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
Glossary
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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