FAQ

I intend to post questions and answers to some of the most commonly asked questions raised by visitors to the blog.  If you want to ask anything or suggest alternative answers please use the comments section below.

Pizza cooking with fire burning ar rear.

Pizza cooking with fire burning ar rear.

How is the ovens temperature controlled?
Temperature adjustment is very primitive. The oven reaches maximum temperature after about 3 hours of firing. I am waiting to buy a temperature gauge but have been told that the ovens ambient temperature can reach up to approximately 450 degrees C (and the brick floor even hotter). I know it gets hot enough to cook pizzas in 30 seconds (and singe the front of my hair off every time I fire it!). If I am cooking pizzas or bread then I keep a small fire burning in the back to keep the temperature up although it does drop after the initial firing (after an hour or so pizzas will take 1 to 1.5 minutes to cook!)  If you wanted to cook meat it would scorch at these high temps so the best method is to scrape the embers out, wrap the meat in foil, pop in roasting tin then whack her in the oven. If you then block the chimney and door opening you can apparently leave it overnight (or for several hours) to slow cook as the oven temperature decreases. You would then probably finish it off by browning in a conventional oven, on a BBQ or firing up the clay oven again and popping the joint back in, uncovered for a few minutes.

What type of clay should I use?
I have had quite a few questions about the type of clay to use.  As far as I know you can use any type of clay you can get your hands on.  I dug my clay from a local farmer’s field here in Hampshire (clay overlying Upper Cretaceous chalk if you are geologically minded – maybe Paleogene?).  The team at River Cottage get theirs from a pond on site, in Dorset (I think it is Blue Lias).  If you can’t find any clay locally you could always buy potters clay which would be wonderfully homogeneous – free from large particulate matter.  Which reminds me, try to get clay does not contain too many stones – they are liable to form the focus of cracks in your oven if left in the mixture.

Why is the plinth made of wood?  Surely it will burn!

I chose to use wood for the plinth for two reasons.  Firstly, I am really awful at building anything with bricks so the method I chose was easy for me.  Secondly, the team at River Cottage HQ built their plinths using the same method and, if its good enough for them, its good enough for me.

In practice the plinth does not burn (much!).  If you look at the building the plinth and oven base episode of my blog you will see that the fire (heat)  does not come into contact with the wooden part of the plinth.  The fire burns on the brick floor of the oven which is encased within the top of the wooden plinth box.  The wood does char a little at the entrance to the oven but not so much that it will cause a major problem and you can always fix a heat proof tile there if you like.

At the end of the day its more of a practical (in terms of your construction skills) and aesthetic decision.

Is it possible to use a cement mixer to mix the clay/sand?

Unfortunately it seems the answer is not really!  Lyndsey, a clayoven blog friend and fellow oven builder, recently tried the cement mixer technique but unfotunately it didn’t work.  I liked his analogy which illustrates the problem:

“its very much like making pastry, with the clay being the ‘fat’ and the sand the ‘flour’.”

However, another blog visitor did get the cement mixer idea to work by firstly drying the clay, powdering it, adding it to sand in mixer then adding water.  This to me seems like a rather long winded method though unless you have dried, powdered clay at hand!

I think you really do need to work the mixture and it seems puddling is the only way folks!  I’d love someone to show me another way if there is one.

Where can I get clay from?

It seems that some of you are having problems sourcing clay.  Ideally you will discover a free source.  I managed to find a mound dumped in a local field by a local farmer but you’ll need to do some research and asking around in order to achieve this (luckily I have one of those freinds who can get hold of anhything!).  Local garden centres might know where you can find clay because gardeners are obsessed with clay soils! Do you know of any local aggregate or brick making companies? Would the local council be able to help? Local geological societies or organisations? Geotechnical engineering companies? Construction firms (partic. ground workers)? Local architects?  If you live near any ponds, brooks, rivers or streams you might find clay there but Of course it depends very much on your geographical location.  If the local geology has been kind, you will find clay but some areas will be clay deficient.  The UK has pretty extensive clay coverage due to it’s history of numerous iceages and marine transgressions (I knew my geology degree would come in handy one day!).  Here is a website with lots of geological maps of the UK if you are that way inclined:

http://www.soton.ac.uk/~imw/Geology-Britain.htm

If you can’t find clay locally then you’ll have to buy some.  One obvious source is potters clay.  I have no expereince buying potters clay but please read this post from Nic, one of my blog vistors:

“I emailed a potters in fordingbridge, they said to me i needed a clay with a good amount of grog or molochite in, this helps give it strength for such a large item. They also suggest either P1480 Earthstone Handbuild clay or the P1484 Earthstone Crank clay (both have 20% coarse). The Handbuild clay starts at £11.39 per 12.5kg bag and the crank starts at £6.96 per 12.5 kg bag. Clay is sold on a sliding scale so the more you buy in one go the base price goes down. in another email to me they said it looks like a teracotta clay B103 grogged terracotta wold be good and I could use less sand as there is already 10% grog added to the clay, they think an oven the size of yours would take 3 or 4 12.5kg bags at a cost of £22.54. The shop http://www.briarwheels.co.uk are very impressed with your link and are telling people about it.”

PLEASE NOTE THIS POST FROM JOHN RE. VOLUMES:

Just a follow on to Nic’s note above re buying clay. I have done so but the amounts mentioned will not build an oven your size. So far I’ve used 125kg of clay ie 10 bags and reckon for my last layer will need another 3 or 4 given what I have remaining. Best be realistic and forewarned.”

You can also purchase clay from here: http://www.angliaclaysupplies.co.uk.


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150 thoughts on “FAQ

  1. Hi Simon, Over the summer my children and i built a somewhat portable oven using reclaimed items such as a stainless catering trolley (no wheels sadly), heat bricks and clay that I had left over from ceramic projects. We’re really pleased with it and your ebook was invaluable, thank you. However we lit it last night to continue the drying process before I add some free mosaic tiles I have been given and it smoked out of the door quite badly. The chimney is about 2 inches above the dome so do you know if raising the chimney would solve the problem? We are so pleased with our efforts but getting a face-full of smoke when it’s lit will temper the enjoyment I think!

    • Hi Bridget

      apologies for the delay in responding. A couple of things:

      1. The chimney may be too narrow or not positioned correctly. A photo and some measurements might help me to make an assessment.
      2. The amount of smoke definitely reduces as the ovens get hotter. Are you following my lighting instructions?

      Best wishes

      Simon

  2. I built mine with 2 inches of native clay over which I put a two inch thick layer of concrete. After a dozen firings there has been no problem with cracking.

    If I could figure out how to post photos I will send some.

  3. Hi Simon,
    Love your blog and instructions. They have been so useful. We have our first clay / sand layer complete, front arch built and chimney in. Scooped some of the sand out and lit our first small fire today. I think I’m sorted for the insulation layer, but was wondering about layer 3. Was considering trying a weatherproof layer of concrete render?? Have you ever come across anyone doing the same? I’d rather not put a roof on, but I’m in Rainy Northern Ireland!

    • HI Nikki

      I have no experience of adding a concrete outer layer. If you do, be sure to think about what you’ll use for the chimney.Let is know how you get on.

      Simon

  4. Just baked half a dozen pizza’s in my clay lined oven and they were outstanding. The oven is built on a concrete layer. I have 6×6 inch clay tiles that I beat on the sides of the oven. When the oven and tiles are up to temp I move the ashes away and slide in a metal tray on which I put the tiles. This method 1) eliminates the need to sweep ashes from the oven floor and 2) allows me to wash the tiles after they cool and 3) makes sure the floor is hot for a crisp pizza bottom.
    There has been no evidence of damage to the floor of the oven. No need to buy special bricks.

  5. Hi, just about to complete the base for my clay oven, I’ve bought the ebook and am grateful for the guidance so far. With regards the base insulation I’m using bottles topped by the brick oven base. This is the bit I’m beating myself up about. I was gonna opt for fire brick but sourcing them for the amounts I need (about 40) and not paying through the nose is proving hard. Are common or garden new house bricks (eg London Bricks available B&Q) actually up to the task?? Alot of the other blogs/website reckon that the heat wont be sufficient enough for that all important crisp base. Help please!!!!!!!

    • London bricks work perfectly. That’s what I used and I have never had any problems. Just make sure you pick ones that don’t have any cracks (some types of brick are more “cracky” than others!).

  6. Hi there, hoping to make an oven and just reading the blog and book. Trying to work out position I’d have it in and was wondering how hot the outside of the oven gets as I have a privet hedge that it would look quite good in front of but not sure whether it would ruin/set fire to the hedge.

  7. I read a lot of questions/concerns about the clay/sand mixture. One simple way of determining the ratio of sand in a native clay sample is to dissolve a representative volume of clay in water. Put the mixture in a glass (preferably straight sided for accuracy) stir and then let it settle. The sand will settle first followed by silt, and then clay. The divisions between these three types of material will not be precise but you should be able to get a general sense of how much of each of the three sizes are in your clay. It is very possible that you have enough sand in your clay as it is dug from the ground.

    • This reminds me of my days as a Geology undergraduate. Nice! One thing to note though, unless you manage to find a mixture with a ratio of at least 2:1, sand:clay (or probably nearer 2.5:1), it won’t be of any use for building these ovens. Too much clay and it will crack catastrophically.

      Simon

  8. Hi, great booklet. I will be building oven in India and have problem with fire bricks,
    can the floor be made with the same clay/sand mix as the dome?

    • No Gerry but you don’t need fire bricks. Any traditional house brick (builders brick) will do fine. Just check that they don’t have any obvious cracking potential. If not, people have used thick slabs of stone.

      Simon

  9. Hi,

    I have recently finished building my own clay dome oven and seem to be having some issues getting the oven hot enough. Having spoke to others that have also built there own oven the only thing i can think of is that either the openng size is too large or the location of the flue is wrong. could this be the issue?

    regards

    andrew

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