Completed Cast Oven

[TapRackFire]

I finally got the oven cast and we cooked a couple of pizzas in it. We had a great time. Now on to the door and insulation.

Do I make the door out of 3/16 steel and call it good or do I need to insulate it somehow? I made a temporary door out of 2" trailer timbers and it was a good fit. My fear is the wood door will burn up. Can somebody please direct me on the completion of the door?

Next question I have is the insulation ontop of the oven. Can I skip the blanket and layer on extra vermiculite & portland (at least a 6:1 ratio) ontop and around the oven. Or does the blanket play a vital role in creating my thermal mass?

Thanks again for all the help,

Tap

[brickie in oz]

Re: Completed Cast Oven

Or does the blanket play a vital role in creating my thermal mass?

The blanket is an insulator .......and is a very important part of the insulation too.

[david s]

Re: Completed Cast Oven

If you skip the blanket and use vermicrete as an alternative you will have to make it double the thickness to get the same result. Don't go as rich as 6:1 as it reduces the insulation value. I find 10:1 is much better and just enough to hold the stuff in place. Because it takes so much water let the sun and wind dry it for a couple of weeks before the curing fires and stucco. The blanket is a faster way to go.

[TapRackFire]

Re: Completed Cast Oven

Brickie, sorry if I was unclear. I realize the blanket is an isulator. I was trying to go cheap and skip the blanket and just add more of the vermiculite and portland mixture.

David, can I use any type heat tolerant insulation as the blanket? I can purchase some stuff locally called "woolaroc" and use it. It is a little cheaper. Or do I need to use the blanket I have seen on this site? After the blanket is in place I planned on pouring my vermiculite and portland 4 inches thick around the walls and on the roof. Is that thick enough?

[david s]

Re: Completed Cast Oven

The normal way to go is blanket followed by vermicrete. Blanket alone does not give a very good shape as it goes a bit lumpy where folds are created. The vermicrete allows you to get back a nice spherical shape and gives a good surface to render against.

Regarding your door, steel is a good conductor and gets dangerously hot if it is uninsulated so not such a good choice IMO. A wooden door is more traditional and a better insulator, but is prone to charring, especially if put in place at too high a temp. Traditionally Italians soaked the door in a bucket of water. But eventually the door needs to be replaced, or insulate it.

[TapRackFire]

Re: Completed Cast Oven

Does the blanket only go over the top? Or does it also fit around the sides? Is 4 inches of the 10 to 1 vermiculite and Portland mixture thick enough over the blanket and on the sides?

The door. Could I build the door out of 2 inch thick timbers and skin it with 3/16 steel to protect the wood from charring?

[david s]

Re: Completed Cast Oven

Does the blanket only go over the top? Or does it also fit around the sides? Is 4 inches of the 10 to 1 vermiculite and Portland mixture thick enough over the blanket and on the sides?

Yes over the whole oven and 4" is plenty.

The door. Could I build the door out of 2 inch thick timbers and skin it with 3/16 steel to protect the wood from charring?

No the steel will char the wood, you need an insulator.

[TapRackFire]

Re: Completed Cast Oven

Ok thanks. What do you use as an insulator between the steel and the fire?

[david s]

Re: Completed Cast Oven

I use a wooden door with a safe fibre mill board insulation panel.

[TapRackFire]

Re: Completed Cast Oven

Sounds good, but I don't know what fibre mill board is. Would that be something like concert backer board?

[david s]

Re: Completed Cast Oven

Sounds good, but I don't know what fibre mill board is. Would that be something like concert backer board?

Mill board is an insulator used in the refractory industry, don't know what concert backer board is. Some folk report success with aerated concrete, but it didn't work for me, just cracked in the middle.

[TapRackFire]

Re: Completed Cast Oven

Thanks for the help David. I found the fiber mill board on line. I will try to find some locally. When I put the ceramic blanket on the oven do I put it on the side walls as well or is it mean primarily for the roof?

[david s]

Re: Completed Cast Oven

When I put the ceramic blanket on the oven do I put it on the side walls as well or is it mean primarily for the roof?

Cover the whole dome sides and walls.

[Jaronimo]

Re: Completed Cast Oven

I used batts of fireproof insulation I found at a local builders supply. It is rated to 2,500 degrees and in the demos they show it in direct contact with a flame for 60 minutes and it still holds up. I used the batts, bent some wire to hold it in contact with the dome, then filled everything in with vermiculite.

Check the pics on my build post. It seems to be doing just fine. Even after my "too hot" cook on Sunday. Got a little overzealous when adding wood and had the oven floor at 950 degrees. Which, in case you are interested, burns the pizzas in less than 10 seconds. So as a pizza amateur, I will have to give my bit of hard earned knowledge, 950 is too hot to cook pizzas!

[david s]

Re: Completed Cast Oven

Old Italian trick- cast some semolina into the middle of the floor after you've blown or swept the ash away. It should turn black in 3 secs. 2 secs= too hot, 4 secs = not hot enough. If it is too hot I place the first pizza closer to the oven opening where it will be cooler.