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  #11  
Old 09-11-2008, 09:55 AM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 777
Default Re: starting my clay oven.....................or maybe not.

"I would still need a 20mm layer of sand above the perlite/cement mixture though as a bed for the clay pavers/bricks. Would this still be OK?"

I would suggest that you reduce this layer to 6mm. I know it seems counter intuitive but vermiculite/cement (commonly referred to as vermicrete on this forum) is more than adequate to support the clay pavers/bricks. The layer of sand would only be for leveling the pavers and one if one follows the "directions" one would mix this sand with fireclay.

I mixed my vermicrete using a 10 to 1 mix/ratio of vermiculite to cement and it is plenty strong. And more is better regarding thickness, if you could accommodate the extra thickness 15 cm is better than the recommended 10cm (OK for the purists 102 mm); the thing is more insulation is better and unless you are going to be baking multiple batches of bread you don't really need the extra heat sink.

But Hey, it's your oven do as you want. The forum is full of good advice much of it learned by doing and as a result finding out what worked and what didn't and what could have been done differently to make a better end product. One of the mantras here is: insulate, insulate, insulate, if you cannot afford high tech, that's fine then use low tech and just use more of it.

And for me one of the great things about this forum is the freedom to ask about weird building ideas and not be flamed for suggesting something that might be heretic. And also the maturity of the members who say "I did this and would advise anyone else thing of doing the same thing to perhaps think again 'cause it didn't work for me."

Wiley
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  #12  
Old 09-11-2008, 06:30 PM
Serf
 
Join Date: Sep 2008
Location: Perth, Australia
Posts: 18
Default Re: starting my clay oven.....................or maybe not.

That's it.

I think Wiley has hit the nail on the head for me.

I have about 6" to build up to my floor level, so I will go for the vermicrete, with a minimal layer of brickies sand just to level/bed the pavers in.

Your help and advice is very much appreciated. THANKS!
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  #13  
Old 09-13-2008, 06:08 PM
Serf
 
Join Date: Aug 2008
Location: Australia
Posts: 2
Default Re: starting my clay oven.....................or maybe not.

Mickey-t,

I have just finished building the "low tech" clay oven from "better homes and gardens "and it works just fine . Cooks pizza in a couple of minutes, and holds the heat well.

I did modify the design slightly as follows;


I didn't use the granite mix on the base , but used the perlite mix for insulating properties.


When making the clay dome I added extra "Sisal" to the mix to assist in the prevention of cracking, as I have a friend who had built one using the same design and he had some cracks in his dome.- Seems to have worked as their is no cracking at all in my oven

I wrapped the clay dome with some industrial type fibre glass, covered this in chicken wire and then added the perlite insulating layer. By the way the addition of the clay to the perlite mix helps to make it "sticky" and a lot easier to work with than just cement , so don't be too concerned when laying the base that the perlite mix will be difficult to work with. The extra cost of the insulation is worth it.


I then made up some waterproof render mix and finished the outside. This is not in the design but it makes the oven weather proof.

The other piece of advice is to follow the instructions on curing the oven. Being of clay design their is plenty of water to be driven out so take it slowly.

Feel free to ask any other questions.
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  #14  
Old 09-13-2008, 11:35 PM
Serf
 
Join Date: Sep 2008
Location: Perth, Australia
Posts: 18
Default Re: starting my clay oven.....................or maybe not.

That's great to hear somebody has succesfully built this oven.

I have got the base down (100mm layer of perlite/cement), and I have bought a metre of sisal rope, which I will use the whole amount.

Could I ask you where you sourced your clay? This is the only item I am struggling to find. I will need to use a powdered clay, as there is no natural clay in Perth.............only sand..............everywhere.

I was going to ring the brick companies to see if I could get some from them. They must have tonnes of the stuff.

I like the fibreglass/chicken wire idea, I think I will copy you there too.

Thanks for the info mate.
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  #15  
Old 09-14-2008, 12:53 AM
Serf
 
Join Date: Aug 2008
Location: Australia
Posts: 2
Default Re: starting my clay oven.....................or maybe not.

I live a couple of hours drive away from Sydney, So I was able to get the clay from a pottery supply shop. It is Known as Ball Clay , comes in 25kg bags and cost around $1/Kg. You will need 2 bags and this should give you some left over for any repair jobs eg cracks. I have one crack in the external render around the Flue.I think the reason for this is that I did not put enough fibre glass insulation around the flue.

When doing the clay, try and pick a cool day as it does tend to go off rather quickly.
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  #16  
Old 09-14-2008, 06:19 AM
Serf
 
Join Date: Sep 2008
Location: Perth, Australia
Posts: 18
Default Re: starting my clay oven.....................or maybe not.

That's good information mate.

Thank you very much.

I have three mates to help me when it comes to installing the clay, so hopefully time won't be an issue. I am the "guinnea pig" here, and they all want to install the same oven but were too scared to try it first.

Cheers

Mike
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  #17  
Old 09-24-2008, 05:30 AM
Serf
 
Join Date: Sep 2008
Location: Perth, Australia
Posts: 18
Default Re: starting my clay oven.....................or maybe not.

Well folks

I have built my oven. I laid 100mm of vermicrete, then laid pavers on an ultra thin layer of sand. We formed the clay dome last weekend, and I have just tonight installed the vermicrete insulation layer on the dome.


I was a little worried, as in haste, I added sand to the vermiculite instead of cement!!

I then went over the first layer with a proper mix. Ie: perlite, cement and clay. I am hoping that it will be OK. I will apply another thin layer tomorrow and trowel it off as smoothly as possible, then weather seal it. It will be about 4" thick.

I have been "burning in" the oven for most of the week. Started with just newspaper, then kindling, then a bit more wood. I had a fire burning in the dome for about 4 hours yesterday (small fire), and all was looking good. I will continue to burn it in all weekend and early next week.

There are a few minor cracks in the dome, (already there before firing) but I am 100% confident that it is sound. The guy that sold me the clay told me that it WOULD crack, but it isn't a problem as long as the oven is insulated.

So I am looking forward to cooking pizzas for our friends next weekend. I wanted to get it finished for my birthday on 5th October, and it is all looking good so far....

I will try to get some photos on here soon.

Thanks again for your help everyone.

Last edited by Mickey-t; 09-24-2008 at 05:55 AM.
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  #18  
Old 09-28-2008, 03:34 AM
Peasant
 
Join Date: Sep 2008
Location: Melbourne, Australia
Posts: 45
Default Re: starting my clay oven.....................or maybe not.

Quote:
Originally Posted by Ken524 View Post
That guy was showing some sort of insulating material in the first 2 stands he displayed.
That white insulating material is Hebel Blocks, which is aerated concrete and has superb insulating characteristics. I'm currently using it as my insulating base.

I'm basing my design in the "Better Homes and Gardens" WFO, but making a few changes. For example, using refractory concrete rather than clay. More expensive, but less fiddly. My outer insulating later will be vermiculite with cement fondue.

Last edited by Balthazar; 09-28-2008 at 03:38 AM.
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  #19  
Old 09-28-2008, 03:45 AM
Peasant
 
Join Date: Sep 2008
Location: Melbourne, Australia
Posts: 45
Default Re: starting my clay oven.....................or maybe not.

That film clip and associated PDF from the "Better Homes and Gardens" website says to use "brickie's sand", but in the film clip he's using washed river sand, which is a very pale grey colour. Brickie's sand contains clay is is an orangey colour I believe?
Could someone clarify this?
Thanks
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  #20  
Old 09-29-2008, 08:16 AM
Serf
 
Join Date: Sep 2008
Location: Perth, Australia
Posts: 18
Default Re: starting my clay oven.....................or maybe not.

Well,

I have cooked the first pizzas in my oven tonight, and they were GREAT!!

I thought I had removed ALL the moisture, but the very top of the dome and around the flue showed dampness as we were cooking. But, otherwise, all else was good.

The moisture was only in the insulation, and not actually in the clay. The oven reached 500*C, and pizzas were cooked in just over 2 min's.

With the left over dough, I experimented in cooking naan style bread, and it was excellent.

Overall, I am very, very happy with the oven and our friends that helped in the building process enjoyed the pizza, and are just as pleased.

I can see a busy few weeks ahead helping my mates build their ovens.

We finished cooking about 4 hours ago, and the oven is still H-O-T, so, obviously well insulated.

All is good in Perth, WA!
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