Brick oven reconstructed to a steel one

[Tscarborough]

Re: Brick oven reconstructed to a steel one

"Clear" is a measure of the surface temp, "saturate" is the temp of the entire mass being equal. The problem with using materials with different thermal coefficients of expansion is that you will never be able to maintain a direct 100% transfer of heat between them. They will separate, and that miniscule separation will tend to insulate them from each other.

[v12spirit]

Re: Brick oven reconstructed to a steel one

So. The homebrew was chosen to clad the sidewalls of the oven being more flexible. For the top of the dome, I thought of cladding with the red bricks I have. They are sold as fire bricks and all brick ovens in my region are built with them. The plan (subject to change) is to cover the top of the dome with 50.50 clay.sand, lay the cut bricks, and fill in between with the same clay/sand mix.
Is that better than three pieces of homebrew over the dome regarding:
1-maintaining a continuous conduction with the top of the dome?
2-holding heat. I mean are the red bricks better than homebrew as a thermal mass?

[Saovicente]

Re: Brick oven reconstructed to a steel one

So. The homebrew was chosen to clad the sidewalls of the oven being more flexible. For the top of the dome, I thought of cladding with the red bricks I have. They are sold as fire bricks and all brick ovens in my region are built with them. The plan (subject to change) is to cover the top of the dome with 50.50 clay.sand, lay the cut bricks, and fill in between with the same clay/sand mix.
Is that better than three pieces of homebrew over the dome regarding:
1-maintaining a continuous conduction with the top of the dome?
2-holding heat. I mean are the red bricks better than homebrew as a thermal mass?

Interesting thread....Now I understand the questions from the other thread.

I am by no way an expert, but I will provide you with my thoughts from experience with my build, which I formulated with thorough research and helpful advice from members here.

I would not use the homebrew recipe for the cladding...you have already created that "layer"with your steel oven. I would use an insulating cladding layer. I recommend one I found elsewhere to which worked well for me.

Rado's Cladding recipe 4,1,1.
4: 4 parts stone, 2 parts coarse sand. 1: portland cement. 1:lime type(S) Mix all ingredients, then slowly add water.

My thoughts are that you will need it and a layer or two of thermal blankets on top. Since the oven is made of steel, (1) Cover the entire oven with about 1/2" of your thermal blanket, (2) cover the blanket with 2 layers (foil rips easily) of aluminum foil - seal the foil parts with aluminum tape (to prevent the blanket from getting wet - Add 3" of the cladding over the entire oven.

Slowly add the mix in layers (1" at a time - Gravity will not help with the surrounding perimeter - Use a sander inside and out as you add the layers to vibrate the mix into place. The vibration will remove a lot of air pockets and provide you with a dense layer of cladding.
As I wrote on the another thread...cover with plastic and blankets for the minimum of a week ++,...more is better.

V....Give it a shot....if it does not work for you, simply chisel it away and begin anew....It is a cost effective solution or I dare say experiment. When done, you will be ready to make, break bread and tea with invited family and friends in the cooler weather to come.

[Tscarborough]

Re: Brick oven reconstructed to a steel one

Rado's cladding mix is concrete, not insulation, and will begin to fail at 500F (which will not be a problem for this application). Done as you suggest, it will also compress the blanket and degrade its insulating properties.

It should be steel>thermal mass(cladding)>insulation>protective layer of whatever.

[Saovicente]

Re: Brick oven reconstructed to a steel one

Rado's cladding mix is concrete, not insulation, and will begin to fail at 500F (which will not be a problem for this application). Done as you suggest, it will also compress the blanket and degrade its insulating properties.

It should be steel>thermal mass(cladding)>insulation>protective layer of whatever.

Absolutely not so. The mix does not and will not fail at 500F or 900F +. First off, I never wrote that it was insulation, it has insulating properties and combined with the blankets, it will provide him with the needed heat retention he cannot achieve from the steel alone, especially since the oven is an indoor environment. Secondly, the "1/2 " was not meant act as an insulator but as a buffer between the steel and the cladding.

Why would one state to add 1/2" of such product between two hardened layers for insulation. It would be cumbersome and ineffective.

For the sake of a good discussion:The blanket is stronger than it appears (it has a lot of spring to it) I have tested it out, if he adds the mix in layers and vibrates the dome as he progresses, the weight will be distributed evenly, minimizing the compression. Even if it were to compress, so be it. It would have fulfilled its intended role.

I surrounded my homebrew mix oven with 2 1/2 to 3" of cladding. I had used the oven before and after the cladding and noticed significant increase in heat retention after the additional add-on. I took the temperature to 900 + degrees on all of the occasions of using the oven and the cladding did not break off. It has been more than six months and still no issues.

[david s]

Re: Brick oven reconstructed to a steel one

Insulating blanket between the steel dome and cladding layer, while allowing the steel to expand, will not allow heat to travel via conduction to the cladding layer. This will result in a much slower heat up, quite contrary to what v12spirit wants.

[v12spirit]

Re: Brick oven reconstructed to a steel one

Thank you all for your inputs. I may be ordering cement fondue because it is surprisingly not more expensive than homebrew in my region!
Is it better to go 1:1 with sand or 1:2?
Should I cover the mix with plastic as in homebrew?
If there are any cautions regarding using fondue please tell me. I have only one 25 kg bag to suvive with.

[david s]

Re: Brick oven reconstructed to a steel one

There should be a guide on the bag. I think it is 3 parts sand 1 part ciment fondu.

Look here ...

http://cimentfondu.asia/gb/artisans/PDF/p_FAQ.pdf

[wotavidone]

Re: Brick oven reconstructed to a steel one

I was a bit concerned. No post on this thread from v12spirit for a month. For a moment there I worried that the military situation in Syria was responsible.
But I see he has posted today on another thread.
Phew!

[v12spirit]

Re: Brick oven reconstructed to a steel one

I truly appreciate it wotavidone.
Thank you.

[GianniFocaccia]

Re: Brick oven reconstructed to a steel one

Is it better to go 1:1 with sand or 1:2?
Should I cover the mix with plastic as in homebrew?
If there are any cautions regarding using fondue please tell me. I have only one 25 kg bag to survive with

The proper ratios for mortar and concrete using Ciment Fondue are listed here:

http://alag.net/gb/artisans/PDF/Guide_CF_GB_web.pdf

It says that Ciment Fondue makes an excellent refractory cement provided suitable aggregate is used. Perhaps by adding brick chips you can stretch the coverage of your single bag while adding needed thermal mass.

John

[v12spirit]

Re: Brick oven reconstructed to a steel one

G'day
50 /50 powdered clay and sand, add water to make a stiffish paste. Apply with a notched tile trowel. When you put the bricks in position the sides of the brick must first touch, then you drop them down. If you drop them down first then try and push then together your paste will build up and seperate the brick. Tap then down with a rubber mallet if not a block of wood and an ordinary hammer is just as good.
If the surfaces are drawing the moisture out of the paste a smear of margerine or cooking oil will provide a temperary barrier. Might not be needed inside out of the sun. See what happens
Regards Dave

I've cut the hearth bricks and they are ready to be laid. I have fine crushed basalt in hand; the same texture as the available silica sand. Are there any advantages for this material over sand so I may substitute it with sand in the 50/50 mix?
Edit: The hearth bricks are extremely thin; 1.8 cm thick. The powdered layer is supposed to be about 1 cm thick so it will add a sort of thermal mas.

[Greenman]

Re: Brick oven reconstructed to a steel one

Hello V12

I think your issue will be the thin bricks you have for your hearth. You will get something by way of heat retention from your bedding material but you are still very light on with the mass of the hearth. I can not suggest a way to increase the thermal mass of your hearth other than doubling up with the bricks.

Others on the forum may have a notion of how. Either that or it might not be an issue, depends on how you want to use your oven.

[v12spirit]

Re: Brick oven reconstructed to a steel one

Slowly but steadily , cut the hearth bricks and laid them on the 50/50 sand clay mixed with water. Too tiring due to oven's small size. Could have asked for help from Mrs. Pepper Pot .

[wotavidone]

Re: Brick oven reconstructed to a steel one

Slowly but steadily , cut the hearth bricks and laid them on the 50/50 sand clay mixed with water. Too tiring due to oven's small size. Could have asked for help from Mrs. Pepper Pot .

Nearly there mate, it really is starting to look like an oven.
Your wife must soon start to smile.
I had to look Mrs Pepper Pot up. How on earth does a Syrian in 2015 hear about a Norwegian children's story book character from 1956?
Or is it that everyone else has heard of her, and the story just never quite made the journey all the way to the outback of South Australia where I live.
P.S. I think your thin bricks will be OK. I've seen commercially available ovens with dense 50 mm refractory walls with 25 mm floor bricks sitting directly on ceramic blanket insulation. You have 18mm bricks on sand/clay mix on top of a layer of steel. You can't really have fast heat up and high thermal mass, and the balance of floor mass to dome mass is important.
One thing I am wondering about. We see Syria on the news nearly every night now. We never seem to see forests. How are you going to get firewood?