Dome Insulation Question

[SableSprings]

Here's another build for a barrel vault that you might find interesting...

https://community.fornobravo.com/forum/pizza-oven-design-and-installation/getting-started/19482-nw-ohio-build-opinions-welcome

Also, thinking ahead, you are going to need some support to set the red brick barrel facade in place. I used metal lath (for stucco work) but think that it would have been better to use hardware cloth which is a stiffer wire and would have been a bit more stable/supportive as I laid my half bricks into position...

A vent has been applied in lots of builds to help moisture escape from the oven and insulation...also a good idea and something to consider.

[llamabucket]

Mike, thanks so much again, I really appreciate all your help! Now on to continuing my oven!
One more thing, I've been googling and calling all my local hardware stores and I'm having an incredibly hard time finding dehydrated lime, fireclay and let along calcium aluminate or silica sand. Where does everyone buy this stuff?

[SableSprings]

Check with a business that sells concrete and paving products. They are normally oriented to builders not home diy'ers. One problem I can solve for you is that you need to be looking for hydrated lime NOT dehydrated lime. Hydrated lime is commonly sold in places like Home Depot as Type S Hydrated Mason Lime. Fireclay is something you should be able to find at a place that has supplies for making pottery. I suspect they will also have fine sand...doesn't have to be silica sand, just fine (and not builders sand). From everything I've read, working with calcium aluminate is not for us casual builders as it sets extremely quickly.

Stick with the 3 parts fine sand, 1 part Portland cement (not ready-mix concrete!), 1 part hydrated lime, and 1 part fireclay.

Did you have a chance to look at the barrel vault build link in my post #16 above...it seems to address a lot of issues similar to what you're planning.

[llamabucket]

Hey Mike! Update
So you were right! I found all what I needed at a local potter store, yay! However, hydrated lime is impossible to find. After days of searching, I finally picked this up from a nearby store:

http://www.rona.ca/en/hydrated-lime

Is that what I need? I'm reading about "Type S" lime, but this doesn't say anything about being any kind of type? Another thing the pottery guy told me is that I could buy Dolomite from him. He said it's perfectly fine to use as well...but since I see no mention of dolomite around here, I was afraid it would be wrong to buy?

[SableSprings]

I'm glad you found the stuff at the potter store. It looks to me like the Rona hydrated lime is the correct stuff. I also looked up a couple resources and found this helpful bit about Dolomite and hydrated lime.

"Builders Lime is NOT the same as Dolomite or Garden Lime and is therefore not safe for the garden. Builders lime is hydrated lime, made from limestone, from 'burnt lime' which is heated to make it more concentrated and then hydrated with water, very reactive and likely to cause root burn if you are not careful. Dolomite and Garden Lime are safe to the touch."

Did you happen to go look at the bag in Rona? I suspect in the list of uses on the back it would give you some "confirming" info...but hydrated lime is definitely what you need for the mortar. It would be good if you could contact someone in construction that was familiar with the local products and brick/mortar work. At least you'd be able to get some "professional" confirmation. Sounds like you're making progress anyway!

[llamabucket]

Thank you for that info! So, I actually bought this stuff from Rona and took a look all over the bag for any information, but unfortunately there's no hints as to what it exactly is. It only says "for household, garden and commercial use"...which is pretty broad lol!

I DID buy it from a home improvement/renovation place so I'm assuming it's used for building...but again I'm just guessing

As for the dolomite stuff, it was actually suggested by the pottery shop guy. They sell products to repair and build kilns! So I'm fairly certain it would also be used for stuff like this....but I'd love to know for sure.

[llamabucket]

So I read the back of the bag and here's what it says:

"To use as lime wash, mix 6kg with water to a creamy consistency and allow to stand 10 minutes before using. A small capful of dissolved salt added to this mixture will improve adhesion considerably. For sweetening lawn and garden soil, apply a week before or after fertilizer has been added. The recommended dosage is 24 sq. m per 6kg bag"

So I'm confused. This is both for building and garden work? It says it's an irritant and it says it's hydrated lime!

I'm glad you found the stuff at the potter store. It looks to me like the Rona hydrated lime is the correct stuff. I also looked up a couple resources and found this helpful bit about Dolomite and hydrated lime.

"Builders Lime is NOT the same as Dolomite or Garden Lime and is therefore not safe for the garden. Builders lime is hydrated lime, made from limestone, from 'burnt lime' which is heated to make it more concentrated and then hydrated with water, very reactive and likely to cause root burn if you are not careful. Dolomite and Garden Lime are safe to the touch."

Did you happen to go look at the bag in Rona? I suspect in the list of uses on the back it would give you some "confirming" info...but hydrated lime is definitely what you need for the mortar. It would be good if you could contact someone in construction that was familiar with the local products and brick/mortar work. At least you'd be able to get some "professional" confirmation. Sounds like you're making progress anyway!

[SableSprings]

Sorry not to get back to you sooner, but yes, what you have is the correct material to make the high-temp home brew mortar discussed in the forum. Hydrated lime can be used in both building and gardening...the building applications require a finer ground product (which makes it very reactive) and if you use the builders' finely ground hydrated lime as a gardening soil additive you use much less (also because it is more reactive to water ).

It is a good idea to mix your dry home brew materials together before you add water...kinda like making muffins--mix the dry ingredients first and then add the wet . Hydrated lime is definitely a skin irritant and you will want to wear protective gloves, eye protection and a dust mask when using the finely ground product. The material that's normally used as a gardening soil additive is in pellet form and not nearly as reactive (because of the pellet size and some added ingredients) and an application to the soil lasts much longer.

Hope that helps clear this muddle up a bit...