Another Minneapolis WFO

[Sixto]

Gulf and I have notice that there is a unique smell as the carbon burns off and dome is clearing.

Maybe my thermometer is off? I got up to 700F plus, within 30 degrees across the entire top of the dome, and the soot still has not burned off.... at the very end of the heating-up phase there were a few lighter spots directly above the coals... but who knows... We'll see what 800 degrees looks like tomorrow.


I also tried two new experiments today and they were both resounding successes:

1) I built a smoke diverter using the plywood forms I had made to hold the dome arch while mortaring - yes, the wood charred, but still proved the concept works. (The idea being that since my gallery is so large, the smoke doesn't always go straight-up the flue, depending on what the wind is doing)

To make it, I purchased a black steel elbow and an 8" straight section of 6" diameter flue pipe from the local Builder's supply store, cut an oval shaped hole at the top of the arch forms to insert the pipe snugly, and cut a rectangular slot at the bottom. In my case, the rectangle is 2.75" tall x 12" wide. and screwed two handles on to the plywood. The whole thing goes on and off easily, and fits nicely within the dome arch opening. The bottom rectangular slot provides enough combustion air flow to keep the fire going strong. The two flue pipe sections do a great job of getting the smoke from the top of the arch to the flue, and out of my eyes. I only use the diverter until the wood stops smoking after about 10 minutes, then I set it aside. I will eventually rebuild with a stainless plate.



2) I found a rusty old grate that is fairly light-weight from my fire-pit that is perfect to set the coals on, and move around the dome by picking it up with my turning peel to get an even temperature all around the dome. This is more efficient and more effective than my previous approach of building multiple smaller fires around the dome. It also made the wood burn a little faster, and the floor got warmer all around the grate.

[MarkJerling]

When your construction is still quite wet, 700F may not be hot enough to burn off soot. Once it gets to 900F the soot will be gone.

I do like your flue modification! Might try something like that myself!

Not only will we have the new term "a Sixto landing" but also "a Sixto flue"!!!

[david s]

Be careful with the construction of such a door. Others have built similar and the reduced air intake makes the fuel:air mixture more like the ideal. (search "blast door") This results in the fire starting to roar. We used to do this trick to our fireplace as a kid, holding a large sheet of newspaper across the fireplace mouth allowing a limited airspace at the bottom. The problem is that the fuel content is so hard to control with wood, that the fire roars away forcing a heat rise that's way too fast for the dense oven to cope with. It is the equivalent of firing a kiln at full blast from ambient, something a potter would never do. As the oven is particularly vulnerable when it still contains moisture this practice could end up doing irreparable damage to your oven.
Once your oven is dry the smoke issue should disappear.

[Sixto]

When your construction is still quite wet, 700F may not be hot enough to burn off soot. Once it gets to 900F the soot will be gone.
I do like your flue modification! Might try something like that myself!
Not only will we have the new term "a Sixto landing" but also "a Sixto flue"!!!

kk

Thanks Mark! its fun to try new things, and learn from them whether they work or not. I might try to squeeze in a Pizza or TWO? between the next drying fire and the stucco render on the dome....it all depends on the weather.

[Sixto]

Be careful with the construction of such a door. Others have built similar and the reduced air intake makes the fuel:air mixture more like the ideal. (search "blast door") This results in the fire starting to roar. We used to do this trick to our fireplace as a kid, holding a large sheet of newspaper across the fireplace mouth allowing a limited airspace at the bottom. The problem is that the fuel content is so hard to control with wood, that the fire roars away forcing a heat rise that's way too fast for the dense oven to cope with. It is the equivalent of firing a kiln at full blast from ambient, something a potter would never do. As the oven is particularly vulnerable when it still contains moisture this practice could end up doing irreparable damage to your oven.
Once your oven is dry the smoke issue should disappear.

Thanks David! I totally agree, I still like playing with my fireplace doors too to get the fire roaring when I start it. I will be careful going forward. When I first tried it yesterday, I noticed my fire wasn't big enough to significantly restrict the intake air, which was fine. I will get there eventually, but even then I will only close the "blast dooor" for a short time, keeping a watchful eye on the fire and the temps during that time to ensure things don't get out of hand too fast. I now know how quickly that can happen!

Good timing also, my wife is firing her gas kiln today for only the 5th time since we got it.... still learning a lot about that too.

[UtahBeehiver]

In addition to being our cast expert, David S is also a ceramics and pottery expert as well (gas fired kilns),

[Sixto]

In addition to being our cast expert, David S is also a ceramics and pottery expert as well (gas fired kilns),

Yes, the diversity and depth of knowledge of FB Forum members are just a few of the things that makes it so helpful! Of course, my wife thinks she's the expert with any cooking or fire-related activities in our house.

Dome is starting to clear! Quite a bit hotter fire today... too hot to get my hand inside the dome without welding gloves!



Finally, a photo of my wife in front of her gas kiln - she's firing to 2300F today, so my little 820F Pizza Oven is just a toy to her (but a big deal to me!)

[david s]

Yes, the diversity and depth of knowledge of FB Forum members are just a few of the things that makes it so helpful! Of course, my wife thinks she's the expert with any cooking or fire-related activities in our house.

Dome is starting to clear! Quite a bit hotter fire today... too hot to get my hand inside the dome without welding gloves!

Finally, a photo of my wife in front of her gas kiln - she's firing to 2300F today, so my little 820F Pizza Oven is just a toy to her (but a big deal to me!)

Very nice. You may be interested in my gas fired kiln, which I used my pizza oven moulds to make part of it.

https://community.fornobravo.com/for...608#post446608

[Sixto]

Very nice. You may be interested in my gas fired kiln, which I used my pizza oven moulds to make part of it.

https://community.fornobravo.com/for...608#post446608

Beautiful! - I assume that's all homebrew and perhaps vermi-crete (havent read the thread, but I will) Nice reuse of the existing molds. We went the easy route and bought a ready-made, I am too scared of working with natural gas or propane.

We made lots of progress this weekend. Got the 800F drying fire done on Friday morning, and the dome cleared rather nicely! (making lots of black smoke)

We took the opportunity to make Focaccia and Pizzas Friday eveming (focaccia first - to test oven) The floor was still a little cool, so we pulled the focaccia in after 4 minutes and it was delicious, if a little light in color. Then we made 4 Pizzas and they all turned out great, the last couple were a little hotter, and managing 2 pizzas in the oven was a bit trickier, but we got the golden crust we wanted in about one minute! (maybe too quick?) I think with me working the oven - between 700F to 800F will be the best compromise of speed and workability.



Roasted Garden Tomatoes, Salami and Burrata on the left - Chicken Italian Sausage with Pesto and Sauteed Purple Onions on the right.

[MarkJerling]

Be careful with the construction of such a door. Others have built similar and the reduced air intake makes the fuel:air mixture more like the ideal. (search "blast door") This results in the fire starting to roar. We used to do this trick to our fireplace as a kid, holding a large sheet of newspaper across the fireplace mouth allowing a limited airspace at the bottom. The problem is that the fuel content is so hard to control with wood, that the fire roars away forcing a heat rise that's way too fast for the dense oven to cope with. It is the equivalent of firing a kiln at full blast from ambient, something a potter would never do. As the oven is particularly vulnerable when it still contains moisture this practice could end up doing irreparable damage to your oven.
Once your oven is dry the smoke issue should disappear.

Ah, thanks David! Coincidentally, following a long, wet winter, I started a small fire Saturday to dry the oven out. The dome stayed good and dry through winter, but the floor does get wet because of driven rain getting in on the floor below the door. I can see quite a bit of moisture being driven out through the floor drainage holes, especially with the addition of heat.

[david s]

I recall firing a new electric kiln some years ago and the schedule recommended was to fire it unloaded, but with the kiln furniture in place, up to service temperature with a very conservative temperature rise. I was surprised to see a puddle of water ( around a cupful), pool at one front corner of the kiln at 400C. I would have expected it to happen at much lower temperature. I think what happens is as the water vapour is pushed away from the heating elements, it travels through the insulating fire bricks, hits the cooler stainless outer sheeting, condenses back to water and falls to the bottom, with some steam pressure forcing it out at the base.
Regarding rain entry, our oven gets a bit wet from driving rain in our wet season from tropical storms. On one occasion the oven was wet even though we hadn’t had any driving rain, because in really high humidity the refractory and insulation will pick up moisture from the atmosphere alone. The outside of the oven was hot to the touch after an hour of firing which is an indication of moist insulation. Also I once opened the oven door after wet weather and was surprised to see mould growing on the inside of the oven. I now prefer to leave the door off in really wet weather to allow air to circulate. A couple of slow fires always restores the oven to normal working condition.

[Sixto]

Saturday morning, my buddy Nick and I started adding the stucco/render to the exterior of the dome, got a couple of coats on, then decided to call it quits till we had enough energy to finish. (Plastic cover is on) so far, so good! Also a photo of the dome when it finally cleared last Friday at over 800F.

[david s]

You will probably notice the oven continuing to improve in performance (shorter time to clear and longer time retaining heat) for around another dozen firings or so. You may be interested in cooking other foods. In my oven I fire until it starts to clear at the crown, which takes exactly one hour of flame, if the oven is in normal condition, it will then be around 270C. I let the flame die, push the coals aside, place the roast and seal the door. A good guide (from Weber) is one minute per mm of the thickness of the roast. So for a 120mm thick roast you'd give it two hours.

[Sixto]

You will probably notice the oven continuing to improve in performance (shorter time to clear and longer time retaining heat) for around another dozen firings or so. You may be interested in cooking other foods. In my oven I fire until it starts to clear at the crown, which takes exactly one hour of flame, if the oven is in normal condition, it will then be around 270C. I let the flame die, push the coals aside, place the roast and seal the door. A good guide (from Weber) is one minute per mm of the thickness of the roast. So for a 120mm thick roast you'd give it two hours.

Thanks David, I will be trying lots of different foods, and will continue to report on my progress, both here, and on the Cooking threads. A dozen firings is within sight, but then it will also be winter here from November through March or April...I'm not sure how much I will use it during that period, since I don't have a roof over the dome...and my little tent will not hold up to a significant snow... We'll have to see how much cold and snow I can stand to work-in for the rewards promised by the oven.

By the way, the crack on my dome arch is camouflaged behind a layer of black soot. Only I can see it now, and I don't even look for it anymore... Especially when I'm too busy cooking!

I finished the plaster/render on the dome today (doesn't look any different than the photo above, just added some layers). I will wrap it with plastic tonight for a week before I try firing up the oven again. In the meantime I'll be perfecting my Pizza Dough recipe in my gas oven...not as hot, but good enough to get a feel for what I like.

I know it's early, but I'm quite happy with my Pompeii Oven so far.

[UtahBeehiver]

Look at a thread by Karangi Dude out of Aussie land. He does all kinds of WFO foods and use to teach WFO cooking to mates in Queensland or Victoria.