40" brick oven on Tasman Peninsula

[cobblerdave]

Re: 40" brick oven on Tasman Peninsula

G'day
http://www.fornobravo.com/forum/3/hi...tml#post115031
Here is a link to some "exploratory surgery" I did a few years ago.
My oven has 2 ins of ceramic then a layer of fiberglass batts over that.
The ceramic is very efficient as you can see from the readings it tempers the heat right down and protects the fiberglass from the worst heat.
I must stress though I would never use fiberglass home insulation directly on the dome it just not built to handle those high temps. The glass fibres are formed over 1200C but the plastic binders are not and there the thing that will melt and burn. There are however forms of non domestic fiberglass insulation available which are designed for 650C plus.
Regards Dave

[david s]

Re: 40" brick oven on Tasman Peninsula

Have you tested any insulation bats directly against the dome on an oven Dave? I used them on my first oven, both over the dome and under the floor (using IFB's to support the floor pieces where necessary and insulating bats in between) On dismantling the oven there was no perceptible deterioration of the fibreglass. I would not use the stuff again though, because who knows what may be released at temperatures the stuff is not designed for, but also important is that the stuffs low density makes it impossible to render against without it compressing, if you are building an igloo. I have no idea what brand I used, but it was 2" thick yellow stuff with foil glued on one side, standard roof insulation, I obtained it from a building site skip.

[cobblerdave]

Re: 40" brick oven on Tasman Peninsula

G'day Davids
No I have not tried fibreglass directly against the dome but I did try to give it a heat test with a gas blowtorch which it came through well. I then tried an oxy torch. It does melt and it does give off fumes, but this is a massive amount of heat concentrated on a small area. This is why I'm cautious and always recommend it as a second layer of insulation as I have done.
I was influenced in using fiberglass ( read term rockwool) and hebel from this build. As I had a set budget which I blew on firebrick and ceramic insulation I had to make it up in other ways

http://www.fornobravo.com/forum/f43/...dah-12821.html

Like you said it does compress a bit but I was using 3.2R big thick batts with a goodly layer of birdwire on top it held up the render coat really well.
It served me well and I was able to get the dome rendered in with dry insulation. If I had used pearlite it would not have dried for months considering the rains we had that year.

[stonecutter]

Re: 40" brick oven on Tasman Peninsula

G'day Davids
No I have not tried fibreglass directly against the dome but I did try to give it a heat test with a gas blowtorch which it came through well. I then tried an oxy torch. It does melt and it does give off fumes, but this is a massive amount of heat concentrated on a small area. This is why I'm cautious and always recommend it as a second layer of insulation as I have done.
I was influenced in using fiberglass ( read term rockwool) and hebel from this build.

Dave, rock wool (mineral,wool) and fiberglass are not the same thing. Fiberglass does contain organic binders that break down at high temps. And though it my resist high temps for a short time, it is not designed for continuous high heat exposure.

[Greenman]

Re: 40" brick oven on Tasman Peninsula

Given the huge price differential between ceramic fibre insulation and the fibreglass (in this country at least) it would be interesting to know if the temperature that would exist on the outside of 1" of c/f insulation would be enough to degrade the fibreglass insulation that is commonly used in building.

The builders with plenty of room for insulation may be able to save some $$ if the two materials can compliment each other.

Any wisdom gents?

[cobblerdave]

Re: 40" brick oven on Tasman Peninsula

G'day Steve
Check out the link in my post no 46 for readings
For standard fiberglass insulation read domestic fiberglass regardless of if its marked rockwool or mineral wool in Aust
However there are industrial versions of fiberglass insulation available that are made to take 650C and above that would be suitable for ovens. The last time I checked they were made by CSR and were a third cheaper than ceramic blanket.
Regards dave

[Greenman]

Re: 40" brick oven on Tasman Peninsula

Thanks Dave - handy knowledge for the next one.

[Blunt Tool]

Re: 40" brick oven on Tasman Peninsula

Hi All,

Christened the oven on the weekend!!

Covered the dome with another 2" of Rockwool, then filled the housing with loose Vermiculite. Lastly added the roof and cleaned up the brickwork. Another (smallish) curing fire on the Friday, and then let her rip on the Saturday!

Ended up having 15 mouths to feed for pizza Saturday night (word spread, things got out of hand ?. ) and I was a bit anxious about pulling it off, so I fired it for about 3 hrs in the morning before pulling out the fire to cook some scrolls for lunch. Relit the fire in the evening for about 2 hrs before she was ready to go. The dome got up to around 500 C, and the hearth over 300 C. Pizzas cooked perfectly!! What a relief!

When all finished we left the coals in but shut the door, and the next morning it was still over 250C in there. Cooked bacon for breakfast, more scrolls for lunch, roast lamb, pork and vegetables for dinner. Threw some baked beans in to simmer overnight but the oven was still 150/160 C and obviously too hot (or not enough liquid with the beans) - they had burnt to a toffee by Monday morning Oven temp was still around 100 - 120C at that point, and when I stuck my head in to have a good look around - no cracks!!

So all in all a very successful weekend. What a relief!!

Just to finish the base now. Originally I had planned to clad that in sandstone rocks but the momentum and motivation have both dried up so we will just paint with a render type finish. I say 'we' because I have outsourced that to the wife!

Thanks everyone for the advice and encouragement along the way!

Andrew

[UtahBeehiver]

Re: 40" brick oven on Tasman Peninsula

Congrats on the completion of the oven and the success of your first party which I am sure we be one of many!

[cobblerdave]

Re: 40" brick oven on Tasman Peninsula

G'day Andrew
Great to hear your enjoying you oven
Regards the beans. It wasn't the temp it was the loss of water. Most folk tend to rely on temperature readings less and less as they get used to their ovens. You cant think of normal recipe cooking times and temps in the same way. Most things can be easily cooked at temperature well over what would normally be used in a domestic oven.
Next time entomb your pot in aluminum foil. Jam the lid on with a piece of foil, then wrap it completely around from a couple of different directions completely around, joints on the bottom. I do rolled oats that way, and it always seems to work
Regards dave

I

[Blunt Tool]

Re: 40" brick oven on Tasman Peninsula

G'day Andrew
Great to hear your enjoying you oven
Regards the beans. It wasn't the temp it was the loss of water. Most folk tend to rely on temperature readings less and less as they get used to their ovens. You cant think of normal recipe cooking times and temps in the same way. Most things can be easily cooked at temperature well over what would normally be used in a domestic oven.
Next time entomb your pot in aluminum foil. Jam the lid on with a piece of foil, then wrap it completely around from a couple of different directions completely around, joints on the bottom. I do rolled oats that way, and it always seems to work
Regards dave

I

Hi Dave,

Thanks for the tip! Will give it a go.
This is the exciting (and tasty) part of the learning curve!

Andrew

[Greenman]

Re: 40" brick oven on Tasman Peninsula

Good to hear that your first big cook went well. I am sure that there will be plenty more good food to come out of your oven. The beans will come right with the right temps and some technique.

[Dario]

Re: 40" brick oven on Tasman Peninsula

Well done Andrew the oven looks very nice, i can't wait to taste food from mine.
You should be proud what you have achieved...
Cheers Dario

[Blunt Tool]

Re: 40" brick oven on Tasman Peninsula

Well done Andrew the oven looks very nice, i can't wait to taste food from mine.
You should be proud what you have achieved...
Cheers Dario

Thanks Dario.

I am actually! Things I will do differently next time, but happy with the way this one is working so far!

[oasiscdm]

Re: 40" brick oven on Tasman Peninsula

Looks great Andrew. You must be chuffed with the result