Mining and smelting
In ancient Egypt metals were mined in several areas, by open cast as well as by underground mining. Gold and copper were the first ones processed by the early Egyptian metalworkers. Later in the development of Egyptian metallurgy, electrum silver, iron, tin, bronze, lead and platinum were also worked. In addition, traces of nickel, zinc, arsenic, antimony and cobalt have been detected in small amounts in metal artifacts. Metals were also imported by trade or as a tribute from neighboring countries, especially gold and copper, of which great quantities were used.
Melting, casting and plate production
After the local or imported crude metal had been delivered to the storehouses of temples and palaces, it was weighed and registered by the Egyptian temple or palace administration. Before a quantity of metal was dispensed from the storehouses to the metalworkers for further processing, the metal had to be weighed again, to control the stock of metals and to prevent embezzlement.
Melting the metal
The first job which had to be done by the metalworkers in the temple or palace workshops was the melting of the crude metal. Egyptian pictorial and inscriptional sources depict the melting of copper, gold, silver, tin bronze or leaded tin bronze. In Old and Middle kingdom times, the melting of copper or arsenic copper for the production of vessels and tools for daily use was very common. In the course of the Middle Kingdom and in later period's tin bronze and leaded tin bronze were used. Silver and gold served throughout Egyptian history as the basic materials for objects of royal use or for the funerary and temple equipment.
The metal had to be melted because large ingots or other shapes of crude metal, which were customary in the trade , had to be refined or alloyed for casting or split up into smaller portions for further treatment by smiths.
The metal was melted in one or more crucibles using hearths depending on the amount required. The hearths were charcoal- fired. Charcoal was burnt extensively in the eastern desert and the Sinai. Temperatures of about 1000C (1800F)or even more could be achieved if the embers of the charcoal fire were aroused with suitable tools. In Earlier times fans of foliage might have been employed to provide a draught.
In the old and Middle Kingdom Egyptian metalworkers or melters used blowpipes consisting of reeds with clay tips . With blowpipes a strong blast of air could be directed precisely on to the glowing charcoal below the bottom of the crucible.
There is evidence that Middle Kingdom metalworkers used skin bellows, as mentioned in a text written on a coffin , although skin bellows, probably manufactured from the skin of a goat or a gazelle , have not been found in Egyptian depictions. Much more effective than fans, blowpipes or skin bellows were pot , drum or dish bellows . The dishes were of pottery, wood or stone fitted with skin or leather coverings.
Casting
A small limestone casting mould was found in situ beside one of the small hearths at the excavated site.. This mould was not used for producing objects by open –mould casting but to split the molten metal into smaller portions for further treatment by the smiths, who manufactured plates and sheet metal from the small portions. Moulds of this kind are shown on paintings and relieves in private tombs as early as the Old Kingdom where a metalworker is pouring the molten metal into the mould. To protect his hands, the worker used stones or blocks of wood to hold the very hot crucible. Sometimes, while the metal was being poured, another worker tried to hold back any contamination in the crucible.
Plate production
After being melted, refined and divided into portions, the cooled metal was passed to smiths or blacksmiths for plate or sheet production. Egyptian blacksmiths used very simple tools. The metal was beaten on an anvil made of stone (probably of basalt, diorite or granite) which was placed on a wooden block to absorb the hammering. The metalworkers beat the plates with simple hammer stones without a shaft .Two kinds of hammer stone were in use: one with a flat face and the other with a rounded one. A flat hammer stone was needed for smoothing the metal. While a rounded one was used for chasing. Smoothing and chasing hammer stones are depicted in private tombs from Old Kingdom times to the Ptolemaic period.
Egyptian metalworkers had mastered the technique for annealing as early as the predynastic Period. In the course of the chasing process the beaten piece of metal become hard and brittle and further treatment of the cold metal could cause it to crack. The piece had therefore to , to be heated or annealed, which caused a rearrangement of the crystalline structure of the metal and made it ductile again.
Gold leaf
The gold beaters used hammer stones to beat the foil, which became thinner in the course of the manufacturing process. Silver and electrum also worked to foil, or the thinnest leaf thickness. Objects of a less rare material were often gilded or silver plated. Gold, silver and electrum foils or leaves could be used to cover wooden furniture, statues, coffins and models of daily life manufactured for funerary equipment. Stone vessels, the walls and doors of temples and objects of base metal were covered with precious metal by wrapping the foil round the edge of the object or by inserting the edges of the foil into grooves cut in the surface of the underlying material.
In New Kingdom times or even earlier, Egyptian metallurgist mastered advanced techniques of gold refining in order to produce very pure gold, free of impurities which would be beaten out of the thinnest gold leaf.
The thinner gold leaf could be stuck to surfaces with an adhesive. For the decoration of wooden or stone objects with gold leaf a ground of gypsum plaster or a similar material was often applied first to the material before the gold leaf was stuck to it. It seems probable that metalworkers only produced the gold leaf while the gilding was done by the workers in wood, stone or wax who manufactured the objects to be gilded.
As described in an Egyptian papyrus of the Roman Period, metal gilders of that time knew the chemical process of fire-gilding with gold amalgam. Gold amalgam was applied to the base - metal object to be gilded. In the course of the fire –gilding process, the mercury content of the gold amalgam vaporized and the gold remained on the surface of the metal objects. As mercury fumes are extremely toxic, fire gilders or those living in the neighborhood of a gilding workshop were always in danger of mercury poisoning.
Reference: Egyptian metalworking and tools by Bernd Scheel