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  #11  
Old 05-12-2013, 06:57 PM
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Default Re: First post, first clay oven build, first of many questions!

Quote:
Originally Posted by jonnygunit View Post
So I've been pretty busy over the weekend and the weather hasn't been cooperating but I'm happy to at least be making progress with the planning. I'm confident with how I'll be going about building/insulating my plinth and laying my oven floor!

I must admit talk of breathability, and types or mortar has me a little bit confused! Gulf, are you saying add mortar to the clay to make a more hardy thermal mass layer? Or when added would it become a material for insulating?

The main question I am left with is how to insulate my dome? I know I could mix straw with my clay to form cob and use that. Is there any reason (big difference in performance, weather resistance etc) to not simply go down that route? I liked the idea of a more modern insulation (ie. vermicrete) especially it it gave me the option to render and do away with a roof, but I'm not too keen on the idea of it being experimental!

Cheers as always

Jon
Gudday
Type in adobe into goggle ...it's basically cement /lime stabilized earth. Very common in Mexico.
I stick by my first comments .....if I was to go down the path to the pearlcrete insulation on a clay oven I would keep it "breathable" so any moisture can them escape. I have a breathable paint over my dome and a breathable sealer on the exposed brickwork on my own oven. I live in sub tropical QLD and its inportant to allow the moisture to escape as it will crack a render coat as 1 ltr of water becomes 1600 ltr of steam.

Regards dave
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  #12  
Old 05-12-2013, 07:29 PM
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Default Re: First post, first clay oven build, first of many questions!

Gudday again
There's a set of plans for an adobe oven
In this section it's called a "hybrid oven brick and clay" or something similar .
On the first page there is a one of the posts has a link to a set of plans for a "Sunset outdoor oven" I'm not saying to build this type but the plans and that thread it will increase your knowledge base.
We have had a news report here that UK is due to have another wet summer so its looks like last year again for you.
On water again this the other end of you oven its important to put a waterproofing layer under the slab another under the insulation would be good as well. No use having the moisture wicking up from the ground
Regards dave
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  #13  
Old 05-12-2013, 07:31 PM
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Default Re: First post, first clay oven build, first of many questions!

Clay, Portland cement, Hydrated lime, and sand are mixed to make a refractory (thermal mass) shell. In the states Type N mortar is 50/50 Portland cement and lime. I'm a little leery of the term clay soil. In my area, that could mean just about anything. True clay can be found deep enough under ground to be free of sticks, sand, or any organic material. In my area, that can be from 4 to 16 feet deep. The depth can vary. When wet, the clay should be very similar to the consistency of modeling clay.
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  #14  
Old 06-03-2013, 07:58 AM
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Default Re: First post, first clay oven build, first of many questions!

Summer still hasn't quite arrived here, although it is threatening and I've had a few nice days to work on my plinth. All the footings are in and the walls are slowly creeping up. Im going to incorporate an old slate from a pool table as a (rather large) countertop. Ill try to post some pictures once theres something more interesting to see.

My search for clay continues..... I found an environmental recycling place with a huuuuge pile of 'clay subsoil' sat waiting to go to landfill. I took a couple of handfuls of the freshest, clumpiest stuff for the shake test and turns out its about 50% clay. It was brown, similar in colour to topsoil. This is option 'a'. My only concern is that, because the place is basically a dumping ground, by the time I go back the stuff I tested will be buried under another 10 different soils from 10 different places.

I thought I was onto a real winner with option 'b'. A relative of a friend of mine mentioned his farm was sat on a old coal pit....... fireclay?! Me and my spade paid him a visit at the earliest opportunity. I explained to him what I was looking for and he walked me 500 yards straight to a quite boggy area in the shade of some trees, and confidently pointed at an area of grass for me to dig. My spade pierced the ground and it was like digging through modelling clay. It had rained in the morning and this earth was like light grey plasticine. There were a few stones and roots as Id expect but the other noticeable 'impurities' were chunks of coal. Everything tells me this is the good stuff, my only issue is the results of the shake test. This time the top clay layer which separated out was only 20%-25% of the total volume. I just cant believe there could be less clay in this that the basically clumpy soil of option 'a'. My hope is that option 'b' is actually 2 different types of clay which settle at different rates in the shake test so the top 2 layers (~70%-80%) are both clay. Anybody any thoughts on this? I suspect it is jus5 me telling myself what I want to hear!

How should I decide which to use? I dont have enough for a test brick of aoption a atm but I could easily go back. Im thinking of making a test brick of pure clay from option b. What should I hope to see? Lots of cracking and shrinkage if its high % clay?

Cheers all

Jon
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  #15  
Old 06-03-2013, 02:14 PM
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Default Re: First post, first clay oven build, first of many questions!

Gudday
From what I understand of the shake test . The sand and heavy materials fall to form the bottom layer the next is the clay ? And the the water at the top should contain the organic material in suspension.
Could you not seperate the materials on a bigger scale and retrieve the clay?
Just a bucket for an experiment . Fill with water at least 3 times and decant the liquid off to remove the organic material. Then let it settle so you can retrieve the clay that settled off the top of the sand. Then you have a clay that you can mix back with sand in more correct proportions.
I know its crude but it might be worth an experiment?
Regards dave
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  #16  
Old 07-17-2013, 08:05 AM
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Default Re: First post, first clay oven build, first of many questions!

howdy all. canada here. just got back from a run for clay.. had to use the boat as the claybank is at rivers edge.. very slippery trying to stand and dig and fill buckets. havent tested it yet but it looks like the blue clay. very little organic if any. I was picky when digging different spots.
I will be building the clay oven with sand and clay and the outter layer will have straw or wood shavings. working on the roof for the whole shebang rite now.

a question..
would it be benficial (insulating barrier) to leave a 1" airspace b4 the outter coating? I could fill it will vermiculite or verm mixed with masonry cement.
I have been waiting till I could find clay , to continue.. the base is 8x16" blocks and a cenemt pad was poured with 2" sand spread, then. 1/2" cement board, then 1" more of sand.. the firebricks are lid on top of that.. looks to be a bout 36" circle.

this is the first post i stopped at in this secondary forum.. good stuff ..

gord in canada
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  #17  
Old 07-17-2013, 08:37 AM
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Default Re: First post, first clay oven build, first of many questions!

I would say that you will need a insulation layer under your fire bricks, or all the heat will go south.....a heat sink. At least 4" of perlcrete or vermicrete and or a CF board would be needed.
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  #18  
Old 07-17-2013, 09:03 AM
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Default Re: First post, first clay oven build, first of many questions!

the sand, then cement board , then snad under the firebrick was for insulating.. its about 3-4" thick
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  #19  
Old 07-17-2013, 09:09 AM
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Default Re: First post, first clay oven build, first of many questions!

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Originally Posted by zeker View Post
the sand, then cement board , then snad under the firebrick was for insulating.. its about 3-4" thick
Sand is NOT an insulator!!!

Use vermicrete or Perlcrete or 50-50 mix of each, mix at about 7-1 by volume with portland cement and put down about 4 inches. This goes directly under your brick floor.
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  #20  
Old 07-17-2013, 12:39 PM
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Default Re: First post, first clay oven build, first of many questions!

ty.. its early enuf to redo..
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