Gaius_Cornelius
Tiro
Offline
I love YaBB 1G - SP1!
Posts: 30
United Kingdom
Gender:
|
As mentioned before, plaster-of-Paris does work well as a mould for lead.
It should be easy to make a mould using the lost wax method. Make one or more glandes in wax. Beeswax is easier but given the simplicity of the shape paraffin wax (from a candle) may do. Warm wax is easy to shape by hand. To the basic almond shape, add a cone that will form the pouring hole.
Make up some plaster and half fill a suitable container such as a plastic butter/margarine package. Take care to avoid bubbles. Push the wax master glades halfway into the plaster such that exactly half the cone is in the plaster and the pouring hole will be near one side of the mould. As the plaster sets, make two holes in the wet plaster at either end of the mould, these should be in the shape of truncated cones and will eventually form locating lugs. When the plaster is set, put a thin layer of oil over the surface of the plaster and then fill to the top with liquid plaster and allow the whole thing to set. When set, remove from plastic container and allow to dry slowly.
Because of the layer of oil, the two halves of the mould should separate easily and the wax can be removed by gentle heating. Of course, be aware that both oil and wax will smoke when heated and are highly flammable. Open up the pouring hole (or holes) by removing plaster as required.
You will have a two-part mould complete with locating lugs and pouring hole.
I think I am right in recalling that symbols and letters are excised on glandes (that is to say they stand out on the surface as opposed to be inscribed). This would certainly suggest that the moulds were inscribed, so now is the time to scratch you design into the mould.
Make sure that your mould is completely dry; clamp the two halves securely together and pre-warm it to 100 C or so. Molten lead can be poured in. The mould will be imperfect, so air should not have any difficulty escaping. You will be left with a certain amount of flash that can be removed with a good knife.
Presumably, moulds from antiquity would have been clay that would have been fired. These could have been formed around a master that might itself have been made of some quite hard material - such as lead! I don't know if any remains of ancient glandes moulds have ever been found. If the ancients used masters made from a soft material such as wax, it occurs to me that the almond shape might have had as much to do with ease of manufacture as actual performance as a missile.
|