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LuxeSci Show Notes: S2E14 - Metallurgy

Hello, welcome back to LuxeSci, a podcast to re-ignite your wonder by exploring the science behind luxury items.

This week we are talking about a science that is as ancient as humans and has been included in myths and legends for millenia. That is metalsmithing.  I don’t think that the impact of metalsmithing on the human species can be quantified. So much so that there’s a whole are of science devoted to metals (metallurgy).  This is a big topic and we can’t cover all of it in one episode but we will try to get into a little bit of the history and a whole lot of the science.  

So today we’re going to talk about the science behind two popular smithing metals, iron and copper.

History of Metal Smithing

  • So first a definition - a metal smith is a craftsperson who makes useful items our of metals

  • Smithing is one of the oldest metalworking occupations

  • Types of smiths

  • Blacksmith - works with iron and steel

  • Bladesmith - forges knives, swords and blades

  • Brownsmith - works with brass and copper

  • Coinsmith - coins and currency

  • Coppersmith - works only with copper

  • Goldsmith

  • Gunsmith - builds and repairs firearms

  • Armourer

  • Locksmith

  • Tinsmith

  • Whitesmith - works with white metal (tin and pewter)

  • The earliest record of metal employed by human is with gold.  Gold, silver and copper were likely the first metals that were manipulated by humans

  • Small amounts of natural gold has been found in Spanish caves dating to the late Paleothic period (40,000 BC)

  • The first evidence of extractive metallurgy (heating rocks to recover pure metals) has been found at archeological sites in Serbia and dates from the 5th and 6th millennia BC

  • The use of lead seems to predate copper though both are found in the Balkans

  • Dimos’ timeline of metal working

What is a metal?

  • Around 75% of elements on the periodic table are metals - hard define precisely what they are so scientists use a list of characteristics

  • Some characteristics of metals are

  • Conducting electricity 

  • Heating well

  • Strong, shiny and hard

  • Often malleable

  • Types of metals in the periodic table

  • Alkali metals - group 1a of the periodic table - think lithium, sodium, potassium

  • Soft, shiny metals with low melting points

  • Fun fact - these metals react violently with water. The reaction gives off heat and hydrogen and sometimes the heat ignites the hydrogen with explosive results

  • Alkaline earth metals

  • Group 2 on the periodic table - Beryllium, Magnesium, Calcium, etc

  • Silvery-white, shiny metals that are fairly reactive

  • Solid in fire and insoluble in water so early scientists called them “earth”

  • Transition metals - this definition is a little trickier.  Basically, these metals have electrons that can form chemical bonds in two shells instead of one. 

  • Most are hard, lustrous and have high melting points and boiling points and are good at conducting heat and electricity

  • Titanium, iron, nickel copper

  • Form many useful alloys

  • Rare earth metals - 17 nearly indistinguishable lustrous silvery-white soft heavy metals. Initially thought to be rare but some are not so

  • Also called lanthanides

  • Hear a lot about them now as they are involved in many applications for electric components, lasers, glass, etc

  • Tarnish slowly in air at room temperature and react slowly with water

  • Serve no biological function other some specialized reactions in bacteria

  • Poor metals

  • Semi metals

  • Alloys

  • Combination of a metal with at least one other metal or nonmetal

  • Retains the characteristic of a metal

Cool Science

  • So after all this background, what actually happens when you work with metal?

  • I think one of the most iconic images when we think about metalsmithing is the forge.

  • A forge is a hearth used for metalsmithing

  • Basically it is a place for heating the metal

  • The forge heats the metal to a malleable temperature where it can be manipulated

  • Compressive force is then used to shape the metal

  • This also refines the grain structure of the metal and improves its physical properties

  • Grain structure - crystalline structure of metal where each grain is a distinct crystal with its own orientation

  • Within the grain - individual atoms form a crystalline lattice. In this shape, each atom share loose bonds with its neighbors.  When stress is applied to the metal, the atoms start to spread apart.  The bonds stretch and attractive forces between the atoms will oppose the stress like tiny springs

  • The grain flow can also be oriented in the direction of the principal stress encountered in the use of the object

  • All of these forces have to be managed when working with metal, what is the grain structure of the metal, what is the melting point, what is the impact of different types of forging on the strength of the metal, what will it be used for.  It’s lots of variables to consider to make a metal item.

  • For example - iron changes color as it heats, going from red, to orange, to yellow and then white

  • The optimal temperature for working with iron is when it’s a bright yellow-orange color (forging heat)

  • There is so much to cover with what happens with metals when you heat them, cool them, work with them.  For a really comprehensive take, the Materialism podcast has a great take (Episode 13 is on Blacksmiths)

  • But since this is a podcast about luxury, i thought i would talk a little more about a more luxurious metal.  We’ve already done silver (episode 11), platinum (episode 12) and gold (episode 5) so what other metal can be added to the luxury fold….copper!

  • I think that one luxury item that is most associated with copper is those beautiful copper pots and pans that you see in super nice kitchens but it can also be used to make jewelry, belt buckles and statues (hello Statue of Liberty)

  • Transition metal

  • Now the first step is to get the copper out of the ground. There are two common types of copper ore, copper oxide and copper sulfide. 

  • Hydrometallurgy - extracting copper from copper oxides using water-based solutions at ordinary temperatures

  • Pyrometallurgy - extraction from copper sulfides using heat and physical steps

  • Going back to our conversation on metal grains, copper atoms are irregular in their arrangement so that the metal eventually cracks with the stress. 

  • In order to make copper items, annealing must be used 

  • Annealing - heat treatment

  • Atoms of copper rearrange themselves and migrate to a more regular, crystalline structure

  • Makes the metal softer and more ductile and not as brittle

  • Quenching - rapid cooling in water, oil, polymer, air or other fluids

  • Preserve the new atomic structure of the copper

  • Can reduce the crystal grain size as well leading to increased hardness

  • On a more personal note - i mentioned in a previous episode that i have an allergic contact dermatitis to metals.  While I always thought it was unusual, apparently 10-15% of Americans have a similar allergy.  What it means for me is that if I wear a metal that is not gold, I will develop hives.

  • ACD is driven by T cells, members of your immune system with a wide diversity of jobs. 

  • Classified as a delayed-type hypersensitivity response - respond after 48-72 hours after exposure

  • Pathway - metal ions bind to dendritic cells (circulating immune cells that are on the look out for foreigners).  This activates the cells to migrate to dermal lymph nodes where they encounter the T cells, active them and the T cells move to the bloodstream.

  • The exact players that are responsible for the itchy rash are not yet completely known but it is likely that proteins secreted by the immune cells are involved with the reaction that I (and others) experience


  • Metal - solid material that is hard, shiny, malleable, fusible, and ductile with good electrical and thermal conductivity

  • Alloy - mixture made by combining two or more elements, one of which is a metal and that has metallic properties. Usually done to give greater strength or resistance to corrosion

  • Grain structure - arrangement of differently oriented crystals

  • Forging heat - best heat to work with a metal

  • Dendritic cell - immune cell found in tissues that boosts immune responses by foreign proteins (antigens) on its surface to other immune cells

  • T cell - usually in the lymph nodes and contain receptors to recognize antigens and retain memory of antigens they have seen

Fun facts

  • 75% of the elements on earth are metals

  • Rare earth metals serve almost no biological purpose

Thank you for listening to this episode of LuxeSci.  Please tell at least two people about this podcast.  This is the best way to help us get noticed and find new listeners.  A special thanks as always to my audio engineer Dimos.  Our theme music is Harlequin Mood by Burdy.  

As always, find us all over social media at LuxeScipod for fun facts, vocab words and more!  And please drop us a note, we love to know who is listening.



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