Saggar Fired Pottery

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:

a saggar loaded with pottery
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 in the saggar
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.
pots in a saggar with everything burnt away
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 firing
pottery stacked to show how few pieces fit in a saggar.
The sagger is a really inefficient way of firing pottery, you can’t really fit much in.

Finished Work

tiles with shell marks left on them
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 reduction
pottery jar made to look like a rock
I 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.
saggar fired wonky pot showing oranges, reds and whites
a wonky pot fired in the saggar brings out so many different surfaces and colours
a little wonky pot on a cyclinder
Recently 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 bases
budvase on a plinth
I 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.
side profile of a budvase
You can see the striations that the mare’s tail left in the glaze, they just help give antooher texture to the potttery.

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  1. 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.

    1. 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.


      1. 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!

        1. 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.

  2. 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?

    1. 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.


  3. 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?

    1. 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.

  4. 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

    1. 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.


  5. 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?

    1. 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.

  6. Hi Joseph, how thick do you make the saggar, I fancy having a go at this. Thanks Alan

    1. 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.

    1. 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.

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