Heat break at arch

[david s]

sounds like advertising spam to me.

[Lburou]

I made heat brakes, but it is not necessary at all. I posted temperatures a couple years ago when I finished, but didn't bookmark the data. There is significant temperature difference at the break between the dome and the arch of the flu...my memory is in the ballpark of 135 F difference. I made a heat brake on the threshold as well to protect the granite from spalling. It works as designed. But, the heat brakes are totally optional and probably a lot of work for a small gain. The real gain, it seems to me, is in the insulation of the dome. I put pictures of my heat brakes and some of the temperatures Les asked for in my album descriptions I think...but don't know if you can see them since the recent software "change". HTH :-)

[cobblerdave]

G'day
The links to your 1 meter oven and heat but brakes appears to be broken. It would probably need admin to reconnect. Just thought you might need to know
Regards dave

[Lburou]

Here is a picture of my heat brake at the oven arch, the isolation of landing arch and the flue riser, and the heat brake for the granite on the landing. HTH

Admin knows the albums are not working yet. :-)

[mefornaio]

Don't know why the recent posts, look like this thread has been dead for a while? I thought Id ad my 2 cents.

The gap shown in the photo between the granite and the dome should have been sufficient for the heat expansion not to effect the granite slab. After a few uses that area would have filled with ash as do floor joints.

Concerns about the granite cracking from expansion of heat (Im assuming the concern was oven expanding and pushing on the granite slab?) The whole oven and base slab are heating up as a unit, everything is expanding slightly at such a gradual rate the granite slab unless in direct contact with flame isnt going to be effected.

It takes a lot of localized heat (direct flame from blow torch is what we have used) to spall a granite face or cut edge. Temps even at firing wouldn't get close to being a concern unless you had burning fuel (wood) in the oven opening.

As to heat loss form the entrance and decorative arch this is not even worth a concern for these ovens. The usable bake time to thermal storage relationship in these pizza ovens is low purposely by design. In contrast to a pizza oven a bread oven has much more thermal storage because of thicker walls that equates to more storage. EVEN THEN the impact on thermal loss,draw or what ever term is used as other have noted has an insignificant impact on performance.

[Lburou]

....The gap shown in the photo between the granite and the dome should have been sufficient for the heat expansion not to effect the granite slab. After a few uses that area would have filled with ash as do floor joints.

Yes. Except the floor is contiguous to the heat brake at the granite, four or five inches from the inner arch to the oven. Yes, the heat brake fills with ash by design. Fornobravo threads are replete with reports of spalling of granite in similar installations. They are reliable reports from builders who have real experience. Flash temperatures to more than 1000 F will cause spalling over the working lifetime of the oven without this heat brake. I heat the oven quickly, to a high temp, storing the heat you mentioned to slow cook four days after pizza. It is always worthwhile for accomplished builders, (i.e., Greenman, David s, Cobblerdave, & NCman), to share their experience when a 'resurrected' thread appears in a search, providing corporate memory for the new user. :-)

[mefornaio]

Flash temperatures to more than 1000 F will cause spalling over the working lifetime of the oven without this heat brake.

I know attitudes can flair up quickly on forms like these. My comments are made matter of factly NOT with attitude.
That thermal break will do NOTHING to prevent spalling. Spalling is a surface condition not remediated by expansion joints. The granites location in relation to the heat source in this application and Im assuming all the others you reference is/was the cause. I'm sure the other "experienced builders" will not hesitate to agree.

Not sure how long you have been operation a brick oven but quick firing is counter productive to maximum heat retention, it also created localized hot spots that depending on what you are slow cooking can not be helpful.
You would be much better to do a long regulated burn and a soak cycle to get maximum even absorption. In this way you allow the heat to reach all the way to the insulation layer. Try it im sure you will be happy with results.

[Lburou]

No attitude intended mefornaio. :-)

[mefornaio]

No prob Lee I didn't mean to imply you had one I just wanted to make sure my reply wasn't coming across with one.