28" Oven in Seattle

[david s]

If cost is a major issue the use of either perlite or vermiculite mixed with portland cement to create what we call vermicrete, is an alternative. The underfloor mix should not be leaner than a 5:1 mix and the over the dome mix should be around 10:1. There drawback is that because water is added to the mix it requires considerable drying after it has been placed before building over it. See the attached table for strengths and insulation values for different strength mixes.

Note: The thermal insulation value is a function of bulk density and particle size; generally the lighter the mix the greater the thermal insulation will be. When the same volume of different grades of exfoliated vermiculite are incorporated into a standard mix, the final density (and therefore, the thermal insulation) will be influenced by the fact that the finer grade of the vermiculite used the denser the product will be. Conversely, a mix based on coarse and mid-sized exfoliated vermiculite will generally have the same thermal insulation value at ambient temperatures, but, at elevated temperatures the finer particle size aggregate concrete will be more insulating due to a lower thermal diffusion.

For vermicrete mixes I use a 50/50 (by volume) mix mixture of fine vermiculite and medium perlite for the above reason. It also makes up a more workable mix to apply, particularly useful in the leaner mix proportions.

[JBA]

I've never heard of them but I bet if you ask them for densities and compressive strength data they could probably send you some. I'm attaching the spec sheets for the board and blanket I used just to give you something to compare to if they do send you some data. I've seen recommended minimums for both here on the forum (I think from Russell or Joe) but can't remember what they are.
Did you check with the folks in Kent I had recommended in an earlier post?
Just noticed the Simond folks are showing free shipping! That could really be a deal maker depending on specs.

Thanks for the spec sheets! I will make sure that the ones I found are up to par before I order.

Unfortunately it looks like the store/business in Kent is no longer there. There used to be a Harbison-Walker in Kent from what I've gathered but the closest one now is near Portland. A little too far for me. I may search for other local businesses in Seattle that carry ceramic fiber board, but the options I've seen so far are very expensive and probably of much higher spec than what I need.

[JRPizza]

I've never heard of them but I bet if you ask them for densities and compressive strength data they could probably send you some. I'm attaching the spec sheets for the board and blanket I used just to give you something to compare to if they do send you some data. I've seen recommended minimums for both here on the forum (I think from Russell or Joe) but can't remember what they are.
Did you check with the folks in Kent I had recommended in an earlier post?
Just noticed the Simond folks are showing free shipping! That could really be a deal maker depending on specs.

[fox]

No I dont have any experience but it looks and sounds just like any other ceramic board however they do not quote the Density, the one that I use is 300kg/m³.
On a side note it seems to me that ceramic fibre is very expensive in America, I pay about half of that in the UK so I dont know if the one you have linked is good value?

[JBA]

Does anyone in here have experience with ceramic fiber board from Simond Store?

I'm looking at this

It's much cheaper than other alternatives that I've found online and locally, but it really makes me wonder if the quality is up to par.

[JBA]

Thank you all for the helpful replies!

JRPizza: I called Mutual Materials and they had fireclay! Thanks for the tip.

Latest progress includes the hearth being finished. Came out pretty good I think considering this is the first project I've worked on that includes pouring concrete. Next up I will revisit my oven design with a few minor updates and prep for building the dome starting second half of June I hope.

[JRPizza]

I got my fireclay at Mutual Materials - they have a store in South Seattle. Got my bricks from them too.

[UtahBeehiver]

You need to go to a masonary/brick supplier for brickie clay. HC Muddox is a brand available in the US and inexpensive.

[david s]

You can search also for Bricklayers Clay. If that draws a blank try Ball Clay from pottery or ceramics suppliers. Some folk have just used fine sand as a leveller. I think the clay/ sand mix produces less movement under the bricks because the clay, being finer , fills the spaces between the grains of sand.

[JBA]

On the topic of fire clay - does it go by any other name? I am unable to find any at the big box stores (Lowe's and Home Depot) in Seattle. Worst case, I might have to settle for refractory mortar mix which is more expensive.

When setting the floor of the oven on top of the CalSil insulation board the Forno Bravo guide suggests using a mix of sand and fire clay under the floor bricks. Is there any other combination of materials that would work in the absence of fire clay?

[JBA]

More progress on the oven from the past two weekends.

Stand is complete and the mold for the hearth has been completed. Awaiting a nice day without rain to mix and pour the concrete for the hearth. After that the fun part of building the actual oven component can begin!

[NCMan]

Thank you for the tips and advice!

In the inevitable event that the oven does get wet from rain or high winter humidity, do I just have to go through a drying procedure again? Say in preparation for first cook in spring after a long and wet winter.

It's always a good idea to slowly dry out an oven that has been sitting awhile, so yes. I wouldn't say you'd have to go through the whole original process, but it wouldn't hurt, especially w/your concerns/conditions.

[Pizzarotic]

do I just have to go through a drying procedure again?

Probably not that extreme. As you oven will be waterproof any water ingress will likely be in the floor insulation mainly. Run a fire for a day then close the oven and let it cool over a few days and you should be fine after that.

Nice job though

[JBA]

Building of the stand is underway!

I already have a concrete slab where I want the oven but decided to pour another 2-3" of reinforced concrete to make it level. On top of that I have dry stacked concrete blocks. Still need another angle iron - Lowe's only had one left near me.

Looking forward to pouring concrete into the blocks this weekend if weather permits.

[JBA]

Thank you for the tips and advice!

In the inevitable event that the oven does get wet from rain or high winter humidity, do I just have to go through a drying procedure again? Say in preparation for first cook in spring after a long and wet winter.