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Natural Materials

February 3, 2020

It's interesting how the Ages of Man are defined by the materials used in those times. We have the Stone Age in which stone was man's principal material during a period of about three million years until the advent of metalworking. Copper was used in the Chalcolithic Age, and this was closely followed by the Bronze Age after the discovery that adding tin to copper produced an alloy of greater strength and hardness. Bronze exists over a range of tin concentrations, but modern bronze generally contains about 10% tin.

Late Bronze Age cup

Late Bronze Age bronze cup in the National Museum, Prague

(Photograph by Kozuch, via Wikimedia Commons.)

The Bronze age was followed by the Iron Age that began in the 12th century BC. While iron is an abundant element, it's hard to separate from its compounds, and the melting point of iron, 1,538 °C (2,800 °F) is much higher than that of copper, 1,085 °C (1,985 °F). The Iron Age is the last Age defined by archaeologists, and we still use a lot of iron, today. However, the present day could be considered to be the Concrete Age for reasons I explained in a previous article (Roman Concrete, August 7, 2017).

All technologies develop from the simple to the complex, an example being the evolution of aviation from the Wright Brothers' aircraft to the Lockheed Martin F-35, and man's use of materials shows this trend. Stone, of course, is quite abundant, and stone of desired properties for stone knives and spear heads can be found at your feet. Gold and silver can be found as free metal in mineral deposits, so these were the first useful metals. Archaeologists, however, don't have a Gold Age or a Silver Age in their chronology.

Hesiod, Works and Days, lines 176-178 (Greek)

The seventh or eighth century BC Greek poet, Hesiod, wrote about the ages of man in his "Works and Days." This was a short, 800 line poem, written to his brother as a guide to how he should live his life. Hesiod included a Golden Age and a Silver age in his Five Ages of Man, and he believed that the progression of ages from gold to iron indicated a decline of civilization. This fragment from the Works and Days is translated, "For now truly is a race of iron, and men never rest from labor and sorrow by day, and from perishing by night; and the gods shall lay sore trouble upon them." [Hesiod, Works and Days, ll. 176-178]. (Via Project Perseus))

The expression, "cheap as dirt," might be considered an oxymoron, today, when a pound of potting soil might cost a dollar. However, clay has been used for making pottery, for making bricks, as a building material, and for writing tablets for sixteen or more centuries. Clays are hydrated phyllosilicate minerals that are plastic when mixed with water, but are firm upon drying and hard when fired in a kiln. One modern use of clay is as a coating for paper to produce gloss.

Metals come to us from nature in mineral ores, but another mineral source for modern materials is mineral oil, the generic term for petroleum distillates. The principal non-fuel product of petroleum is plastic, and plastic is such a versatile material that it's a major pollutant, especially as a source of ocean pollution. Plastic decomposes very slowly in the environment, but this decomposition is aided by the addition of materials such as starch or a protein derivative of soybeans that produces a biodegradable plastic.

Ford's 1941 'soybean car'

Ford exhibited a "Soybean Car" (centered in this image) in 1941 at a time when steel was expected to become in short supply because of World War II.

The body was the only component containing soy, and it needed to be about a quarter of an inch thick to exhibit sufficient strength.

This concept car was never developed. (Still image from a YouTube video by Aleksei Germanovich.)

As a consequence of many online videos of dipping things into liquid nitrogen and smashing them to bits, it's common knowledge that most materials become brittle when cooled to very low temperatures. Gaskets are needed for many low temperature mechanical systems, such as liquefaction plants for producing liquid helium. Fortunately, leather maintains its flexibility at low temperatures, so it's often used in such applications. The principal component of leather is collagen, a material having amino acids that combine to form triple helical fibers.

Discarded portions of some food products are also useful materials. Nutshells, especially walnut shells, are used as a sandblasting abrasive in many applications since they are abrasive, but soft enough to not cause damage to the polished piece. They are also non-toxic, they don't produce mineral dust, and they are biodegradable. Pulverized apricot pits are used as an abrasive for deflashing plastic integrated circuit packages.

Apricot halves

Apricot halves, showing the pit. Turkey is the foremost apricot producing country in the world. Its 2017 annual production was 985,000 metric tons, which is nearly 25% of the world's production. This far outstrips the United States 2017 annual production of 37,790 metric tons. (Modified Wikimedia Commons image by Maksim.)

Ford, the innovator of the Soybean Car, has been using other natural materials, such as tree cellulose, in its products. In a recent innovation, it's putting coffee bean chaff, the coffee bean skin that's a by-product of the coffee bean roasting process, into the plastic material from which headlamp housings are made. Ford has partnered with fast food giant, McDonald's, which doesn't roast its own bean but has asked its contract coffee bean roasters to work with Ford.[1-4]

One motivation for incorporating natural materials into products is consumer desire for reducing carbon emission and plastic pollution, and Ford has been using waste from wheat, tomato, coconut, and other plants to satisfy its material needs.[1] Ford headlamp housing are made with talc addition to plastic, but using coffee bean chaff instead of talc allows substitution of a renewable material for a mineral.[1] Coffee chaff is widely available, so Ford decided to try using this waste material, since it's been experimenting with organic materials for quite some time.[1]

Ford teamed with McDonald's since the fast food company generates 62 million pounds of coffee bean chaff annually in the contiguous United States, with a portion presently becoming garden mulch.[3] Coffee bean chaff is quite heat-resistant, and it allows fabrication of parts that are 20% lighter.[2-3] The Ford process involves a first step in which the chaff is heated to high temperature in a low oxygen environment. Using the chaff requires 25% less energy during the molding process.[2-3]

Laboratory sample of coffee bean chaff, and a headlamp assembly containing this material

Laboratory sample of coffee bean chaff, and a headlamp housings containing this material. (Still images from a Ford YouTube video.[4])

As a side benefit, the chaff-plastic composite material smells like coffee during melting, a nice alternative to the typical odors involved in plastic molding.[2] While the headlamp housings are its first coffee bean chaff material, Ford intends to use it for other components, also.[2]


  1. Danielle Wiener-Bronner, "Ford is turning McDonald's coffee waste into headlights," CNN, December 4, 2019. Also at The Pittsburgh Post-Gazette, December 7, 2019.
  2. Chris Bruce, "Ford Is Turning McDonald's Coffee Waste Into Car Parts," Motor 1, , December 4, 2019.
  3. Mariella Moon, "Ford will turn McDonald's used coffee bean husks into car parts," Engadget, December 4, 2019.
  4. Ford and McDonald’s: Executives In Cars Talking Coffee, Ford Motor Company YouTube Video, December 4, 2019.

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