Nov 14 2017

Non-ferrous sheet metal

Bastian Asmus
Non-ferrous sheet metal: red brass, 0,35 mm

Non- ferrous sheet metal: Custom made historic red brass alloy,

Non-ferrous sheet metal

Who is not familiar with this, you want to make an object from non-ferrous metal sheet of a certain alloy, e. g. a helmet of the Urnfield period. But try as you might no sheet metal of the desired alloy can be obtained in the industry. The industry is simply not interested in supplying small and micro-enterprises or cultural science research projects. But that is no longer the case, as the Archaeometallurgy Laboratory has acquired a medium-sized rolling stand, where sheets up to a maximum theoretical size of 500 mm width can be rolled, though in reality a width of 450 mm is more likely to succeed. This is done in a purely hand-crafted process and thus comes close to the requirements of archaeometallurgical research.

Red brass slabs for sheet metal makingCast red brass slabs, ready for heat treatment

The Laboratory for Archaeometallurgy deals with the reconstruction of past production techniques, i. e. the rolling of non-ferrous metals. For about a year now, the laboratory has been working on the production of sheet metal for the production of brass instruments, producing historical sheet metal alloys, casting them into slabs and processing them into sheet metal.

To this end, we have acquired a larger duo rolling stand with which we can manufacture sheet metal in special alloys by hand, which are no longer commercially available. This is of particular interest for the manufacture of instruments as well as for the production of countless archaeological and prehistoric metal sheet finds such as belts, situles, armour, helmets or shields. We are excites about this, because now we are no longer bound to the small selection of bronze sheets that are commercially available and yet already difficult to obtain.  For the reconstruction of prehistoric and historic objects we can now produce the sheet metal that is required!.

The short film provides a glimpse of the trials and errors that are necessary when making historic non-ferrous sheet metal. By far not every metal alloy behaves in the same manner, some do not like being cast, some do not like being cold rolled. Others yet can only be rolled hot or have to be worked first with a hammer. It is an ongoing enterprise to make historic and prehistoric sheet metal, and a fascinating one, too. Turning a cast object into malleable sheet metal is something that a bronze founder does not do every day. In all cases the slabs and sheet metal to be has to undergo repeated heat treatment in order to produce good quality sheet metal. A process that is monitored by our lab by means of metallography…

 

 


Oct 25 2017

Short documentary – favourite tool of a tap maker

Bastian Asmus


A conical reamer for the tap maker

In Nuremberg the tap makers belonged to the redsmiths. This article is about a simple question of how the conical opening of a late medieval tap was dressed. Although you can do this completely manually, as I have shown in the short documentary, it is highly unlikely that it was actually done this way by the Nuremberg Red smiths or tap makers. Grinding the stop cocks into the tap takes several hours, even if the casts had a good fit to  begin with. Of course, it is not the spent labour time that has caused me to investigate the grinding of the stop cocks in more detail, it was rather the pictorial evidence that I found in Weigels book of trades and in the Nürnberger Hausbücher of the Zwölfbrüderstiftung.

Tap maker Hans Zeuller

Redsmith and tap maker Hans Zeuller

Redsmith Hans Zeuller with conus reamer. Source: Wikimedia Commons

The tool with which Hans Zeuller uses is clearly visible inside of the tap We can assume that it is a kind of conical reamer; i. e. a tool used in a scraping rather than a cutting fashion. Metals are very dense and can hardly be cut by hand. Continue reading


Oct 6 2017

Film: How to make a 15th century beer tap

Bastian Asmus


Reconstruction: Functional tap from the early 15th century. Reconstruction: Early 15th century tap. The location is Zurich, Switzerland.

Some time ago I made a tap for a re-enactment brewer. I was already able to gain experience with the production of tap taps when I made my Aquamaniles. Therefore I decided to document the manufacturing process. Medieval taps often have a stylized cocks as a handle on the plug.  From the end of the Middle Ages taps or spigozs were made by the Zapfenmacher. One of the centres was Nuremberg. In the iamges of the Mendelsche and Landauersche Hausbücher of the Zwölfbrüderstiftungen it is interesting to note that the process step for the production of the taps shows only the reworking, but never the moulding. The illustration of the redsmith by Jost Amann in Hans Sachs book of trades gives at least a hint of the moulding material..

In the background, lumps of clay may have served as a raw material for the moulding material.

A little later again, in the 17th century, Christoph Weigel depicts the Zapfenmacher in its own right . Here a strong specialisation had taken place within a century.

The films are not about a strict archaeological experiment. Rather, it is a matter of examining some hypotheses on the manufacturing process. First and foremost, these were:

  1. Is it possible to make a wax model where plug and tap fit snugly?
  2. Can you cast this in such a way that there is little rework?
  3. How can the grinding of the plug into the tap be mastered manually?

Have fun watching. As always, I am looking forward to your criticism, questions or suggestions.

The first part deals with the history of the tap and the production of the wax model.

The second part is about moulding the wax model, pouring the tap and the first cleaning after casting.

The third part is about finishing the cast tap. This means that it must be roughed, filed, drilled and ground. The grinding of the plug into the tap’s body was particularly exciting. In fact, absolutely leak-proof tap can be produced with the simplest of means.

 

References

Sachs, H. and Amman, J. (1568) Eygentliche Beschreibung aller Stände auff Erden, : hoher vnd nidriger, geistlicher vnd weltlicher, aller Künsten, handwercken vnd händeln ... / Durch den weitherümpten Hans Sachsen gantz fleissig beschrieben, vnd in teutsche Reimen gefasset, sehr nutzbarlich vnd lustig zu lesen, vnd auch mit künstreichen Figuren, deren gleichen zuvor niemands gesehen, allen Ständen so in diesem Buch begriffen, zu ehren vnd wolgefallen, allen Künstlern aber, als Malern, Goldschmiden, [etc.] zu sonderlichem dienst in Druck verfertigt. [bey G. Raben :
Weigel, C. (1698) Abbildung der gemein-nützlichen Haupt-Stände von denen Regenten und ihren so in Frieden- als Kriegs-Zeiten zugeordneten Bedienten an bisz auf alle Künstler und Handwerker / von Christoph Weigel. Available at: http://gallica.bnf.fr/ark:/12148/btv1b8553025f (Accessed: 31 August 2016).