5. The Oven Entrance and Chimney

The oven layer is complete!

Just a dome-shaped sculpture without the entrance and chimney.

You have completed your first layer and now you need to build a nice entrance at the front of it in order to get food in an out (unless you leave it as a dome shaped sculpture!). At this stage we will also be removing the sand former and building a chimney.

You should have left the oven layer to dry for at least 4 hours before you attempt to cut the oven door but don’t leave it so long that the clay-sand mixture dries too hard or you will find it tricky to cut.

The dimensions of the entrance are dependant on the dimensions of your oven. Generally though, you don’t want it so big that it effects the heat retaining potential of your oven nor too small so you can’t get anything bigger than a tiny pizza through it.  In the end I chose the width of my door based upon the width of a standard roasting tray and, as it happens, the width of the bakers peel I had bought.  Don’t worry too much about the height at the moment because you will probably adjust that later on once you have fired it.

The oven entrance removed revealing the internal sand former

The oven entrance removed revealing the internal sand former

Roughly mark the width and curve of your oven entrance and then, using nothing other than a carving knife, slowly cut it out.  It will probably come away in large chunks – a very satisfying experience!

This is the moment of truth! Get yourself a bucket and start to excavate the sand from within the oven layer. Don’t forget to keep the sand for later clay-sand layers. Hopefully you will be able to excavate the sand until you reach the newspaper layer on the inside of your oven without the dome collapsing.  Take it nice n slow but I’m sure you’ll be absolutely fine.  Remove as much newspaper as you can but don’t worry too much because it’ll burn off anyway the first time you fire the oven.

Firing the oven

Kindling burning in the entrance to the oven.

Kindling burning in the entrance to the oven.

Next you need to dry your oven layer.  If you are lucky enough it will dry nicely over a few days in direct sun. However you should also fire the oven at least once to help the drying process but also to check the entrance is high enough to allow smoke to escape (see below).

The method for firing the oven is quite simple but do bear in mind that at this stage the oven will be rather damp and does not have a chimney so you might find it takes a little bit of perseverance to get the fire going. This is how I do it:

  1. Prepare some nice “pencils” of kindling.
  2. Scrunch up five or six pages of newspaper into balls and form into a rough pyramid inside but near the entrance to your oven.
  3. Build up kindling around the newspaper as if building a wigwam.
  4. Light the paper and hopefully the kindling will soon ignite.
  5. Watch the fire closely and keep slowly adding more and more kindling until it starts to burn well.
  6. At this point, using a spade, metal rake or even a bakers peel, slowly push the fire back a little into the oven.  Don’t push it too far because it is likely to go out.
  7. Add more wood and when it is burning fiercely move it back some more.  Eventually you want the fire to be burning in the centre-back part of the oven.
Fire blazing with dry patches appearing on the outside of the oven.

Fire blazing. Note dry patches appearing on the outside of the oven.

A couple of tips here.  Firstly, take it slowly. If you try to move things along too quickly you are likely to extinguish the fire.  If it looks like it is going out, screw-up a few balls of newspaper and throw them in. This is usually enough to re-kindle the blaze.  Secondly don’t use large chunks of wood  – smaller pieces burn better.

At this point you can modify the height of the oven entrance if you need to.  Look carefully at how the smoke is moving.  If it is “pooling” inside the top of the oven you need to cut your entrance higher to allow the smoke to escape.

As the oven dries it will steam and might produce a few cracks.  Don’t panic!  Fill in any cracks with spare sand-clay mixture before you move on.

Building the Brick Arch

Now the oven layer is dry you can build the extension to the entrance.  Extending the oven entrance with bricks not only looks nice but it also protects the entrance from knocks.  

Simply build a sand former in the newly cut arch of your oven, extending forwards about one brick length. Place a brick either side of the former on the top of the plinth using some of the sand-clay mix as mortar to hold them in place.  Gradually build up the archway around the former using more of the “mortar” mix between bricks.  You might have to use quite a lot of “mortar” in order to produce the correct curve for the arch (as you can see in my photographs below).  The last brick should form the keystone of the arch.  Leave the “mortar” to dry a little then remove the sand former. Hey presto – a perfect arch!

The Chimney

You need to cut a circular hole in the top of your oven just behind the brick arch entrance.  I sketched a rough circle on the top with a pencil then drilled holes around the circumference in order to help with removal of the now solid “cement”.  Just tidy the edges up a little with a knife then build-up a small 20cm chimney around the hole using more sand-clay mixture.  Finally, close any gaps between the brick arch, the oven entrance and the chimney using the remaining sand-clay mixture. 

Entrance and Chimney done!  Leave it to dry before we move onto the next stage – the insulation layer.

Brick arch and chimney complete.

Brick arch and chimney complete.

The brick arch and chimney from the front.

The brick arch and chimney from the front.

113 thoughts on “5. The Oven Entrance and Chimney

  1. Simon, exactly how do you “build” the chimney, just with your hands? I just finished the first layer, and tomorrow i’ll be cutting the door out and removing the sand. I think I’ll be ok with making the entrance but am hesitant about the chimney. Also you say cut a circular hole but your chimney looks rectangular. I’m thinking it’s going to be rather tough to make a shape like that out of the clay.

    Once again, thanks for all the help.

    • HI Peter

      yes, with your hands. Cut a hole in the top, just behind the entrance and brick arch (it may intersect with the entrance). It doesn’t have to be perfectly circular of course. I’d aim for something between 20-25 cm diameter. Once you have cut the hole, start to build up walls around it using clay:sand “bricks”, as you did the layer 1. Make sure you make the chimney thick because otherwise it’ll be really fragile. I normally overlap it onto the back of the brick arch. Also, build it tall enough to accommodate (i.e stick up above) the next two layers of oven (the insulation layer and the final layer).

      Here’s a cpl of sketches which might help:


  2. Hi Simon,
    We’ve got this far on our oven build, but the day after we finished the arch and chimney we had a bit of storm and it’s got a bit wet and cracks are forming – How worried should we be about this? Is it ok get it to dry out and then we can patch with more clay mixture?

  3. Hi Simon
    Is there any problem using a galvanised metal flue pipe from a Boiler? My thinking is position the pipe and use it as a form and build clay round it but leave the pipe in permanent?

    Regards

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