Ceramic Rock Glazes
As ceramicists, we are bounded by the materiality of our practice. Product of the dramatic development of a consumerist society, our reliance on finite natural resources has produced, over the last two centuries, an inescapable tie with nature. While our practices have significant ecological and societal impacts, it is also our connection with nature that invites us to be conscientious makers, and to pay particular attention to developing sustainable practices in our studios to lessen the burden on the future.
In recent decades, wild/locally-foraged clay has received global recognition in the world of ceramics regarding sustainability. However, other materials have yet to receive serious considerations and, consequently, many remains partially explored – if not almost totally absent from mainstream practices. Among these materials are rocks. It is important to note that rocks themselves have never been absent from ceramics. In fact, almost all materials commonly used in our practice are derivatives of some form/type of rock.
Yet, when it comes to ceramic glaze making, the intense and rapid manufacturing of materials from the mining industries has created a market for readily available and “pure” powders and, as a result, has reduced and discouraged the need to process our own materials, such as rocks. As the depletion of our finite resources continues on a large scale, this exhibition serves as a (re)introduction to this lost art, while exploring both the technical aspect of using unprocessed rocks as the base ingredient in glazes, and the (new) aesthetic possibilities they offer, more precisely for firing occurring at cone 6 oxidation in an electric kiln.
The work presented here examines 15 different rocks processed and tested between June 2023 and August 2024 with various other ingredients. With rocks being part of the equation in developing ecologically friendly practices, it is my hope that this project contributes to the articulation of a (new) geological language of alternative ceramic materials.
A note on the virtual exhibition
Due to the extensive scale of the project, which was initially presented in-person, I have chosen to modify its presentation to suit the webpage format more effectively. Consequently, this virtual version offers only a partial view of what was originally showcased.
Please note that this is a work in progress, and much of the fine-grain details of this exhibition will be published separately. Links to these resources will be added as they become available.
Before we begin
Before individually presenting all the rocks used for this project, I believe it can be useful to know the methodological progression of this work (see attached image). Please, feel free to skip this section if you are more interested in seeing the final pieces.
First, all the rocks were crushed and sieved at different mesh size : one “fine”, the other “coarse”. For a short introduction of the tools used for crushing, you can read my previous publication (rock crushing tools). This step was followed by what we would call a “melt test” (see the hexagonal tiles on the right). Essentially, by putting the rock “raw” in the kiln, I was able to get a first impression about the way the rock behaves at cone 6 (~1220°C).
For example, what is the quality of the melt ? Is it partial, fully melted, or does it not melt at all ? This test also indicated the general colour palette that I could be expecting from that rock, especially if I am using it as the primary ingredient in my glazes. Finally, a melt test can be a great way to confirm some of the hypothesis I had in regard to the minerals inside of the rock. This was also repeated as inclusion in the clay (see the flat rectangular tiles on the right). The 5% added allowed me to get a sense of the way these could work as a “stain” or as “speckles” in the clay body.
Afterward, the “fine” powder was mixed with various commercial fluxes to produce a wider range of colour and texture (see rectangular tiles on the left). The recipe I used for these was 85% of crushed rocks, 10% of flux, and 5% of clay. Finally, the glazes I found most interesting were used on a series of moon jars.
Red Jasper
Code name
É23-A
Potential Minerals
Quartz (Silica)
Calcite (Whiting / Calcium Carbonate)
Pyrite (Iron)
Hematite (Iron)
Lepidolite
Code name
É23-B
Potential Minerals
Lepidolite (Lithium-bearing Mica)
Quartz (Silica)
Calcite (Whiting / Calcium Carbonate)
Greenschist
Code name
É23-C
Potential Minerals
Fuchsite (Chromium-rich Mica)
Chlorite (Iron & Magnesium)
Albite (Sodium)
Pyrite (Iron)
Chrysocolla Quartz
Code name
É23-D
Potential Minerals
Quartz (Silica)
Chrysocolla (Copper)
Calcite (Whiting / Calcium Carbonate)
Amphibolite
Code name
É23-E
Potential Minerals
Biotite (Iron & Potassium)
Muscovite (Potassium)
Plagioclase (Calcium & Sodium)
Chlorite-Quartz Carbonate
Code name
É23-F
Potential Minerals
Quartz (Silica)
Chlorite (Iron & Magnesium)
Calcite (Whiting / Calcium Carbonate)
Quartz
Code name
É23-G
Potential Minerals
Quartz (Silica)
Calcite (Whiting / Calcium Carbonate)
Sulphides
Quartz
Code name
É23-H
Potential Minerals
Quartz (Silica)
Calcite (Whiting / Calcium Carbonate)
Pyrite (Iron)
Biotite Schist
Code name
É23-I
Potential Minerals
Biotite (Iron & Potassium)
Muscovite (Potassium)
Quartz (Silica)
Biotite Schist
Code name
É23-J
Potential Minerals
Biotite (Iron & Potassium)
Muscovite (Potassium)
Quartz (Silica)
Pink Feldspar
Code name
É23-K
Potential Minerals
Quartz (Silica)
Orthoclase (Potassium)
Concrete
Code name
É23-L
Potential Minerals
Sand (Silica)
Lime (Calcium Oxide)
Aggregates (e.g., Sandstone, Granite or Basalt)
Lepidolite
Code name
É23-M
Potential Minerals
Lepidolite (Lithium-bearing Mica)
Muscovite (Potassium)
Quartz (Silica)
Calcite (Whiting / Calcium Carbonate)
Biotite Granite
Code name
É23-N
Potential Minerals
Quartz (Silica)
Biotite (Iron & Potassium)
Plagioclase (Calcium & Sodium)
Green Aventurine
Code name
É23-O
Potential Minerals
Aventurine (Silica)
Muscovite (Potassium)
Calcite (Whiting / Calcium Carbonate)
What’s Next ?
Curiosity.
This is how it all started.
A simple question: “What if I crush this rock and put it into a kiln at 1200° Celsius?”
As I reflect on this project, I find it fascinating how that question completely (re)oriented my ceramic practice. What started with a rather straightforward desire to know has transformed into something completely different. Because curiosity is much more than just a “desire for knowledge”. Curiosity suggests a certain concern. It is not only asking “what is”, but more importantly “what could be”. And so, in this relentlessness to find the familiar strange — to throw off familiar ways of doing things and looking at them in a different way — curiosity becomes an act of care. Therefore, while I truly appreciate the (new) aesthetic possibilities these materials offer, they also remind me of the way they connect to and affect (or affected by) broader societal and ecological issues. Accordingly, there’s a part of me that wishes that this project also inspires hopefulness and activism. In truth, I hope that this exhibition offers a glimpse of hope for the future – that it is, indeed, possible to find alternatives that could (re)orient our practices toward something that can be more ethical and environmentally cautious.
As my reflection comes to an end, I now have to face the inevitable question: what’s next? Earlier, I said that curiosity evoked care. Consequently, when I wonder about the future of my work, I find myself returning to these two questions: “What can I do differently?” and “How can I make a difference?”. For the former: while all the glazes developed for this exhibition were made using various commercially available ingredients (such as fluxes and clay bodies), there are many local materials that could work as alternatives. For instance, clay can be collected/foraged locally, bringing with itself the richness and uniqueness of the soil it was found. Furthermore, there are many alternatives for fluxes that can be found/made/collected locally (e.g., eggshells, seashells, wood/plant ashes). On top of all of this, I am also thinking about the inclusion of other materials that are by-products of other industries (e.g., glass shards or dust, construction bricks, countertop off-cuts, metal sludge/slurry, or concrete). For the second question: I think there is a serious need to make these practices easier to get into. Unfortunately, a lot of the knowledge and expertise regarding rocks and other materials (beside clay) are commonly found in publications that are either out of print, difficult to find, or astronomically expensive to get. Alongside the few artists that are openly sharing their process, I would love to continue publishing more of my work, especially in regard to the technical aspect of it, such as the pros/cons of each tool, the methods of testing, the thinking behind the recipes, the modes of application, and more.
As for my closing words, I encourage you to stay curious.
You may never know where a very simple question could lead you in a year or two.
Dare to ask, “What if…”
Acknowledgement
The current exhibition would have not been possible without the support of many.
To Emily – I am indebted for the generosity of your time, insightful feedback, and constant support. More precisely, I am grateful for your guidance in regard to many aspects of this project, such as discussing recipes and ingredients, various application processes, methods of refinement, testing procedures, as well as making sure everything happened in a safe manner. Your presence has smoothened the journey along this somewhat rocky road.
To Jasmine – I am profoundly appreciative of the time you took to identify the various rock specimens. Without this invaluable information, the depth and scope of this project would not have been the same.
To Jess & Saivani – I am grateful for your enthusiasm throughout this project. Your curiosity and creativeness have fueled mine.
To my parents – Thank you for allowing me to monopolize the garage with buckets, shelves, crushing tools, and more (sorry !).
Furthermore, I would like to extend my gratitude to a few artists that significantly inspired and guided the direction of this project.
– Georgia Stevenson (@georgiastevensonceramis / @breakingground_)
– Nina Salsotto Cassina (@urnugent.argilla)
– Claire Ellis (@claireellisceramics)
– Sarah Howard (@sara__howard)
– Giulia Forgione (@giuliaforgione.ceramics)
– Mitch Iburg & Zoe Powell (@studio.alluvium)
– Maria Loram (@loram.ceramics)
– Matthew Blakely (@mattblakelypottery)
– Hamish Jackson (@hamish.jackson.pottery)
– Janeen Page (@janeen.page.pottery)
– Shikha Joshi (@potterybyshikha)
– Anna Maria Sand Jensen (@annamaria.sandjensen)
– Natacha Delannoy Kliber (@ndk.ceramiques)
– Don Ricardo (@don_ricardo_ceramics)