in prep). In addition, the numerous accounts on the bombards from the Teutonic Order area show that copper was apparently used for gun casting . Still, for this project I chose the safe option and used a 90/10 tin bronze alloy, an alloy often employed for firearms.

As an archaeometallurgist from the Laboratory for Archaeometallurgy, I study the metallurgy of our ancestors. For this I use my craft as an art founder, the historical and archaeological disciplines, as well as the material science disciplines of the natural sciences.