spike
New Member
Posts: 1
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Post by spike on Aug 17, 2023 12:29:33 GMT
Hello, I am constructing my own pizza oven in the garden and I am thinking about using a Refractory Concrete for the oven floor as my budget doesn't stretch to the cost of firebricks.
Does anyone have a good recipe for such a concrete and what is the recommended thickness please?
Can I also cook directly on this concrete? Thank you.
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Post by downunderdave on Aug 19, 2023 19:00:10 GMT
Hello, I am constructing my own pizza oven in the garden and I am thinking about using a Refractory Concrete for the oven floor as my budget doesn't stretch to the cost of firebricks. Does anyone have a good recipe for such a concrete and what is the recommended thickness please? Can I also cook directly on this concrete? Thank you. I’ve been down this road and my conclusion is that you are better off going for a fire brick cooking floor. My current oven which is 16 years old and gets occasional use (every two to four weeks) has a one piece cast floor made from a dense castable refractory. It has a single large crack running down the centre from the mouth to the back of the oven. This does not really affect its performance though. Most commercial ovens use loose firebricks for the floor so they can expand freely and individually. Following my first oven’s cracked floor, I redesigned the floor and made many with a two piece floor that had a tongue and groove join down the centre. I now make the floor in a similar two piece arrangement but with a firebrick top surface. This arrangement is superior, producing crispier pizza bases and the top firebrick surface is more durable due to its higher density. The problem with casting a floor is that it is never truly “fired”. The material does not get vitrified at the relatively low (500C) tservice emperatures we use. Using a refractory concrete works ok for the dome but not so good for the floor. The resin is that the floor takes a greater beating, with much faster and more uneven heating with the fire built fire on top of it. Any refractory concrete should also have burnout fibres added to reduce steam spalling. Commercial castable refractory has these already added in the mix. They melt at 160c then burn away leaving a network of mini pipes through which moisture can escape. |
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Post by albacore on Aug 21, 2023 8:29:12 GMT
My oven has a firebrick floor and personally I don't think it is the best material for the job, even though it is considered the "norm" in these parts.
What I found was that the oven floor was so hot that it burned the bases of the pizzas, so you had to let the floor cool down before cooking pizza. This is inconvenient and of course, the dome is also cooling down during this time.
The issue is that the only firebrick you can buy in the UK is high duty (high alumina content). This has a high thermal conductivity which is why the pizza bases burn - the heat keeps getting transferred through to the pizza base.
In most other countries (I'm not sure about Australia) you can buy low duty firebrick, which would solve the problem. I did a lot of searching but never found a supplier in the UK - and importing firebrick would be very expensive....
I eventually got round the problem by installing a layer of handmade terracotta floor tiles (from York Handmade Brick) on top of the firebrick, which has improved the quality of my pizzas no end. The tiles do crack with the heat, but as long as they are well packed in, this is not a major issue.
If you doubt me, look at the top quality Italian ovens; they line the floor with large terracotta tiles, eg Saputo biscotti.
I am wondering if an option for Spike is to use old reclaim pure terracotta bricks for the floor, if suitable ones could be found from a salvage yard? I've often read that they are not suitable, but I'm not so sure. It's not like most of us are firing up the oven every night...
Lance
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Post by downunderdave on Aug 21, 2023 19:33:14 GMT
My oven has a firebrick floor and personally I don't think it is the best material for the job, even though it is considered the "norm" in these parts. What I found was that the oven floor was so hot that it burned the bases of the pizzas, so you had to let the floor cool down before cooking pizza. This is inconvenient and of course, the dome is also cooling down during this time. The issue is that the only firebrick you can buy in the UK is high duty (high alumina content). This has a high thermal conductivity which is why the pizza bases burn - the heat keeps getting transferred through to the pizza base. In most other countries (I'm not sure about Australia) you can buy low duty firebrick, which would solve the problem. I did a lot of searching but never found a supplier in the UK - and importing firebrick would be very expensive.... I eventually got round the problem by installing a layer of handmade terracotta floor tiles (from York Handmade Brick) on top of the firebrick, which has improved the quality of my pizzas no end. The tiles do crack with the heat, but as long as they are well packed in, this is not a major issue. If you doubt me, look at the top quality Italian ovens; they line the floor with large terracotta tiles, eg Saputo biscotti. I am wondering if an option for Spike is to use old reclaim pure terracotta bricks for the floor, if suitable ones could be found from a salvage yard? I've often read that they are not suitable, but I'm not so sure. It's not like most of us are firing up the oven every night... Lance You are correct about the high duty bricks, not only are they very dense and therefore tend to be a bit too hot, but they’re also really hard to cut and go through diamond blades pretty fast. Medium duty bricks are the most suitable. Just as the first pancake is never the best, so too is the first pizza. The trick we employ is to cook the first one pretty much in the entry where the floor is cooler. The second and third pizzas get moved further in and the oven hits its sweet spot provided a fire is maintained on the side. The floor takes a greater beating than the dome because the fire is sitting directly on top and the heat rise is very rapid. Uneven thermal expansion is the problem here. Observation of old fireplaces reveals the unsuitability of standard solid red bricks over time, where firebricks stand up well. The same applies for an oven floor. Potters ramp up their kilns at no more than 100C/hr to avoid damage to the wares inside, but the same applies to the refractory surrounding them to a lesser extent. Oven owners typically ramp up the heat at around 300C/hr. If you want to be kind to your refractory materials, heat up slowly rather than trying to reach pizza temperature as quick as possible. |
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