MOUNTAIN pottery // Ash Glaze testing

This is the long-awaited post on my test result for the ash glazes I was researching. And because you have waited so long the pressure is on to not disappoint. I think the outcome of some glazes are defiantly worth the wait  though.


Click thumbnail to view gallery, click again for larger version.

note *** if you can’t be bothered reading about my troubles skip the next 3 paragraphs : )

So after promising that I wouldn’t make you wait so long between posts, that all went to hell with the last few mouths that we are having. Actually this whole year has been one thing after another, but this time I’m not going to say I think it’s all settling down now, because just after I said that the last time we ended up unexpectedly moving house!

So that’s what has been getting in the way of making stuff this time, it seems like there is always something…we didn’t intend on moving any time soon, but an offer came up the was impossible to refuse, and although we loved our mountain home our new place is equally as beautiful and we finally get sun which we have longed for since we first moved to the shady gully 5 years ago, I can even have a vegetable patch now, it makes me happy. But moving house… I hate moving house, I think it has to be one of the most stressful things, traumatic really : )

So that’s done, and in between that my very cute bunny  Arnold, that I just got for my birthday in June had a horrible accident and now he can’t hop anymore, which was extremely upsetting, he still get around but he has nerve damage which interrupts his movement signals. I was caring for him night and day, he had to be spoon feed and watered every few hours while he was recovering, and changing his bedding and keeping him clean was a big job. But I am happy to say he has improved and is managing, he’s not in pain, and it’s not ideal but he really does seem happy, and is still as playful as ever, he is sooo cute. So add to the list of things to do, make a bunny wheel chair. I will keep you updated on his cuteness in the mean time.

Anyway he has been taking up a lot of my time and is just now becoming more independent again, so I can get back to work, start making things and stop having to explain why I haven’t been doing so. But incase I don’t post for several months again, just assume that what ever else is left that could happen, has happened, and that once I have sorted it out you will be the first to know.

Now speaking of back to work, here it is the work I was doing at the very beginning, my Ash Glaze assignment. Everyone in our glaze class had to choose a glaze type to research and present to the rest of the class, ie- Jun, Shino, oil spot, celadon, matte, transparent, blacks, whites, iron reds, etc. I chose ash glazes because I like their simplicity, I just love the idea you can mix two ingredients that you get for free, clay out of the ground, and ash out of your fireplace and have a glaze, its amazing. I also like that it was the beginning of all glazes and think its a good place to start, as well as its link to wood firing which I love.

So I got to work researching and founds it’s a never-ending topic (like all ceramics) and although it is such a simple glaze is also so complicated with all its variation, different wood types to make different ash, or even types of hay or rice hull which I did test, different processing for different results, to wash or not wash ash, how to build firebox to burn wood to make ash, it just doesn’t end. And in the end I was left thinking that copper reds would have been a breeze compared to this, haha, but I loved it anyway.

Interesting things that I came across when research that I thought were worth a mention was the way Phil Rodgers (the ash glaze expert) creates forms for the ash glazes he uses. He talks about making a cup or vase with indentations, score marks or rings to catch fluid ash glazes, and showcase their nature. The characteristics of an ash glaze are just that, fluid and sometimes just runny, and often need a foot ring to catch the glaze so it doesn’t end up on your kiln shelf. I like the idea of really considering a glaze and how it likes to work, and making a form that works together with the glaze, not separate from it.

Another important factor of ash glazes is obviously the ash you use. Basically hardwoods make for more stable, stiffer glazes that are more opaque or even matte in appearance, where as soft woods give more transparent or translucent fluid appearance, with more of a gloss. This is not alway the case but is important to note when choosing wood to make ash.

Also different woods take up different minerals from the earth when they are living as food and nutrients, this inorganic material is what is left over in ash after the organic material is burnt off. These minerals are what makes up the flux and glass former in a glaze recipe, and with the addition of a stabilizer or stiffener alumina, in the form of clay or kaolin you have the three components for a glaze, without having to mine to get them. I find that exciting.

So the wood you choose greatly affects the results you achieve, because some wood may carry more calcium or potassium (a flux) than others or in the case of rice hull ash, and extremely high amount of silica (a glass-former), around 95-98%, which stays unmelted in the glassy matrix of a glaze because it is an excess of silica, therefore it becomes a white opacifier (instead of melted glass). This type of glaze is known as nuka in Japan. I experimented with this a little, by burning rice hulls, (the hard way in a portable barbecue, which I don’t recommend because it took hours of constant blowing on to keep alight, and lungs full of smoke. And then I realized there is a much easier way, to just put it in a saggar in a gas kiln and bisque fire it, or “calcined” it, next time..). This is shown in the images in the gallery the fire in the bucket.

I also experimented with washing ash over 5 days, this is thought to make the glaze mixture more stable by washing out the soluble alkalis in the ash (in unwashed ash these contribute to the fluxing of the glaze). So by washing them out the glaze is supposed to be less runny and keep longer in wet form – ash glazes only keep for a few weeks once they have been mixed up with water, after that, all the soluble material in the ash stays separate from the glaze mix in the water. When you go to glaze a pot, the water soaks into the pot, taking with it the fluxing ingredients into the body of the pot, and leaving the rest of the ingredients on the outside of the pot. When you come to fire the pot, because most of the fluxes are in the body of the pot, not the surface, they don’t take part in the melt, which leave you with a glassy pot underneath a flaky outer shell on the surface. In the end I didn’t even end up using the washed ash because it was a hassle, but I want to do some more testing on my own with this.

Everyone in the class got two of the glaze recipes I collected to mix up, then I numbered and dipped all the glazes mixed and fired both in reduction and oxidation. And here are the results, they were really pleasing, all interesting and some just really beautiful. The rice hull ash glazes where nothing special but I believe this to be due to the ash not being processed properly and I will need to do further tests and get back to you with those ones, I really want to re-test the Shoji Hamada rice hull glaze recipes.

My favorites are-

# 6 – stony matt (different every firing, pale green glassy transparent, to pale green opaque lovely in wood firing)

# 7 – ochre ash (satin/matte opaque yellow with rusty iron spots on thicker application, oxidation or reduction)

#10 – wood ash (satin/matte black in oxidation)

#19 – teadust (satin dark metallic grey, with variations of ochre and maroon with thin application, oxidation or reduction)

#25 – simulated nuka (thickly applied, opaque white with edges slightly breaking black, rustic, textured and pinholy)


all glazes shown here are contaminated with cobalt that was somehow in the wood ash, so although ash glaze results always vary hugely anyway by nature, these ones, even more so. And if you notice a test being blue without the recipe having cobalt in it, it is because of this contamination.

If you are interested in ash glazes to I defiantly recommend getting Phil Rogers book  – Ash Glazes , and if you have any questions about my test, post a comment and I would be happy to help.

Feel free to print these recipes off and test some yourself, I would love to see your results if you do.


About MOUNTAINpottery

Mountain Pottery is designed and handmade by Deanne Sarita Smart. The studio is located in a small town of Sassafras in the Mountains of Australia. This pottery is made to be collected, loved and used everyday as some of your most treasured belongings. Each piece is unique and made to order. Aside from being beautiful and functional objects, each collection has an underlying meaning, message or intention. All the vessels are inspired in some way by myth, nature, and symbolic language. About this blog // This blog is designed to be a place of inspiration to others with the same interests and point of view, as well as a look into the creation of Mountain Pottery.


  1. The pictures looks great. And I agree – I hate moving house and I’ve been doing it every year for the past 3 years. I dread it. But what can one do?

  2. Thanks, and I really feel for you, no one should have to move that many times : ) I hope they were at least by choice!

  3. Great project! Fantastic pictures of the process…

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