13 Amazing Reasons to Make a Pottery Glaze from Fallen Leaf Ashes.
Experimenting with different plant leaf ashes in glazes is so much fun! Each plant’s fallen leaves have a unique mixture of minerals and trace metals and therefore create a different-looking pottery glaze.
Even plants that are the same species but growing in different soils, or under different climatic conditions can have a unique mineral and trace metal combination in their leaf ashes.
The more I experiment with ash glazing, the more I realise the amazing potential of using fallen leaves, shed naturally by plants, in pottery glazes.
I’ve put all my experiments glazing with fallen leaf ash in this book: Leaf Ash Glazing: A Guide to Sustainable Pottery Glazing with Fallen Leaves
This blog post is an extract from the book Leaf Ash Glazing: A Guide to Sustainable Pottery Glazing with Fallen Leaves
13 Amazing Reasons to Make Leaf Ash Pottery Glazes
Reason #1: Leaf ash glazing connects you to an ancient pottery practice
Ash glazing has been practised for thousands of years. Making your own ash glaze connects you to this ancient pottery tradition.
Reason #2: Leaf ash glazes have simple recipes
Ash is such a complex ingredient containing so many different minerals, so glaze recipes using ash are often very simple.
The simplest one is just ash and clay! The recipe in this book uses just three ingredients, leaf ash, Quartz and Cornish stone, switching the leaf ash used each time to create a new glaze.
Reason #3: Leaf ash glazing creates many different unique glazes
Each plant ash has a totally individual mineral and trace metal composition, so each leaf ash glaze will be entirely special and unique.
Reason #4: Ash glazes work well with recycled colourants such as homemade metal oxides.
All plant ash glazes are high in naturally occurring fluxes. Fluxes are substances in a glaze that make it melt when heated, and help to bring out the colours in any colouring oxides added to the glaze.
When colouring oxides are painted on top of a leaf ash glaze they produce bright and beautiful colours. Leaf ash glazes work particularly well with homemade colouring oxides created from recycled metals such as copper (verdigris) and iron (rust).
Learn more about creating Eco-conscious pottery colour in the book, Eco-conscious Pottery Colour
A guide to colouring ceramics with scrap metals, glass, plant ash and clay
Commercial metal oxides normally used to colour pottery are among the least environmentally friendly pottery materials. But what if it was possible to colour ceramics without using these? This book will show you how!
Learn four innovative eco-conscious ways of creating colour in ceramics by:
Recycling scrap copper wire into verdigris, and rusty iron into iron oxide.
Repurposing the colouring oxides in scrap glass.
Making pottery glazes from plant ashes containing naturally occurring metal oxides.
Using metal-rich clays to colour glazes.
Includes 80 stoneware pottery glaze recipes made with eco-conscious colourants (fire to 1260 °C / cones 7- 9).
Perfect for those new to pottery and experienced Potters who want to learn how to colour their ceramics more eco-consciously.
The book is in PDF format and is delivered via a digital download.
Reason #5: Leaves are a free and abundant glaze-making ingredient
Leaves are free and abundantly available. Leaf ashes are a glaze-making ingredient unaffected by global supply chain problems and price fluctuations.
Reason #6: Leaf ash can be locally sourced
Leaf ashes can be sourced locally, reducing the environmental impact and CO2 emissions associated with the international transportation of other pottery materials.
Other ingredients used in ash glazing can also be sourced as locally and ethically as possible. Sourcing pottery materials from areas with high levels of regulation and robust civic structures will ensure that they cause minimal impact on humans, animals and the environment, during mining and processing.
Pottery suppliers usually have access to information about where their materials are mined.
Reason #7: Plant leaf ash is a renewable pottery material
Most pottery materials such as ball clays, china clays, metal oxides (processed from metal ores), and rocks have been created over millions of years by natural geological processes.
Like fossil fuels, metal ores, clays and rocks are considered non-renewable materials because of the length of time they take to form. Non-renewable pottery materials are depleting over time due to mining. China clay stocks in St Austell, Cornwall in the UK for example, will last for around another 50 years.
Declining ore grades mean that mining companies must often mine deeper using more energy to create pottery materials such as metal oxides.
Plant ash is one of the few pottery materials that is renewable because it can be continuously created from growing plants. This is especially true of plant leaves that are grown and shed by plants as part of their natural growing cycle. By using plant ash glazes, particularly those made from fallen leaves, Potters can reduce their dependence on non-renewable pottery materials that are extracted from the Earth.
Reason #8: Using ash in glazes reduces mining
The mining of non-renewable pottery materials can cause damage to humans, animals and the environment. Extracting materials from the Earth can cause deforestation, loss of habitat, heavy metal pollution and water contamination. Particulate matter from mining can also cause air pollution, damaging the environment and human health.
The destructive effects of mining on ecosystems cannot be easily reversed. By using plant leaf ashes in pottery glazes Potters can reduce their use of mined pottery materials.
Reason #9: Leaves create more ash than wood does
Leaves create more usable ash than burning wood. Wood creates around 0.5% of usable ash per dry weight of wood, whereas naturally fallen plant leaves create around 5% to 15%. See the table on pages 60 - 64 for the usable quantities of ash produced by 36 different types of leaf.
This means that fewer leaves need to be collected from the environment than wood to make the same quantity of pottery glaze. Unlike wood, leaves are naturally shed by plants and continually renewed.
Reason #10: Plant leaf ash prevents erosion caused by deforestation
Mining pottery materials often involves clearing land of vegetation, reducing habitats for plants and animals, and causing loss of biodiversity.
Removing plants to make way for mining causes increased soil erosion and increased risk of flooding due to the lack of plant roots holding the soil together.
Creating pottery glazes from naturally fallen plant leaves does not damage plants, ensuring that their root system remains undisturbed in the soil, retaining habitats for wildlife and preventing soil erosion.
Reason #11: Leaf ash glazes are a more environmentally sustainable and ethical way to colour pottery
Many concerns have been raised about the harm caused by mining commercial metal oxides to people animals and the environment.
Commercial metal oxides are destructive to the environment and very energy-intensive to mine from the Earth. Mining for metal oxides can also pollute the environment. The Southern Katanga region of the Democratic Republic of Congo for example has been named as one of the top ten most polluted areas of the world due to Cobalt and Copper mining.
Many metal oxides also have significant informal or ‘artisanal’ mining operations alongside commercial ones. Artisanal miners work with hand tools to mine and sort the ore by hand. Artisanal mining is an unregulated industry and miners work in extremely dangerous conditions without safety equipment or legal protections.
As a result, many artisanal miners are at risk of health problems such as respiratory and skin disorders, and injuries or even death from mining accidents.
The Democratic Republic of Congo currently produces more than 80% of the world’s Cobalt, which creates the colour blue in pottery. Up to 30% of this Cobalt is mined by artisanal miners. Metal ores are mixed after mining, before being transported internationally for processing, so it can be impossible to know whether a metal oxide has been artisanally mined or not.
Amnesty International has found that thousands of children, some as young as 6 years old work in the Cobalt artisanal mining industry. Some experts believe that there could be around 35,000 children working in the Cobalt mining industry alone. Artisanal mining has also been shown to exacerbate inequalities in societies. Whilst the work of women is relied upon to heavily to support artisanal mining activities, the benefits they receive for this work are small by comparison.
Plant ashes contain naturally occurring metal oxides which can add subtle colour to a pottery glaze without the use of commercial colouring oxides.
Reason #12: Being in nature is good for you
People have lived in forests since ancient times and there is so much evidence that spending time in nature has a positive effect on physical and mental health. In Japan, shinrin-yoko or forest bathing is often prescribed by doctors for patients suffering from depression, stress and overwhelm. The physical benefits of spending time in nature include lower blood pressure and a boosted immune system. In fact, it is thought that a substance emitted by plants and trees called phytoncides naturally boosts human immune systems and that these effects last for several days.
Reason #13: Foraging is a natural activity for humans
If the whole of human history was condensed into a day, we only stopped foraging around an hour and 20 minutes ago! Humans have been foraging for thousands of years. Our bodies evolved to roam the land to gather and harvest wild foods. Gathering leaves for glaze-making brings us back to our natural state.
Learn how to make your own pottery glaze from fallen leaves.
In the book Leaf Ash Glazing: A Guide to Sustainable Pottery Glazing with Fallen Leaves, I take you through the simple step-by-step process to make your own beautiful stoneware pottery glazes from leaf ash. From identifying and collecting leaves and processing them into ash, to creating unique high-fire leaf ash glazes – it's achievable even if you've never made a pottery glaze before!
Get a full guide to glazing with fallen leaves in this ebook
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Tomlinson, K. (2022) Pottery Glazing With Plant Ash: 60 Plant-Based Glazes from One Simple Recipe. Oxford: Oxford Clay Publishing.
