Dear All,
I am going to finish my Forbes Fellowship at the Department of Conservation and Scientific Research in Freer Gallery of Art / Sackler Gallery of Art, Smithsonian Institution in Washington DC. I will stay for a month in Beijing and then, to be in Technical University of Berlin couple of months, where I will study the metallurgy in later ancient China based on the achives names zeli. Please contack me with following address:
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Thank you
Rongyu SU
Prof., Institute for History of Natural History
Ahinese Academy of Sciences
137 Chaonei St., Beijing 100010
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>>> [log in to unmask] 09/25/01 04:34PM >>>
Matthijs van Nie wrote:
>As to vents: It's hard to imagine that a thin wheellike piece with a
>diameter of six cm an inner circle of some 2-3 cm and the connecting
>"spokes" can be cast without vents in a two-piece mould.
I wouldn t, as I said, hesitate to cast an object like this without using air vents in the mould. According to my experience it would work splendidly, although I would of course feel a lot more safe to make a perfect pour in a ventilated mould.
The thing is, that in a well preheated mould (for an object like this, maybe between 500-700 degrees C) the present air in the cavity will be just as hot as the mould itself - which would mean rather expanded and thin air, meaning not very much air at all present in the end. If I m sure I use a well prefired mould that doesn t emit any mould gases, and a first class alloy which doesn t produce any larger volumes of metal gases, the air/gas problem will be a minor one and I could safely cast an object like this without vents in the mould.
>Anders, is there, apart from the risk the object won't fuse properly, any
>other reason open moulds are not likely for thin objects? I can imagine
>that if the mould is heated to a certain temperature this won't be a
>problem. [giving at the same time perhaps the answer to the question why
>one side is complete blackened and the other is not .... ]
I m sceptic. This is a complex object with a lot of thin details which would be very hard to properly fill with metal. Add to this the fact that the cast object would look very poor and need a l o t of afterwork.
An important and essential point in casting, is that if done properly, it provides opportunities for producing almost perfect objects directly from the mould, and that this is very very easily done (it s almost magical...). As the Bronze Age smiths for sure knew these methods, it would be against common sense to suggest that they actually cast poor semi-manufactures that needed hours and hours of afterwork, when it would be easier to get the finished object directly out of the mould (and this is an important quality in the essence of metal casting).
I simply do not believe in the idea of casting a pin like this in an open mould.
Anders Söderberg
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