Metal molds were used cold and conduct heat quickly causing rapidly cool the molten metal. This four and a half minute YouTube video shows metal toy soldiers being cast in modern rubber molds. They tend to have a poorer seal between the mold halves requiring extra work to remove mold seams and sprue points They have fairly smooth surfaces and can capture finer details than sand molds without sand grain impressions on the final surfaces. Older permanent molds were made of metal, while newer ones are sometimes made of other materials including rubber. Patina can mask the surfaces of a bronze coin, and most clay more counterfeits are missed because of this. Few ancient coins are ever identified as ancient clay mold counterfeits, yet the number of molds found shows they were made in large numbers. This three and a half minute YouTube video shows a simply clay mold casting, differing slightly from how a coin would be cast as the object copied here slides easily out of the mold while a mold for a coin requires the mold cut to remove the coin, then rejoined leaving a joint during casting.Ĭlay mold casting was used by ancient Greeks and Romans counterfeiters and thousands of broken terracotta coin molds have been found across the Mediterranean basin. While more labor intensive than sand casting and capturing more details, it shares some of the problems with sand casts. As the clay is lightly fired in the process it usually cannot be reused.
A difference is that the mold halves will stick together must be broken to remove the casting. They are widely used to make fakes to be sold into the tourist market where the buyer has no experience with what a genuine ancient coin would look like.Ĭlay mold casting is closely related to sand casting but uses the much finer medium of clay which can capture finer details. Once invented in China, nearly all Chinese coins from the 6th to 19th century are sand cast, and the Chinese become masters at it.īecause of all the limitations, sand cast are never used to make forgeries intended to fool knowledgeable collectors and dealers. Sand casting was an invented of the Sui Dynasty in the 6th century AD China and was not known to the ancient people in the Mediterranean region which is why a sand cast Roman or Greek coin will always be a modern fake. Even worn ancient coins preserve some sharpness in protected areas, but sand castings have over all weak details. Even very fine sand is too course to capture the very fine details of a coin, so sand cast fakes have relatively poor details when compared to genuine ancient coins. The size of the sand grains varies so you may need magnification to see them, but their presence is the best indicator of sand casting. The texture of sand grains will usually be replicated on the fake's surface, as seen on this sand cast Balbinus sestertius. Before condemning a coin for a marks or an edge seam one must be certain that is not normal for that exact type. Roman Republican Aes Grave are cast rather than struck so nearly always have a casting seam, and some later Republican bronzes struck on cast flans commonly have one. Most ancient coins were struck on cast flans and while casting seams on them seldom go around the edge of the final coins, and are usually obliterated in striking, there are exceptions. There are types of genuine ancient coins with filed edges due to their flan production methods, with Ptolemaic bronzes the most commonly encountered. Some forgers will further smooth the edge and may "worry" it to hide file marks, but will never make it look like the natural edge of a genuine ancient coin. Here we see a filed edge where a casting seam or sprue were removed from this coin. A sprue which filled the sprue channel will be attached and must be cut off. Together these are known as casting seams and may go part or all the way around casting. Metal may also leak into the joint creating a different type of ridge known as a flashing. The joint between the mold halves is normally not perfect, leaving an impression of the joint often as a slight ridge around the edge of the casting. There are several characteristics objects made in sand molds will exhibit. This nine minute video shows a ring copied by the sand cast method, although the video say it is a clay mold process it appears a sand clay mix was used so I consider this sand casting. The coin is removed and a sprue channel is created through which molten metal can be introduced.
The bottom of the coin is impressed in one part, a spacer placed allowing the parts to be separated, then the top of the coin is impressed into the top part of the mold. Sand casts are generally poor quality castings intended only for the tourist market as even novice collectors can learn to easily spot them.Ī mold is constructed in two parts using sand combined with binding agent. Cast Forgeries Sand and Clay Mold Castings
0 kommentar(er)
