4. The Dome Sand-former and First (Oven) Layer

Finally it is time to start building your oven. For this stage you’ll need:

  • Builders sand
  • Old newspapers
  • Water
  • Tape measure or long steel ruler
  • Clay-sand mixture

You are going to build a large sand dome – the former which supports the first clay-sand layer of your oven. I really enjoyed this part of the process mainly because it provided a practical justification for the hours I spent building sandcastles on the beach with my stepson Thom when he was a little lad (to be fair it was usually me who wanted to build the sandcastles!).

Sand dome partly covered with wet newspaper.

Sand dome partly covered with wet newspaper.

Tip lots of sand onto the brick floor of your oven.  I’m not sure how many bags I used but I remember being amazed at how much was needed to build up the dome to the required dimensions.  Remeber the outside of this dome will form the inside dimensions of your finished oven.  The base (widest part) of my oven is the same dimensions as the length and width of the brick floor (80x80cm).  I decided to make the height of my oven approximately half that of the diameter (40-45cm). Build up the dome, moulding and sculpting with your hands until it is the desired height and a nice shape.  A top tip from Steve at River Cottage HQ is to keep checking the shape of the dome from above, so periodically stand on your plinth to get that birds-eye view! Once you are happy with the shape, firm-down the sand with your hands.

Sand former covered with newspaper

Sand former covered with newspaper

Next you need to add a layer of wet newspaper.  This makes removal of the sand from inside the cavity much easier later on.  It is a little tricky to get the paper to stick but persevere and you’ll crack it.  Thats the dome complete. Now you are ready for your first oven layer.

The First (Oven) Layer

If you are doing this alone make sure you leave 3 or 4 hours to build your first oven layer.  I made the mistake of starting in the early evening and ended up finishing it at midnight wearing a head-torch!

Take some of the clay-sand mixture from your wheelbarrow in cupped hands and form it into an elongated/rounded brick shape.  Press this first “brick” against the  base of the dome and compress it into place, with one hand holding it against the sand former while the other makes a “karate-chop” type movement (using a straight hand) against the “domeward” side of the brick. This creates a wedge-shaped “brick” (sloping towards the dome) which helps when adding layers above and also removes any air bubbles from the mixture which may subsequently expand and crack the oven. You are aiming for an oven layer that is approximately 7cm thick and the simplest way to keep check of this is to measure the bricks periodically against a marked stick or even a piece of straw.  Add another “brick” next to the previous one and, using the same technique, mold it into the first.  Repeat the process until you have laid “bricks” around the whole circumference of the dome.

First few "bricks" of clay-sand oven layer.

First few "brick" layers.

Begin laying “bricks” on top of this first layer and continue, round and round, up and up, until you have completely covered the sand dome former.  Remember to keep checking the oven layer thickness as you go. Don’t worry if you end up with some variation in thickness – as you build the oven layer up you might find that the base widens out a little from the weight of “bricks” above.  Smooth and shape the oven layer into a neat, coherent shape and don’t forget to check from above.

That’s it!  Your first layer is complete.  You need to leave it to dry for a few hours before you cut the hole for the oven entrance – which I’ll discuss next.

The oven layer is complete!

The oven layer is complete!

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33 thoughts on “4. The Dome Sand-former and First (Oven) Layer

  1. I have been wanting to build a Cornish cloam oven for years and have decided that it is to be this summer.(Last year I constructed a coracle). I shall be building it out of doors in my field and have been “fired up” by your web site. Are you able to help me to source a suitable clay? To heat the oven “furze” is used (dried gorse) I have to say I do not relish the cutting,preparing and storing of this prickly plant but there is plenty of it and this is what we “belong to do” in Cornwall – so as an (old) Cornish maid I have no option. When I become proficient I hope to cook a few Cornish pasties – but it will be difficult to open the oven door and just have a look to see how they are “getting along”!

    • Dried gorse sounds like an excellent fuel I have to say. I can’t really help with a local supply of clay. You could order some Potters clay online but ideally you need to find a location where you can dig your own. Look for ponds, marshy areas, river banks. Architects and builders often now where land is underlain by clay and gardeners of course!

  2. Just another novice question! Somewhere, long ago, I heard about building a willow basket as a former for the dome. Having just completed the biggest basket of my life (about 80 cm in diameter) I am now prepared to sacrifice it to the baker (my wife).
    Do you think it would work or would the interior of the oven be too uneven?
    Any thoughts, suggestions, insights or links would be most welcome.

    • You can use a basket former. You just build the layers around it and, when you first fire the oven, it burns away (sad really). I have never built one of these ovens though but there are other tutorials online to help.

      Best of luck

      Simon

  3. Hi,
    Just at the former creation stage of my oven and thought it might be a useful piece of info for others to know that it requires a good seven 25kg bags of sand to shape a 80cm dome.

    • Yes Geoffers I remember being amazed at how much sand the dome takes. Don’t forget that you’ll use all of that in layer 3 of the oven though so it won’r be wasted.

      Photos would be great when you have done.

      Best of luck

      Simon

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  5. Hi- I’m gearing up to build an earth oven and read your plans with interest. One “feels pretty stupid but better check” question: when you make the sand dome you need to mix sand with water right?

    Also, I am considering making it totally out of earthenware clay and bisking it in a kiln.
    Do you know why this would or wouldn’t be a good idea?

    Thanks,
    Verna

    • Hi Verna. The sand I was using was pretty moist straight out of the bag so I didn’t add any more water to it. It needs to be “sand castle” consistency so that it holds it’s shape while you build the first layer.

      Cheers

      Simon

  6. Hi Simon,
    got my first layer done, but think its to thin, can i add to this with more sand/clay mix, or can i just fire then add a really thick insulation layer ?
    Resent this….wasn’t sure if you got first message…? Thanks Kat

    • Hi Kat

      Apologies for the delay in responding. I managed to kill my router at home this weekend by dropping it! My worry is that the first layer is the crucial one. This is the inside of your oven and is obviously therefore in direct contact with the fire/heat. It might be absolutely fine but my worry would be cracking and it falling apart from the inside. Also, there is a danger that the layer might fall apart when you remove the sand dome former. Really you should aim for layers which are about 8cm thick. However I recommend that you do one of two things. Firstly, if the layer has NOT been fired yet (i.e. if it is not 100% dry and you still have the sand former in place) you could add another layer of clay/sand mixture directly on to top of the first one. If you wet the outside of the first layer first it should almost merge into a single coherent layer if you pack it down well. Second option would be, as you suggested, add a slightly thicker insulation layer and complete the build as per the plans. If it holds its structural integrity I’m sure it will work just fine!

      Don’t panic though and please let me know how things go.

      Best of luck

      Simon

  7. Hi Simon,
    Kat again, just put first layer on, but….I’m affraid its not thick enough, should….(or could) I put another a layer on before firing? Thickness is probably only an inch…..DUH!
    Have I screwed up?
    Thanks

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  9. Pingback: 6. The Insulation Layer « The Clay Oven

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