sabato 1 agosto 2015

Italian Aes Proto-Monies Part II

Aes Signatum, Ramo Secco bar, complete

A second method of aes rude manufacture that allows for mainly small resultant pieces, was to pour molten metal into water. This method, was simpler than the method previously discussed, but would not produce very large product.  Size and shape of the resultant pieces could be altered by changing metal composition, altering water temperature and by stirring / swirling the water as the metal is introduced.  Other chemicals could also be introduced to the water that could affect the final shape of the aes rudes.  This process was wonderful for making "small change".  Pieces made by this technique are globular in format, with rounded edges and abstract protrusions.  This process was used in the creation of aes rude, but was not as common as breaking parts from cast ingots, despite the simplicity of the process.  The main reason for this was the small size of the pieces made by this process.  These pieces are a rather unusual find today.  Chemical composition of the bronze really affects the shape. Silver and gold poured in this way produce perfect round pellets and are used today as "casting grain" by jewelers.

Aes rudes formed by broken laminations of  quadrilateral bars.
Corner of Aes Signatum currency bar separated by a split lamination.
A third form of aes rude was derived from faulty casting of quadrilateral bars and rectangular ingots, such as ramo secco bars.  These pieces resulted from hot metal being cast into cold molds, along with brief interruptions in pouring of the metal.  Metal flows into the cold mold and freezes almost instantly on contact with the cold walls of the mold.  Further hot metal flows in and engulfs the edges of the now frozen metal. The flow pattern forms a loose mechanical  grip around the edges of the frozen mass, or it can just abut against it, forming none at all. This forms what is known as a lamination. When the mold is opened, one or more pieces are recovered, all of which have trade value.  In handling, over time, the bonded pieces often came apart with little applied force.  Instant fragments are realized of varying size.  Later, aes grave coins commonly suffered from this phenomenon, usually around the thinner, quicker cooling perimeter of the coin.  A high percentage of aes graves show edge voids, either caused by this process or from trapped air bubbles in non-vented molds.  (I have never found evidence of mold venting on an authentic aes grave. I have seen it on fakes.) Lamination lines and streaks are often evident in bars and coins, once again, usually in thinner, quicker cooling regions.
Quadrilateral bar (aes formatum)  without ornament, parted by lamination break.

For transactions requiring larger volumes of bronze than found in aes rudes, ingots and bars of varying weight standards were cast, with or without ornamentation.  The earliest bars were no doubt void of ornament.  These would be termed aes formatum, and bars with designs, called aes signatum.  The first design commonly used on ingots was that of a dry branch, or ramo secco.  These designs, along with fish spine / rib patterns bisected the bars and gave roughly similar divisions along the length. Often, the patterns on these bars are only faintly evident, due to low relief of the design on the master pattern used.  Many ramo secco bars have very poor relief, and are almost unrecognizable as such.
End shinkage on bronze ingot.
End shrinkage on Ramo Secco bar.

These early aes signatum were often extremely thick, and had varying edge profiles.  A very common attribute of these castings is shrinkage in the center of the end of the ingot that faced the open atmosphere where the ingot was poured. These pieces give visual evidence that they were not made in closed molds like later aes signatum currency bars.  These appear to have been poured into an open-ended vertical mold without any sprue from which to draw metal as the casting cooled and shrank.  The molten metal would cool, and shrink in the process, and the area of least resistance  from which the metal could be drawn would be that exposed to the atmosphere, whose surface tension was less than the surface tension on the walls of the mold. The ambient air pressure would allow the metal to shrink inwardly into the body of the casting. These ingots, like aes rudes, were no doubt made in small, private foundries throughout Italy, and not under governmental control in true mints.  Aes signatum currency bars contemporary with aes grave cast coinage show a much higher grade of execution of both design and manufacture, more suitable to production from a government controlled mint.
Aes Formatum bronze tear drop ornament

Aes Formatum bronze shell.

Aes Formatum bronze astragolos

The final category of pre-monetary bronze artifacts used in trade were the bronze castings of artistic or functional nature.  These today are called aes formatum, along with previously discussed cast ingots and bars.  Any cast ornamental bronze item that could be traded as a proto-money fits here.  Cast shells, tear drops, astragoli, miniature cast figures such as dieties, phallic symbols, axe heads, hammer heads, etc. were all traded for their intrinsic bronze value.  They can all truly be called aes formatum.  Items made of other metals such as iron, lead, silver and gold were also used in barter, and are also true proto-monies, but the term "aes" means bronze in Latin, and solely refers to items cast from it.

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