Refractory heat insulations.

Also in wood fired ovens the energy absorbed into dense firing chamber must be kept in letting it to serve it's purpose. It should vibrate only inside the dome and cook for us for a long time. If the dome wasn't covered with insulation, heat energy from the fire would quickly run away leaving the dome cold.

Dome walls of the oven are made of dense material with high thermal conductivity therefore cooking chamber is capable to soak in heat from the fire and lead it all across in the body. This heat energy also enters right the outside edge very quickly, literally in a high speed. In other words, as well as the dome is hot on the inside, very fast it gets equally hot on the outside. "That means it's loaded with cooking energy :o) 'Oh no no … don't get scared it is very good for you!!! We will just give the oven a nice coat to keep it warm even though it is not winter, and that way the energy is only ours."

Refractory heat insulation types

You can choose from many refractory insulation types. Some are packed in bags and used in a loose form by pouring it dry in around and on top of a boxed in dome of any shape. Then there are blanket form heat insulations (rolled in different lengths or precut into smaller sizes.) You can easy prepare your own mix or buy insulations that are mixed with water before application, these can be cast or built up by hand, after setting the mix forms solid but soft insulating layer.

Dry, loose form heat insulations that can be poured around and on top of boxed in dome:
Vermiculite or Perlite – both sold in different grade sizes, choose one in the middle, don't get the dust. Also sold in larger landscaping or gardening yards for horticulture. Commonly used for nice oven structures where the dome is boxed in between e.g. building brick or metal sheet walls.

Application thickness of 4” –10cm plus will do.

Ceramic fiber blankets or bats:
This option is perhaps a bit more costly but in limited space area for wood oven it will help perfectly. Sold in different grades, for wood oven you'll need lowest grade because top grades of this material can be used in stoneware high temperatures and also on the hot face (and a lot higher). If you want to use ceramic fiber you only need to place it around the walls and top, often a good grade will require only 1” – 2.5cm to 2" – 5cm width. Don't put anything heavy on top, like other layer or insulation or wet layer of mortar etc., it shouldn't be squashed down at all, the high quality of insulation would be degraded/lost (remember the honeycomb effect?) Ceramic fiber blankets should be hidden/protected behind a casing. WARNING when working with these blankets wear gloves and respiratory mask as it releases particles which many people are allergic to, watch that silicoses, not dangerous as asbestosis (asbestos awareness ← work & safety page.) Sold are also ceramic fiber insulations in form of fluff, which can be pushed into narrow areas but don't pack it too much not to hard it solid. Available in refractory or pottery supplies shops. I'll take picture of the blanket and add it in here.

Mixed refractory insulations:
13 : 1 : 1 - Vermiculite, Portland cement, Lime. Mix all dry ingredients then add small water amount in stages while mixing. This will become solid but stays soft! Used e.g. for covering of the dome e.g. into barrel or igloo effect on outside. (It is not insulating concrete or mortar.) Apply in 2.5cm – 1” layers, do 3-4 or more of them allow each layer to set before following one. Last, still insulating layer, can be thinner with double amount of cement. Finally for the weather finish, the oven can be rendered on chicken wire, just like the stucco on old wooden houses.

13 : 1 : 1 – Perlite, Portland cement, Lime. Mix all dry ingredients then add small water amount in stages while mixing. This will become solid but stays flexible! Used e.g. for covering of the dome e.g. into barrel or igloo effect on outside. (It is not insulating concrete or mortar.) Apply in 2.5cm – 1” layers, do 3-4 or more of them allow each layer to set before following one. Last, still insulating layer, can be thinner with double amount of cement. Finally for the weather finish, the oven can be rendered on chicken wire, just like the stucco on old wooden houses.

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