Investigation of mummies over the years has shown that techniques and the level of skill changed during the period mummification was practiced - from about 2800 BC until the Arab invasion of about AD 640. The technique was at its most successful around 1000 BC, when the High Priests of Amon (king of the gods) were all-powerful - at the time Solomon and David were on the throne of Israel.
The process took 70 days, as described by Herodotus, the Greek historian, writing about 450 BC. There were, he says, three qualities and three prices. In the most expensive, the brain was extracted through the nostrils, and the contents of the trunk, usually with the exception of the heart, were removed through an incision made in the side with a flint knife. Then the body was dried out. In the less expensive method, the internal organs were not removed, instead cedar oil was injected into the body before drying. In the cheapest method the body was just dried.
Herodotus was writing at a time when the skill was on the decline. In earlier periods, in general, the internal organs and brain were removed and the body was packed with material that included sawdust, linen and mud. At the peak of the technique, packing was also inserted under the skin through small incisions.
Drying out took about 40 days, the body being covered with dry natron - a naturally occurring salt compound similar to washing soda. The remaining time was used for anointing with oil, adornment, bandaging and religious rites. The outer bandages were impregnated with beeswax and glued with gelatin.
The internal organs were also dried out in natron before being stored in four sealed vases, the canopic jars, near the body. But at one period, the organs were parceled up and used as part of the body packing.
The wrapped mummy was given a face and chest mask made of cartonage which consisted of linen and plaster. This might be gilded and have inlaid eyes and eyebrows. It was sometimes placed in a wooden case shaped to the body, then in a rectangular wooden coffin, and finally in an outer coffin, or sarcophagus, frequently made of stone. Decoration on the coffins included ritual verses to guard the spirit on its journey.