Just add water!

Hey, oven lovers! This is a tiny little post to show you that the clay:sand mixture we use to build these super ovens can be recycled (or rejuvenated).

As you will see, if you read my previous post, I had to do some pretty major repairs to my oven recently. Anyone who has gone to the effort of building one of these ovens will tell you that the most tedious part of the whole process is puddling the clay:sand mixture. It is hard work and very boring so, while you are going to the bother of doing it, I recommend mixing a little more than you need and storing the extra in plastic sacks. You will use it for filling cracks and maybe, one day, to undertake more major repair work. You might also need to partially, or even wholly, remove one of the dry layers, particularly if you abuse your oven as much as I have mine. Well don’t throw that dry stuff away, and if your bagged material is dry, make sure you keep that too.

All you need to do is add some water to it, leave it for a while and, hey presto, it’s as good as new. Sweet!!

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Delicious Magazine Article

Delicious Article on WebsiteJust a bit of shameless self-promotion here. Delicious magazine have just updates their website and have made a shiny new version of the article published last year about my oven (and how to build one!).

Although it contains most of the information you’d need to build a pizza oven, the devil is in the detail, most of which can be found in my eBook (funny that!!!) 🙂

Here’s the link:

http://www.deliciousmagazine.co.uk/stories/how-to-build-a-wood-fired-pizza-oven-2/

Everything you need to build your own traditional pizza oven

IMG_0899In my book I outline the steps one should follow to build a traditional pizza oven. As a result of following these instructions, lots of people all over the world have now built their own ovens. One question I still get asked quite often is how much x do I need (where x can be clay, sand, bricks etc.). To be fair, I didn’t include lots of quantity details in the original book (new edition coming soon) because, to be totally honest, I didn’t record this information during my first build.

Anyway, at a recent build I made sure I took note of everything we used, and so here are those all important quantities and a full list of other equipment required.

NOTE: 1 bag of builders sand (approx. 15kg) fills a 15 litre bucket. 

RATIOS

Normally I prescribe a  2:1 ratio of sand to clay but this is a rule of thumb. You need to aim for a mixed material which holds firm, is not too soft (or wet) and not too dry. If it is too wet (or if there is too much clay) it will slump around the base of the layer you are building.

In the quantities outlined below I use a ratio of 2:1.5 for the first and outer layers, and a softer, clay-rich ratio mix of 1:1 for building the brick arch, the backfill and chimney, mainly because it is manipulate.
Clearly the plasticity of the mix will depend upon the moisture content of the clay and the sand you are using. The drop test* will help. I’d always err on the dry side, you can always add a little water (or more clay) if you need to.

SAND – 18 bags (approx. 270 kg)

  • 10 for the dome former
  • 4 for the first (oven) layer
  • 2 for the brick arch, backfill and chimney
  • 2 for the brick arch former
  • 7 for the final layer (you will use the sand excavated from the dome and arch formers for this final layer which means you’ll have approx. five bags leftover at the end)

CLAY – 12.5 buckets (approx. 190 kg)

  • 3 for the first (oven) layer
  • 2 for the brick arch, backfill and chimney
  • 3 for the insulation layer
  • 4.5 for the final layer

OTHER MATERIALS AND EQUPIMENT

  • 2 large bags of wood shavings
  • 36 London bricks (11 for the arch, 25 for the oven floor)
  • Water
  • Rubble / hardcore (for the plinth fill)
  • Large wooden “beams”, sleepers, logs or bricks for the plinth (this depends on how you decide to build it)
  • Cement if you are building plinth out of brick
  • Right-angled brackets and screws if constructing plinth from wood
  • Glass bottles (optional)
  • Old newspapers
  • Plastic rubble sacks
  • A bucket or two
  • A drill with plaster mixer (optional)
  • A knife

*Drop Test – Form a tennis ball sized clay:sand ball in your hands. Drop the ball onto the ground from shoulder height. If the ball explodes, the mixture is too dry, if it “splats” it is too wet. Ideally the ball should just hold together.

Cracks!

A very  quick post about cracks. Lots of people contact me in a panic about cracks appearing in the oven layer during the build. Let’s start of by saying that it is very likely that you will get some cracking – in fact this is quite normal.  It only becomes a problem if the cracks become big and penetrate right through to the inside of the oven layer. Normally I’d just say, try patching the cracks with extra material and carry on but if they are significant then it might be worth starting again! It’s your call.

Why do we get cracks though? Cracks appear when the sand:clay mixture dries out and contracts. If you mistakenly use clay only to build your oven layer you will see significant cracks appear. You should not do that! However, you can get major cracks, even if you use the correct mixture of clay and sand. This happens if the oven dries out too quickly. The trick is to allow the oven to dry slowly, naturally if possible. If the sun is blazing you can use an old trick that builders use when building walls to help slow the drying process down – cover it with a damp sack, or even a tarp.  If you do light a fire inside to help with the drying process –  keep it small and gentle.

Thanks to Mungo Finlayson, an oven builder from Scotland, who shared these photos with me. It seems that some rare Scottish sunshine dried his oven layer too quickly. I suggested Mungo should try and fill the cracks before having to resort to starting again.