For the last year I have been experimenting with firing inside a saggar inside my electric kiln. From the start I have to say anything fired in this method I wouldn’t sell as food safe and to make certain of that I don’t make functional ware with this method, just things that are purely sculptural, albeit quite small sculptures.
So what’s a saggar and what does it do?
A saggar is a sacrificial pot that was originally used in industry to keep ceramic glaze free from ash during the firings, especially with coal as this can make the wares quite dirty. Unlike industry I use my saggars in reverse, I fill them with combustible materials and the pottery so then I can get different affects as the ash combines with the glaze or the ceramic body itself.
This makes a reduction inside the saggar chamber itself which strips oxygen from the clay body which makes the clay itself change colour. This sort of atmosphere is damaging to the electric elements in an electric kiln and the saggar protects the kiln from damage
Pictures of the process:
The kiln is loaded with shells in between the layers so then the pottery doesn’t stick to each other in the firing.Seaweed and mare’s tail are local to where I live and are very high in silica which means they leave deposits of their own form on the pieces, I don’t tend to just bung it all on top it is more carefully places.The mares tail is so high in silica some of it remains throughout the firing, but it easily washes away when I clean up the pottery after the firingThe sagger is a really inefficient way of firing pottery, you can’t really fit much in.
Finished Work
the shells leave a ghosting affect both from their own decomposition and because they leave small oxidised areas where the pottery is protected from the ash and reductionI cut my thumb in MAy and couldn’t throw for weeks so made some of these lidded rocks out of solid lumps of clay, these all turned out so different to the thrown work.a wonky pot fired in the saggar brings out so many different surfaces and coloursRecently I made some mini wonky pots and pout them on plinths that comes from the bins at my day job, so I trimmed them into circles and stuck them together before sanding and polishing them, they make interesting little basesI like using some different clays sometimes for example this clay is ES5 which is low in iron so doesn’t take on an much iron flashing in the saggar.You can see the striations that the mare’s tail left in the glaze, they just help give antooher texture to the potttery.
Or how something I created due to injury became of of my favourite ceramic creations. In 2018 I was preparing for Earth and Fire in Nottinghamshire and working as a Design Technology Technician (wood, metal and plastics) as a day job, I was using a bandsaw which was something I did most days as I was generally using the laser cutter and supervising classes at the same time. Our bandsaw wasn’t the best, it was in all likelihood bought by the school long before I was born and it was in constant need of TLC. Regardless, as I made a…
The Harris Museum commissioned a film about my making process, which is interesting to watch. As a maker I am infinitely influenced by the sea, whether it is painting patterns, carving boats or actually using found materials as part of my making.
For the uninitiated, I should explain what a Saggar is, it is a big piece of pottery that smaller pottery is sealed in. Traditionally this was done in Stoke on Trent to protect the pottery from the coal fire that they fired their kilns with. Modern Potters use them to get a reduction environment inside an electric kiln, this stops the kiln from getting damaged and brings some different effects to the pots. I threw a a saggar a few years ago and it has been sat on the top shelf on my studio for a few years now, not…
So this week I made some prototype saggar formers and saggars, I mixed my own clay with sawdust, grog from broken pots and some molochite for added strength. Now if I didn’t have a deadline I would let them dry over two weeks, but I had a deadline so I force dried overnight and fired the next day so you will see some cracks in the larger saggar. Also if you want to make a saggar former don’t leave such big gaps as the clay can get stuck in them making the harder to remove.
For a while I have been thinking about tiles as an act of experimentation, they are something that can be created in the fraction of time for throwing, there is a lot less focus that goes into creating them, no hunching over the wheel. In some ways they are quite disposable. I don’t generally use tile for glaze tests as they don’t have gravity and thickness’s similar to pots but I do use them to test ideas, patterns, new and more recently my saggars to see what effects are possible. In these sorts of ways the tiles are part of…
16 Comments
Very interesting!
Please, what do you make the saggars out of, is it fireclay or something else?
And does the lid of the saggar fit tightly or do you find it better to leave it a bit ‘gappy’?
I love your pots, inspiring me to try!
Thank you.
Peter
Due to limited space for different bagged clays I make them out of my standard clay body which is relatively inexpensive stoneware clay from Spencroft, usually I’ll add some grog not that I have noticed it help with the lifespan of the clay.
I have thrown them and I have made them using slabs.
The lid is sealed on tight with wadding which is a mixture of china clay and alumina, which can also be used to help pots not stick to each other. No flour in the wadding as this burns out and and causes reduction in the kiln chamber.
Because I have a small kiln I will make and bisque fire for a few weeks and then saggar fire until the saggar literally falls apart so won’t move it out of the kiln until its cleared.
Hi Joseph,
Thanks for sharing your process; very interesting & helpful and I love your results! Getting ready to fire my first test saggar, I wondered what the alumina-kaolin ratio is for your wadding to seal the saggar?
Thanks so much!
Roos
Hello. This is fascinating, thanks so much for sharing. I was just wondering whether you use a terra sigillata or any other glazes or are the effects purely caused from the organic materials and reduction atmosphere?
I haven’t used terra sigillata yet, I have plans to in the future. There is glaze on some of the pieces, and slips too but a lot of the effects are caused by the organic materials and the reduction in the Saggar. the organic materials even interact with the glaze very differently.
If there is glaze on a piece it is merely Leach 1234 either with iron added or just plain as is. I do make some of my own clays to play to the effects too. I do have some pieces that are traditionally wood fired with the same combinations of glazes slips and clays ad they are very different to what comes out of this sort of firing.
I have heard mixed news around whether firing saggars/ any reduction materials in an electric kiln shortens the life of the elements. Have you found this to be the case?
I haven’t noticed an damage to the elements themselves or to the bricks.
The only time I had reduction in the actual kiln chamber was when I added flour to my wadding mix and them used it to seal the saggar. Otherwise the reduction doesn’t penetrate the saggar. I have a fragment of one of the saggars where you can see heavy reduction inside, where the iron in the clay has darkened significantly but the outside shows no reduction at all, with the clay being still buff in colour.
Great blog – thanks for sharing. How hot are you taking these firings? Have you ever put a cone in the sagger pot to see if the pot doesn’t get as hot as the rest of the kiln?
I only have cones five, six and seven. At 1200 C both inside and outside the saggar cone 7 is flat because it takes so long to reach 1200C in my plug in kiln that the heat work is pretty even.
Hi Joseph,
Thank you so much for sharing your process – very generous of you! I am definitely going to try this. I have a couple of questions…..
Do you use sawdust in your saggar at all?
You mention you mix china clay and alumina to make the wadding. Do you mix them in powder form and then add water to make a putty like consistency?
Thanks,
Cathy
Yes I use saw dust, I know people who use charcoal too.
Yes I just mix the wadding up to a putty. For inside the saggar you can have flour in the mix but for sealing the saggar don’t because it burns out in the firing. I have used wadding from the inside of the saggar a few times so it doesn’t go to waste.
Hi Joseph,
Hope you’re well. So I made a really big saggar (thrown on the wheel), using your sealing-the-lid-method (still very grateful!), and actually managed to turn an entire red earthenware coffeepot + accessories pitch black (apparently red Fe2O3 transforms to black FeO in reduction). You can see a picture here, if you’re interested: https://www.instagram.com/p/CsTmxJ-oOXt/?utm_source=ig_web_copy_link&igshid=MzRlODBiNWFlZA==
Very cool. Yes exactly black FeO is why stoneware clay gets a speckle when reduced. If you vary how much you are burning in the saggar you can vary how much reduction you do.
Very interesting!
Please, what do you make the saggars out of, is it fireclay or something else?
And does the lid of the saggar fit tightly or do you find it better to leave it a bit ‘gappy’?
I love your pots, inspiring me to try!
Thank you.
Peter
Hi Peter,
Due to limited space for different bagged clays I make them out of my standard clay body which is relatively inexpensive stoneware clay from Spencroft, usually I’ll add some grog not that I have noticed it help with the lifespan of the clay.
I have thrown them and I have made them using slabs.
The lid is sealed on tight with wadding which is a mixture of china clay and alumina, which can also be used to help pots not stick to each other. No flour in the wadding as this burns out and and causes reduction in the kiln chamber.
Because I have a small kiln I will make and bisque fire for a few weeks and then saggar fire until the saggar literally falls apart so won’t move it out of the kiln until its cleared.
Hope this helps.
Joseph
Hi Joseph,
Thanks for sharing your process; very interesting & helpful and I love your results! Getting ready to fire my first test saggar, I wondered what the alumina-kaolin ratio is for your wadding to seal the saggar?
Thanks so much!
Roos
Generally I do a 50/50 mix, but could probably get away with clay 60:40 alumina because that would be cheaper and slightly easier to deal with.
Hello. This is fascinating, thanks so much for sharing. I was just wondering whether you use a terra sigillata or any other glazes or are the effects purely caused from the organic materials and reduction atmosphere?
I haven’t used terra sigillata yet, I have plans to in the future. There is glaze on some of the pieces, and slips too but a lot of the effects are caused by the organic materials and the reduction in the Saggar. the organic materials even interact with the glaze very differently.
If there is glaze on a piece it is merely Leach 1234 either with iron added or just plain as is. I do make some of my own clays to play to the effects too. I do have some pieces that are traditionally wood fired with the same combinations of glazes slips and clays ad they are very different to what comes out of this sort of firing.
Joseph
I have heard mixed news around whether firing saggars/ any reduction materials in an electric kiln shortens the life of the elements. Have you found this to be the case?
I haven’t noticed an damage to the elements themselves or to the bricks.
The only time I had reduction in the actual kiln chamber was when I added flour to my wadding mix and them used it to seal the saggar. Otherwise the reduction doesn’t penetrate the saggar. I have a fragment of one of the saggars where you can see heavy reduction inside, where the iron in the clay has darkened significantly but the outside shows no reduction at all, with the clay being still buff in colour.
Great blog – thanks for sharing. How hot are you taking these firings? Have you ever put a cone in the sagger pot to see if the pot doesn’t get as hot as the rest of the kiln?
Thanks – Jesse
Hi Jesse,
I only have cones five, six and seven. At 1200 C both inside and outside the saggar cone 7 is flat because it takes so long to reach 1200C in my plug in kiln that the heat work is pretty even.
~Joseph
Hi Joseph,
Thank you so much for sharing your process – very generous of you! I am definitely going to try this. I have a couple of questions…..
Do you use sawdust in your saggar at all?
You mention you mix china clay and alumina to make the wadding. Do you mix them in powder form and then add water to make a putty like consistency?
Thanks,
Cathy
Yes I use saw dust, I know people who use charcoal too.
Yes I just mix the wadding up to a putty. For inside the saggar you can have flour in the mix but for sealing the saggar don’t because it burns out in the firing. I have used wadding from the inside of the saggar a few times so it doesn’t go to waste.
Hi Joseph, how thick do you make the saggar, I fancy having a go at this. Thanks Alan
About 10mm thick with my saggars but the exact thickness isn’t that important. One warning they will eventually break apart from the repeated firings.
Hi Joseph,
Hope you’re well. So I made a really big saggar (thrown on the wheel), using your sealing-the-lid-method (still very grateful!), and actually managed to turn an entire red earthenware coffeepot + accessories pitch black (apparently red Fe2O3 transforms to black FeO in reduction). You can see a picture here, if you’re interested: https://www.instagram.com/p/CsTmxJ-oOXt/?utm_source=ig_web_copy_link&igshid=MzRlODBiNWFlZA==
Very cool. Yes exactly black FeO is why stoneware clay gets a speckle when reduced. If you vary how much you are burning in the saggar you can vary how much reduction you do.