Be Inspired: Materials Under the Microscope - Soapstone

While most of Tom Bass Sculpture Studio (TBSSS) students begin their sculpture journey working in the positive – modelling their sculpture in clay or wax, creating a mould, and then casting it in their preferred material – the art of stone carving remains a core part of the pedagogy at the TBSSS. Working in the negative is an entirely different experience. Many of the TBSSS teachers, guest teachers, students (and artists more generally) have different approaches to working with stone: some try to ‘see’ their sculpture within their piece of stone before they begin carving, and others, like TBSSS guest teacher Carol Crawford, ‘discover’ the form of their sculpture organically, through the carving process.

Many different types of stone are used in sculpture – granite, soapstone, limestone, alabaster, and marble, are all good examples. Each stone has its own unique properties. Properties such as hardness, density, weight, natural colour and its luminescence vary wildly from stone to stone. These properties, in turn, affect how sculptors can work with and display the resulting sculpture: how easily the stone can be carved, how long the carving process takes, how the sculpture can be finished, and whether it will be suitable for outdoor (or only indoor) display.

TBSSS runs courses in marble carving (read more about guest master-marble-carver Usama Alnassar here), alabaster carving, limestone carving and soapstone carving. They also stock supplies of each of these stones and sell them to the wider community. In this series of articles, we take a look at each of these materials to shine a light on their unique properties. To begin, we focus in on the softest of all the sculptural stones, soapstone (pictured left).

Many TBSSS students make their sculptural debut at one of our popular 1-day soapstone carving courses – Sculpture in a Day (the next course is scheduled for September – so if you’re interested, keep an eye on the TBSSS website). Why? Because soapstone is just so easy to work with, and so glorious when it’s finished. Known as soapstone because of its characteristic soapy feel, soapstone is one of the most versatile and widely available of all stones, and comes in a variety of different colours (some of these colours shown above). TBSSS mainly stocks orange and turquoise stone (as it is the easiest to source in Australia), black, green, dark blue, and darker red soapstone are all relatively common.

So just why is soapstone so soft? To answer that question, it’s necessary to delve a little into some basic geological chemistry!

Like all stones, soapstone (or steatite) is made up of different combinations of minerals, which is simply another word for a crystal (a solid structure with a regularly ordered pattern) of a particular chemical composition. For example, quartz is the Earth’s most abundantly occurring mineral, and is simply continuously linked units of the chemical compound silicon dioxide (or SiO2). Most of our well-known household crystals are types of quartz: for example, amethyst, citrine and rose quartz. The difference in colour is due to the presence of minor impurities in different quantities, such as iron, manganese and titanium. Quartz is an example of a single, identifiable mineral, and as we all know, it’s quite hard, rating 7 on Moh’s scale of hardness.

The major mineral ingredient in soapstone, however, is talc, or Mg3Si4O10(OH)2, and by contrast, it’s the softest mineral (rating 1on the Moh scale). It is usually found in powdered form, although there’s a rare crystalline form (see below). The name sounds familiar? That’s unsurprising, because when powdered and combined with corn starch, you get baby (or talcum) powder! Its crystal structure is complex, and shown below, alongside examples of crystalline and powdered talc.

But soapstone is a combination of different minerals – not just talc – hence all the different types and colours. The identity of the impurities is not particularly important, because there’s lots of different possibilities. And so soapstone can comprise from as little as 30% talc (making it harder and suitable for architectural purposes) to 80% talc (the kind we use in sculpture, and the kind that feels soapy). And how do all these different minerals get together? The answer is through a complicated geological process called ‘metamorphosis’, in which existing minerals or rocks are transformed into new combinations of minerals.

 But enough chemistry! What is soapstone used for?

Unlike other forms of rock, soapstone can be found all over the world, and can be mined either industrially or by hand (see below). It has a long history, and was carved by Indigenous peoples all over the world (in Africa, Asia and the Americas) to make all sorts of things, from decorative jewellery, to tools, statues, cooking materials, and furniture. In modern times, it is frequently used for architectural purposes, making great benchtops, tiles and decorative fireplaces (due to it being a great insulator). It’s also used to make moulds for casting softer metals (just as ceramic moulds are used for bronze casting).

And of course, it’s used by artists and craftsmen all over the world to make beautiful art! And that’s why the students and teachers love it at TBSSS.

Next time: we work our way up the hardness scale, focusing in on limestone. Stay tuned.

Article written and researched by William Jackson.

Images

In order from top of article:

(1) A TBSSS student carving soapstone.

(2) Raw mined soapstone (steatite) in three differently coloured forms (source: Wikimedia Commons);

(3) L: Karen Alexander teaching during a Sculpture in a Day workshop (source: TBSSS archives); R: Soapstone sculpture: Baby Elephant by TBSSS student Helen Alajajian.

(4) Three different forms of quartz, L: amethyst; C: citrine; R: rose quartz (source: Wikimedia Commons)

(5) Top: the crystal structure of talc (source: Wikipedia); bottom L: crystalline talc; bottom R: powdered talc, or talcum powder (source: Wikimedia commons);

(6) L: carvers hand mining soapstone on Baffin Island, Canada; R: kneeling soapstone statuette of a man with a seated figure of Osiris between his thighs, from the 25th Dynasty of Egypt, displayed at the Petrie Museum of Egyptian Archaeology, London.

(7) Soapstone sculpture by TBSSS student Ian Kennedy.