Hello, welcome back to LuxeSci, a podcast to re-ignite your wonder by exploring the science behind luxury items.
This week we are taking inspiration from all the classical art around us and talking about sculpture! I have to say that being in Greece has really increased my appreciation for sculpture. We just spent a day in Delphi and there was some amazing sculpture, including a sphinx. Also, we got to visit friends on Tinos, where there is a marble museum and a strong sculpting tradition.
So today we’re going to talk about the science behind two popular sculpture mediums, marble and bronze.
History of Marble Sculpture
Marble has been used since ancient times for sculpture, particularly for sculptures of the human form because of its ability to absorb light a small distance into the surface before refacting it. This give a soft appearance that can represent human skin and that can be polished.
Pure white marble is most popular for sculpture with the colored marble being popular for architectural design
Parian marble - from the Greek island of Paros - is famous for its use in the Venus de Milo and many other ancient greek sculptures (e.g. Winged victory of Samothrace)
Fine-grained, semi-translucent, pure-white and flawless marble
Main rival in antiquity was Pentelic marble - which is also flawless white but has a faint yellow tint that makes it shine under sunlight. This is due to the quartz in the marble as an accessory mineral. This type of marble was used most notably for the Acropolis and comes from Mt Pentelicus, just outside of Athens. The quarry is now used exclusively for Acropolis restoration projects.
Michelangelo and other Renaissance sculptors used Carrara marble from northern Italy, though this marble has since run out.
Why use marble in sculptures
We already discussed its slight translucency = this evokes a kind of realism
Some types of marble are relatively soft when first quarried so they are easy to work with, refine and polish
Marble is weather resistant except for acid rain and sea water
The fineness of the grain in marble means that finer detail can be sculpted into marble than say to limestone
One more bit of marble history
The island of Tinos has a long history of marble sculpture
The legend is the the Tiniots were taught how to sculpt by Phidias, whose ship was forced to Tinos by strong winds
Phidias - sculptor, painter and architect. His Statue of Zeus at Olympia was one of the Seven Wonders of the Ancient World
The marble on Tinos is dove white and dark Verde (green) and it was Tiniot artists that created the art form as a staple for Cycladic art
Their art was further honed during the Venetian control of the islands between 2017 and 1715
After the Ottoman occupation (where Tiniots where still free to ply their trade as they saw fit) - Tiniot artists helped to create beautiful classic pieces for the new capital in Athens
What is Marble?
According to the University of Auckland - marble is a metamorphic rock formed when limestone is exposed to high temperature and pressures
Metamorphic rock - rocks that is formed when other rocks are subjected to high heat, high pressure, hot mineral-rich fluids or a combination of the three
Limestone is made up of fossil fragments held together with calcite (most common form of natural calcium carbonate) and the high heat and pressure recrystallizes the calcite into a denser rock with equigranular calcite crystals.
Equigranular - consisting of minerals of approximately the same size
There are usually inclusions (do we remember what those are from our jewelry episodes?) that can turn the marble different colors such as minerals, micas, quartz, pyrite, iron oxides and graphite.
Example - iron makes pink marble
An interesting fact about the process that makes marble is that the calcite crystals in limestone are very small. As the metamorphosis process progresses, the crystals grow larger and start forming the interlocking crystals of calcite. This recrystallization process obscure the original fossils and sedimentary structures of the limestone.
In the process, clay minerals in the marble will become mica and more complex silicate structures
Some might also contribute to the formation of gem minerals - which is why you can find gems such as rubies and sapphires in marble veins.
Cool Science
In 2002, Andrea Timoncini et al published research in Science of the Total Environment looking at bacterial communities in outdoor bronze and marble sculptures
They sampled marble and bronze statues in Bologna and Ravenna Italy
Predictably - significant differences were seen between the bacterial communities on bronze and those on marble
Marble - high biodiversity with Cyanobacteria, Proteobacteria and Deinococcus-Thermus
Bronze patinas - low taxa diversity dominated by copper-resistant Proteobacteria
Copper is widely anti-microbial
Seen in green marble as well
Patina - green film formed naturally on copper and bronze by long exposure or surface appearance of something grown beautiful with age or use
Going to do further research to study the impact of the microbes on the stone and on the bronze
Lastly - what is one to do with all the extra marble from the quarrying process? A review published in 2019 in the Journal of Environmental Management suggested using marble waste in concrete
Marble improved the mechanical properties and strength of the concrete
Used instead of aggregate
Optimum rate of marble was 10% of the concrete mix
Glossary
Metamorphic rock - rock formed by other rocks subjected to high temperature or pressure
Calcite - most abundant natural form of calcium carbonate
Epigranular - made of minerals of almost the same size
Patinas - surface of something grown beautiful with age or use
Fun facts
What kind of marble is the Venus de Milo made of? Parian marble
How rubies related to marble - marble can contain rubies and elements in the marble can contribute to ruby formation
What metals can be used to make bronze - copper and tin, arsenic or other metals
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. Check our social media for pictures of the Marble Museum in Tinos and sculptures from around Greece
References
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