Most science historians are too embarassed to explain the pagan beliefs at the heart of alchemy. They seem ridiculous to modern readers. Nevertheless, alchemists were not simply a group of people lusting after gold as they are usually portrayed. The transformation of metals into a perfect form, gold, was central to the religious philosophy underpinning alchemy. Alchemists believed that they could know God by studying these chemical changes found in nature. They were inspired by ancient Egyptian cosmology. When alchemy began, people already had a sense that their world was in decline, so they looked back to ancient Egypt for knowledge.In ancient Egypt, farming was the primary occupation, and people believed in a biological model of the universe. They thought the earth was alive and part of a nature goddess who enveloped the universe. The interior of the earth, inside caves and mines for example, was her womb, literally, and therefore sacred. Crystals and gems found inside mines were considered to be "alive" and growing continuously. If gold, for example, were removed from a mine, people believed it would grow back (although the time frame is never specified). In alchemical theory, growing a crystal required heat and "celestial waters" sort of like growing a plant. More important, it required a "pneuma," a supernatural force or energy from the Earth Goddess herself. This pneuma might be created by the moonlight, or a particular alignment of the stars and the planets.
Books on alchemy rarely explain why distillation is central in alchemical experiments. Alchemists used the distillation chamber or "still" to duplicate what they thought was taking place underground in the mines where gold or gems form. The still was called the "womb" after the goddess. Inside its chamber, they hoped to create conditions like those deep inside the earth, but on a much smaller scale! Heat was supplied by a furnace under the still. A gold-copper "seed" was placed inside where it was then exposed to the "celestial waters" (distilled liquids dripping down from the roof of the still). The roof of the still was some distance from the heated materials. Vapors rising upwards would cool and condense into liquid droplets at the top. This distilled liquid would then run down the sides of the chamber into "arms" (metal tubes) for collection to be used possibly later.
When alchemists put acids on the metals, gases would be released. If several kinds of gas were given off, they would mix and form new substances. The alchemists would then collect these substances when they condensed into droplets. In this way, alchemists in the middle-ages discovered how to make alcohol. Alchemists in the early middle-ages recorded as many as 80 pieces of equipment used in their work. Beakers, flasks, jars, pestles, mortars, filters, strainers, ladles, stirring rods, crucibles, dishes, water baths, lamps, furnaces, dungbeds, ash baths, reverberatory furnaces, scorifying pans, and sublimatories were used as alchemical laboratory equipment as early as the 10th century. Mary the Jewess is credited with inventing the Bain Marie. This device acts like a double boiler used in modern day cooking. It allows the alchemist or chef to heat a substance slowly without burning it.
Alchemists did successfully "double gold" by mixing it with copper. They considered the gold-copper alloy to be gold, but gold of a lesser quality. Anything gold or yellow color was thought to be chemically related to gold. Even egg yolks were used in alchemical experiments. When a gold-copper seed was treated by the alchemist with substances like mercury, the metal would change from gold color to black. (Mercury is absorbed by the copper). This was called "Maria's black" after Mary the Jewess. By changing its color, alchemists believed they had reduced the gold back to a more primary state or lower form. The Egyptian word for black is "khem," and it is the root of the words "alchemy" and "chemistry." Once the seed was reduced to its black state, then the alchemists continued to expose it to a variety of distilled substances. Some alchemical procedures involved more than 600 distillations!