116. A Total Beginner's Guide to Making an Ash Glaze in Pottery

0:00Welcome to the Oxford Clay Pottery Podcast. I'm Catherine Tomlinson and I started an eco-conscious pottery company called Oxford Clay. Now, Oxford Clay, I don't just make pottery, I also make books and courses for other potters who want to be more environmentally friendly in their pottery making and that's what this podcast is all about and I can't wait to get started. Let's go! In this episode we're going to be talking about making pottery glazes and when you're working with any powders in pottery, powdered rocks, powdered clays, ashes, you must always use an FFP3 face mask to protect your lungs.

1:00Hello, welcome back to the Oxford Clay Pottery Podcast. I'm your host, Catherine Tomlinson and in today's episode we're going to be talking about how to make an ash glaze. If you're a total beginner, if you've never made an ash glaze, even if you've never made any glazes at all, this episode is for you and we're telling you exactly how to make an ash glaze from the beginning to the end, you can do it. If you can make any kind of, you know, recipe at all, if you've ever cooked anything, brought any ingredients together in some kind of semblance or recipe, you can make a glaze because it's exactly the same principle. Okay, so before we start the episode properly in terms of how to make an ash glaze, it's really important to say that when you're making any glazes, so probably done this already, this at the beginning of the episode, there's a little clip which is like, if you're making glazes, you must use an FFP3 face mask, but it is good to, let's just say it again, you really need an FFP3 face mask because

2:05the fine particles involved in making glazes, so for example, rocks, powdered rocks, powdered clays, ash, you really don't want them going in your lungs because they can cause a condition called silicosis and so you really need to protect your lungs with an FFP3 face mask. So this, for example, filters out the one I've got basically is kind of like loads of paper kind of folds and it filters out all the fine particles so that I'm not breathing them in and you need to make sure it's got a nice tight fit round your nose and mouth to protect you properly and so you're not breathing in any of the powders. So you need this at any stage of the glaze making process that's involving the powders. So for example, if you're sivving anything that's the powder, if you're mixing powder together that can often create a sort of cloud of dust. But once you've made the glaze and it's a wet glaze, you don't have to wear this anymore because the powders have already incorporated into your glaze. So it's really just when you're working with the powder aspects. Okay, so we said

3:08the safety warning about the FFP3 face mask, you really, really must use it. So okay, you're making ash glaze. Where do you start? Okay, so the first thing to say about ash glazes is that they do really need to be fired up to stoneware temperatures so that you sometimes hear, sometimes hear this referred to as a high fired glaze as well. And this is a reason for this is because ash glazes, they need those high temperatures of the kill and high fired glazes. So it's like 1,260 degrees Celsius. Some of them are even fired up to 1,300 degrees Celsius. You need those high temperatures in order to melt the ash particles into a glaze. So you can't really make an earthenware ash fire glaze. Some recipes I've seen have this, but there'll be like maybe a specific type of ash used if you're using say like hardwood ash, you need, yeah, from trees or something, you do need generally

4:12all the ashes that I've kind of been experimenting with. They all do need to be fired up to stoneware temperatures. So that's a first thing to say, you would need access to a kiln that can fire up to stoneware because not all electric kilns can fire up to stoneware temperatures. So you need to make sure that the kiln you're using does fire up to stoneware or the kiln that you know, you have access to is going to be a stoneware firing. So, okay, step one is to get some ash. So this is say you can use any type of plant ash, okay? So any plant can be made into an ash, which is that's one of the most incredible things about ash glazing is that you can use any type of ash. So if you wanted some ideas for different types of ash you can use and also like what they look like, what the glazes look like. Because different ashes will create different looking glazes, depending on like loads of different factors such as like the kind of the natural

5:13mineral and trace mineral, trace metal makeup of that ash that could be like the soil that's grown in, it could be like the growing conditions, like pollution, I've also heard can be a factor in terms of like what the glaze, you know, what the what what particles are in the ash, it can be yeah, like the different sort of type of plant so different plants naturally will have different trace metals and different mineral makeups in that ash. So if you want to have a look at like some different glazes and like, you know, different plants and what glaze they make, I've got a couple of books which I've done which I've created and you can buy them on the Oxford Clay website if you wanted a paper copy, get them on Amazon as well. So the first one, the first one actually is that I wrote is pottery glazing with plant ash and so that is both of these books just use one simple recipe. So that's 60 plant-based glazes from one simple recipe. So that is like it's got loads and loads of different plants in that in that book it's got like different leaves,

6:16woods, different loads of different species of plants and then the second book is a leaf ash glazing, a guide to sustainable pottery glazing with fallen leaves. So this is this is basically a book about making ash from leaves that are fallen naturally from plants mostly trees and then you can actually take those leaves burn them make them into an ash and then you can use that ash in a pottery glaze that just tells you exactly how to make it and also like those are different examples of different leaves, oak, magnolia, lime just to name a few, common lime not lime the citrus fruit. So you can also get ash by getting some ash from like say for example someone who's using wood in a wood burning stove, you can recycle the ash from wood burning stove into a pottery glaze, you could get ash from like a bonfire that's you know that's maybe burned some kind of bits of

7:17garden waste or something you know pruned branches, you can get ash from there. So a really good source is like if you recycle ash that would like normally be thrown away but you can also make your own ash from you know loads of different plants and stuff. So that's it to say that yeah you can get ash from anywhere but a really good thing to do is to try and get ash from like a single source. So for example say you know someone but it doesn't have to be the same plant but say for example someone is burning you know they're burning hardwood, hardwood makes a really really good pottery glaze so that's kind of like you know it could be like oh or something those woods that are like they're known as hardwoods they are you know some people burn them in a wood burning stove that's what I use are basically recycle ash that's people have used in wood burning stoves and some kind of people that give me that ash that they've used to heat their homes and hard and I know that they burn hardwood and hardwood ash makes a really beautiful pottery glaze it's sort of like kind of lovely

8:19quite often like transparent glaze sometimes you get like little sort of blue mist a kind of bluey white mist sometimes on the pottery glaze as well they make really really interesting makes really interesting glaze. So ash glazes are incredible and they always they generally always make really interesting looking glazes. I'm just interrupting this episode to tell you about a totally free guide I've made just for you on how to make a stoneware pottery glaze. So if you've never made a glaze before or if you make loads of glazes and you just want a recipe this guide is for you it tells you everything you need to know and it's available via the link in the show notes let's get on with the episode. Okay so you've got your ash got it from a bonfire you made your own from leaves or someone gave you some ash from their wood burning stove what do you do with it then okay so this is the difference between making ash glaze and another pottery glaze the

9:20difference is that you have to process the ash before you start making the glaze okay so again this is an ffp3 face mask moment because when you're stiff you the what you need to do with this ash is you need to sieve it okay so you need and you absolutely need to be protecting your lungs at this point you could also use goggles if you don't want the ash going in your eyes ash is coarse that you don't really want ash on your skin so you you do want to be taking some precautions like protect yourself from ash. So what you're going to be doing is you're going to be sieving it through ideally a 100 mesh size sieve so 100 mesh size is quite small and this does take quite a long time so what I do though basically get my 100 mesh size sieve I just got it from the internet it's a metal sieve and I take a spatula which you know use for cooking and I just brush the ash like gently brush the ash like through the sieve into a suitable container like a bowl or something and it does take a while so usually it's like put on a poll cast or music and

10:26I'm just like sieving that ash for ages and ages but it's really worth doing because if you don't sieve ash you can quite often get like little little bits of grit little bits of sort of stone which has come from the soil and stuff and it will make a kind of rough pottery glaze so 100 mesh size sieve I found is the optimum size in terms of getting those little particles out and also not taking loads of time because if you sieve it through anything finer it will probably take you and more time okay so some people wash their ash I don't wash my ash so washing ash basically just involves so like soaking that sieved ash or you could even do it before you sieve it you're rinsing it in a bucket you're pouring out the water you're rinsing it again then you're drying that ash I actually don't do that so really you know it's a long process and some people say that they they find it makes a better glaze because it sort of makes the glaze more even in terms of the color coloration of it some people say it makes a less good glaze because it can wash out

11:27some of the useful kind of like beautiful aspects of the glaze and the fluxes and stuff so I actually don't wash my ash yeah you'll see sometimes in pottery books like wash your ash and I don't and it's fine with a caveat that sometimes like marine marine if you're making ash from like marine plants they're like seaweeds or something they will need washing because they've got like salt in and they just don't make nice glazes unless they're washed but you're making any ash from like you know just the normal terrestrial plant then you don't need to I personally have found you don't need to wash it so okay so there we go we've got our sieved ash okay so this is amazing we've got our ash it's an ingredient that we can now use in our pottery glaze okay so the next thing is we need a recipe okay so we need an ash glazing recipe now there are so many ash glazing recipes out there those of them they'll use ash they'll use other ingredients like rocks maybe sometimes clays in different proportions but if you wanted a really simple ash glazing recipe

12:34that I've found is one of the best I've ever tested it's absolutely brilliant it's cornished stone 40 parts ash 40 parts so that's whatever ash we're using so the sieved ash 40 parts and then quartz powdered quartz 20 parts okay so that recipe makes a beautiful glaze and it's really really simple if you didn't have cornished stone you can substitute cornished stone for like a fell spa rock I've been doing some testing with that and I found that it works almost as well it's that it's like the crazes like slightly ever so slightly more but yeah if you didn't have cornished stone you can substitute it for fell spa so so if you if you're thinking where do I get these things from these rocks basically you can buy them from pottery suppliers so pottery suppliers will be able to sell you these as like powdered rocks again when you're working with them you must use an ffp3 face mask but they'll send them to you so maybe in a like a container or a bag

13:38and then what you're doing next is you're going to just weigh out those ingredients according to the parts in that recipe so if you wanted to make for example like a test so what I do is I basically convert it to grams so if you think about it you can think about it as parts or you think about it as like a percentage say for example we're talking about like the 40 parts ash or 40% ash so you can just calculate however much glaze you want say for example you want to make just a little glazed test of like 100 grams or something just see how it goes like then it would be 40 grams of ash 40 grams of cornished stone and then 20 grams of course so in glaze recipes the water is never specified but we're going to be adding water to those ingredients next so that's the next thing to say is that just if you want to make more glaze you're just scaling it up again you're doing percentage or parts you can add like oxides if you wanted to add coloring oxides to ash glazes

14:41they do work really really well actually because of the fluxes in the ash so yeah I've actually got a book which you can get on the ox or clay website about color eco-conscious pottery color and in that book I use different coloring oxides which I've made from recycled metals so it's like iron and copper so it's their degree which I've made from copper and just rust and I've been at experimenting with adding those to different base glaze recipes and like ash a lot of them are ash glaze recipes and they make really beautiful glazes so yeah if you wanted to add any oxides to your glaze you add those on top of the base glaze recipe so say for example you're making a little glaze test and is the recipe says like 1% ver degree you would add 1 gram of ver degree to that glaze test if you're doing a hundred grams of glaze so say for example you want to make more glaze you want to make a kilogram of glaze then you would scale that up to 400 grams of ash and

15:45four of sieved ash 400 grams of cornish stone and 200 grams of quartz so that's how glaze recipes work in terms of the parts um okay so yeah the next stage so we're going to we've weighed everything out we've put it uh they're all powders we've worn our face mask we're just using kitchen scales to weigh it out weigh the ingredients out separately in case you need to take any bit out of that bowl again you know in case you accidentally put too much in it they're really difficult to separate it's what all glaze glaze uh ingredients are basically like white powders they're quite difficult and obviously they've mixed together that you wouldn't be able to take out the the bits if you know accidentally added too much the bowl so I weigh out them separately and then I add them all together at the end in terms of like yet to a bucket so you want to suit a full glaze making vessel ideally with a lid so a bucket is a great idea a lidded bucket you can get those from again from like pottery suppliers you can use any kind of you know anything with a lid say for example the Tupperware Pop you're making a little bit of glaze you can use a jar so anything

16:48with a lid because that just stops the glaze from drying out um okay so the next thing you're doing is you're going to add water so like I just said um so just a second ago that water is never really specified in terms of like how much to add to a pottery glaze and that's because I think that um the like people who make glaze recipes they don't necessarily know how thin you want the glaze or how thick you want it or the that you're um you know it just you just might need a different amount of water than they specify if they did specify it in a recipe but um generally with ash glazes you want to make it into the consistency of sort of single cream but kind of like on the thick side because I found that ash glazes actually work better when they're a little bit thicker so um you know again you can experiment with this you can make it make your glaze and then you know test it and then see oh that was a bit of thin maybe the ash glaze needs to be a little bit thicker um you'll to be able to tell if it's too thin because it might go rough with ash glazes

17:50so quite often on the rims of my pot so I do get a little rough surface if it hasn't had enough glaze on there um that's how to tell it it's a bit thin or that that can also be a sign of underfiring actually as well but um so so if you if you haven't added enough water to your glaze you can obviously just add more but if you um have you think you might have added too much water just wait for that glaze to settle it won't take too long and then you can just scoot especially with ash glazes they settle really many quickly and then you can just scoop the water off the top and then you're back to the glaze of the consistency that you want okay so you've got your you've weighed out all the ingredients you've added the water it's in a bucket the next thing you need to do is sieve the glaze again so this might seem like really laborious like why am I um sieving this glaze again I've already sieved ash has taken me absolutely ages but it really is worth doing because it makes sure it makes sure that all the ingredients are properly dispersed in that glaze so especially ingredients like cornice stone they can often stay in like little

18:52tiny lumps and stuff if you're adding any kind of oxide to the glaze sieving it is really important because it will really disperse that oxide like throughout the glaze so um yeah sieving it again again the same thing with a hundred mesh size sieve it'll probably be more it probably be too difficult to sieve an ash glaze with a with a smaller mesh size sieve than a hundred that's probably the lowest the minimum you can go in terms of like whole size and again just use your spatula you're just sieving it you're just pushing the glaze through you can you know you can pour it in with a jug or something pushing it through into your container again just making sure you won't need to sieve it once just through the sieve all the all the way all the way through sieve it once and um and your glaze is ready to use so the thing with ash glaze is like I said they do settle really quickly so before you use it just make sure you um give it a little star every time you're dipping a pot in it's a really good idea just to give it a stir to kind of make sure it's all mixed and then dip your pot in and next the pot just give it a little stir

19:53again and and then dip it again because they do settle really really quickly but um yeah so before you use your ash glaze stir it really really well um to make sure all the ingredients are kind of incorporated they quite often get like a big sort of sludge at the bottom so just make sure yeah just make sure you sit you're stirring it every you know each time you're using it um and then a really good idea is labeling your bucket that you've got the glaze in again like you know I said about the lidded make sure it's lidded because it just it will just stop your glaze from drying out it have to have a lid but it's a much easier thing to do than like to be adding water to your glaze every single time mixing all up again so um yeah really good idea to keep it in a lidded container yeah and then labeling it with like whatever made whatever glaze you've made so you've made a a beautiful glaze from like Ivy leaves which does make it amazing for them Ivy leaves does make an amazing glaze yeah just label it and um and there you go you've made your glaze so yeah so make sure you're using your FFP3 face mask um throughout the time we're using the

20:56powders and then a really good thing to say about important thing to say about ash glazing when their wet glazes is that you don't need your FFP3 face mask anymore because all the powders have been incorporated into the glaze but ash glazes like I said at the beginning are caustic so you don't really want to be getting it on your hands so if you normally dip your pot in with your hands you could try glazing tongs instead or you could wear gloves and to to dip your pot in or you could try pouring the glaze over the top of your pot but you don't really want sustained contact with ash and your hands because it can like yeah it can hurt your skin um yeah and you could use safety goggles if you wanted like an adipra caution against like splashes going in your eye or something um that would probably be a good idea as well so um that's how to make an ash glaze and like uh the other thing it needs to be fired the same way temperatures but that's it so the only difference to making ash glaze to making like you know any other any other pottery glaze um is that you just need to process the ash first so you need to source you know get a source of ash

22:00and then you just need to sieve it and then it's ready to go in terms of your ingredient um and another important thing to say actually is that quite often when you're looking for an ash glaze recipe if you're a bit you know thinking where do I get um you know ash glaze recipes from there's those are books on ash glazing um you can use a recipe in this episode i'll put it in the show notes as well that's a really good recipe um you can get loads of different recipes you know from different sort of pottery books they'll probably say um to say they'll probably say wood ash in the glaze recipe but you can just substitute the word wood for ash well any any kind of plant ash so you know if you wanted to make like to try out some uh an ash glaze made from leaves if a recipe says wood ash you can just use leaf ash that's absolutely fine so um don't think you have to use wood ash if it says wood ash lots of older glaze recipes specify wood ash that's just because that's what people were kind of generally using then but you can use yeah you can use leaf ash you

23:02can use you know offcuts prunings you have to use like wood ash yeah um yeah so if you wanted um yeah the recipe like i said uh all there's um yeah the same recipe is in the books on ash glazing available on the also clay website another really good source of of recipes uh glit ash glazed recipes is a website called glazy.org so that's when potters will just like have their recipe upload it and then you can see what it looks like that's actually where i found that uh my my tried and tested ash glazed recipe which i use with like all my pottery the one i said in this episode it's such a good recipe i actually found that on glazy.org um and yeah it's so nice potters just sharing recipes and then like you can see what they look like and stuff they often have photos of the of what it looks like which is um it's really nice it's really good good good website free to use you can search by um key words or search for ash and found that recipe um yeah oh well thank you so so much for joining me if you wanted to make an ash glazed you absolutely can it you

24:04definitely definitely can do it um it's uh yeah it's it's a really fun area of pottery it the world is your oyster in terms of like the creativity that you can make from ash glazes and all the different incredible glazes that you can make with like one recipe just by switching the type of ash you use you know by sort of testing different uh you know eco-friendly oxides um made from recycled metal oh so much so many amazing um glazes that you can make from ash from ash glazing so it's a really amazing area of pottery and thank you so so much for joining me on this episode me talking about ash glazing again which i love um and yeah wishing you very very happy potting until the next episode and i will see you soon goodbye thank you so much for joining me on that episode and if you want to find out more about eco-friendly pottery head over to the ock the clay website which is www.oxvidclay.co.uk i can't wait to see you there

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