Comments on: 6. The Insulation Layer

By: Shona Macdonald

Shona Macdonald — Fri, 30 Nov 2012 08:47:24 +0000

Hi Simon, THANK YOU so much for your reply, it is such a relief to know we don’t have to take it apart and start again, here’s to many summer nights around the pizza oven. Thanks again Shona

By: Simon

Simon — Wed, 28 Nov 2012 08:41:21 +0000

Hi Shona

You say you finished the insulation layer but did you also add the final (3rd) layer of clay:sand mixture? The mulch will be fine (I assume you mixed it with clay) but you’ll need the final outer layer. This will prevent the insulation from combusting because it will not oxygenated (if you know what I mean).

Does this help?

Simon
PS I did have some of my insulation layer catch fire once when I developed a rather large crack in the outer layer. I poured water on it to extinguish it then filled the crack.

By: Shona Macdonald

Shona Macdonald — Wed, 28 Nov 2012 02:17:29 +0000

Hi Simon
We have been making a clay pizza oven from the river cottage bread book, we had finished our insulation layer, and had used more of a small bark mulch which we had thought would be ok, in a few days time we lit a fire in the oven and over time the insulation layer began to smoulder and burn, are you able to tell us what went wrong, have you heard of this happening before? Look forward to hearing from you.
Shona

By: Simon

Simon — Mon, 22 Oct 2012 13:53:29 +0000

Errr…only if you could mix it thoroughly with clay – I imagine it’ll burn otherwise!

By: Dennis

Dennis — Mon, 22 Oct 2012 13:45:53 +0000

hi Simon. Can I also use rockwool as an insulation layer??

By: Simon

Simon — Fri, 08 Jun 2012 09:03:25 +0000

Glad you are having a go David. Insulating layer is just wood shavings and clay – you don’t need sand. However, you can pretty much use anything you can get your hands on as long as it has an insulating property. I know people who have used vermiculite from garden centres, straw, hay, wool. As for the ratio, it is imprecise. Make some clay slip in a large bucket (old black dustbins are good) or pour it into a wheel barrow then gradually add wood shavings until you are able to form clumps (“bricks”) from it, as you did the sand:clay mixture. If it’s too wet, it’ll just slump around the bottom of the oven, too dry and it wont stick. It will dry quite solid, sort of like a compacted flapjack texture. I would then leave it to dry naturally.

Best of luck

Simon
PS don’t forget to send us a photo for the blog (simon.brookes@gmail.com).

By: David

David — Fri, 08 Jun 2012 06:31:55 +0000

Hi Simon,
Your site inspired me to build an oven of my own. So far I’ve build first layer, it is dried now. Now I’m off to build an entrance and the chimney. I am just curious about the mixture for the insulating layer.
I’ve read the comment for James, and it showed me the general picture. However, I’m still a little curious about that mixture. Some people mentioned sand in their comments and you did not mention it in the list of required materials. Do you use it in this layer at all?
One more thing. I know you did not measure it, but about the ratio clay to wood shavings, can you at least roughly say it – is it just a bit of shavings, around equal part, or much more shavings than clay? Should this layer be firm, or is it expected that he has lots of cracks (since it’s function is just for insulation).
Oh, yeah… one other thing. Do you recommend drying this layer in the same way like you’ve dried the first one (with small fire)?
Thanks for you help.

By: dogger

dogger — Thu, 15 Jul 2010 12:04:00 +0000

hi as from my other posts i dont like the idear of wood insulation .ok my sugestion is that you use perlite (same stuff you bye at b&q in garden sectionused as plant feed ) lol ok you may laff but its got very good insulation properties (its used in construction to fire proof concrete)you can puddel it in to the clay as you do the sandit is water proof as well so mised with the clay may reduse the water damage in over wintering it also does not rot i saw it on another clay oven web site si i looked up the properties of it and i think it may be better than the wood shavings with the heat the ovens produse as with simons catching light lol

By: Simon

Simon — Thu, 15 Jul 2010 09:23:03 +0000

Well you don’t have to use wood shavings if you don’t like. All I can say is that it works! Have fun.

Simon

By: dogger

dogger — Wed, 14 Jul 2010 19:41:37 +0000

hi i have read the paper you quotied on wood shavings an i concur wood shavings are a good thermal heat barier (but and i quote the layer must be 310mm thick) thats a foot and 1 inch or there abouts wood shavings also suffer with damp if one gets wet and is touching another the prosess of osmoses becomes invilved where the water is transferd through capilary action to the next shaving this could cause a wet layer to form with in the clay next time the oven is lit after a break for winter say you are going to get a layer of steam prodused in the clay in my view causing a weak point in the oven as i said why use wood shavings