36" in Seattle

[Tscarborough]

Re: 36" in Seattle

No, you are correct, Kebwi. The important factors for good draw are Square inches cross section of flue, smoothness of transitions, and height of stack.

There are formulas for fireplaces, but I do not know of any for ovens. From what I see of the ovens posted here, the main problem is the size or lack of a smoke chamber. If the inner arch and outer arch are the same height, and the distance between them is too small to allow an adequate sized flue, then the stack height has to be increased. Conversely, If the entrance to the flue is above the height of the inner and outer arches, then the stack height can be decreased, although the flue size should not be. A smoke chamber is the area above the level of the arch(es) up to the entrance to the flue. For fireplaces, it is generally as tall as it is wide, although that is not practical for the design of the Pompeii oven.

What I have found for problem fireplaces that smoke is that standard fire lighting practices have to be altered (and for ovens, I am guessing that this is the optimal way anyway).

A small, hot, smokeless fire should be built to pre-heat the flue. Fat-lighter or firestarter logs work well for this. Once the flue is warmed up, the fire should be built up gradually instead of creating a pyre and lighting it off all at once.

Personally, I do not ever expect to have smoke come out of my outer arch, other than a stray puff from a breeze.

[kebwi]

Re: 36" in Seattle

While I've got your attention Tscar, do you mind me picking your knowledge brain a bit?

I inquired about the necessity of bolt/washer "T-locks" to hold the hardi to the vermicrete and you had been of the opinion that it would be unnecessary, that the hardi would adhere to the vermicrete. I'm not accusing, honestly, I just want to know how to do things correctly. As you have noticed, I used locks anyway, but for a few small sections of hardi I didn't bother, and after curing, those sections of hardi fell right off (see the photo of my eighth curing fire for an example). I had sponge-damped the inner face before filling the vermicrete, but it didn't stick anyway.

Do you have any thoughts on what I may have done wrong...and more critically, can you alleviate my fear that the SBC will suffer from a similar problem on the outer surface?...or what I should do to make sure it works properly unlike the vermicrete?

What do you think of this? Why didn't the vermicrete stick to the hardi? I'm just not sure what I did wrong and I don't want to make the same mistake with the SBC.

Thanks for any advice.

Cheers!

[Tscarborough]

Re: 36" in Seattle

You didn't do anything wrong, until the SBC is applied it is as fragile as the weakest part, i.e. the vermi-crete. Vermi-crete/perl-crete have adequate compressive strength, but almost zero shear strength.

Just prop those pieces back in and apply the SBC, no worries.

[kebwi]

Re: 36" in Seattle

Yay, my 600th post. Somehow, I missed #500 as it flew by.

Here's the tenth curing fire, well into the low 800s at the top of the dome. My makeshift door is evolving; I added a 1000F thermometer, obviously intended for the final door. I had the idea of throwing some frozen bread dough (just crap from the store) on the hearth after I killed the fires and let the coals smolder for a while, but alas, the new thermometer barely broke 220F, so I didn't do the dough.

I'm still learning how to fire this thing (and still driving out some moisture I'm sure). I'm not running long fires, I admit it, maybe 30-45 minutes tops, and then I'm intentionally spreading the fires out because I don't want to stress the curing process (although I think I'm basically done now, two 800F fires, going for 900 next time), but nevertheless, I am hitting those temperatures, so I'm a little confused why I lose so much heat so rapidly (almost instantly) when I kill the fire. Where did the heat go? I would think that it isn't "soaking through the bricks" because I would expect the bricks to not reach 800 in the first place unless they were pretty darn hot all the way through...but I realize that everyone's testimonies suggest they fire for two solid hours when cooking, so I'm sure I just need to get into full gear and start loading wood in by the wheel-barrow full. I'm just a tad surprised at the rapidity with which it loses heat at the 30-45 minute mark.

Continuing this thought, I am not sure how to fire for cooking if I can't simply assume that meeting the target temperature is the proper indicator. After the dome hits 800-900 degrees, what else do I do? Just run the clock out for 90-120 minutes and then hope it's ready? That seems a little arbitrary. I guess there's this business about the dome going white, then spreading the fire so the white spreads down the sides. I haven't seen anything remotely like that (my oven is the blackiest blackestest shade of blacky black I've ever seen!).

Anyway, all's well, I expect things to work properly within a week or so. My plan is for pizza next weekend and bread the next day!

Final note to Seattlites: The Seattle Restaurant Store in Shoreline ROCKS! Thermometers, peels, pans, cutters, scales, brushes/rakes, absolutely the works, and they're open Saturdays.

Cheers!

[kebwi]

Re: 36" in Seattle

Made my first pizzas tonight! Here's the fire, the dome went over 1000 (my thermometer stops registering above 1000 so I can't specify measurements after that point). I still have exposed InsWool HP on top of the dome, about four to five inches. It went up to 140 and produced hoards of steam. However, where I have already poured vermicrete over the InsWool there was practically no rise in temperature, so I expect good results after I pour the third and last terrace of the enclosure. I think it was a good idea to drive the moisture out before enclosing the vermicrete anyway.

Despite the high temperatures, the whitening only came part way down the dome, as you can see in the photos. More discussion of this and other aspects of the actual cooking in the next post.

Pizza pics to follow...

[kebwi]

Re: 36" in Seattle

Inaugural pizzas.

These were made from approximately a half-batch of the FB napoletana recipe, although we rounded a little up on the yeast. The FB pizza book includes both volume and weight measurements and they don't seem to be in agreement and the volume measurement seems very very low (in yeast) relative to other pizza recipes (and about half the weight measurement in the same book!).

Anyway, Caputo 00 pizza flour, San Marzanos, mozzarella, fresh basil. A second pizza with the same and also including black olives and some red onion.

The cornicone didn't puff up at all, not the slightest bit. In addition, I lost a lot of heat. As you can see in the previous post and in the cooking photo in this post, the whitening of the dome never came down the sides. By the time I was cooking, the dome was around 500-600 and the floor on the pizza side was around 200-300. Took upwards of ten minutes to cook each pizza.

Admittedly, I hadn't done a very good job of keeping the fire going. I left it for a long time to go inside and make the pizzas, duh!. When I came back out, there was a very nice bed of coals, but no actual flame. The photos don't show it, but for the second pizza, I added some wood and "bellowed" it up to a good little fire, but it was too late, the oven had cooled too much and the pizza was already in the oven. It obviously doesn't work that way.

Live and learn.

My only real concern is the lack of "puff". Would that have worked better if I had maintained better temps? What actual temps do I want to see on the dome and the floor via IR thermometer? Should both be 900 during cooking?

Oh right, and my second pizza tore on the oven floor, thus becoming a donut pizza. Sigh.

[david s]

Re: 36" in Seattle

Kebwi,
If you still have a black rim around the bottom then it means you still have moisture in your oven. You will probably find it will all go white the next time you fire. You will also find that your oven will get up to temp faster and retain heat better the more you use it

[david s]

Re: 36" in Seattle

Forgot to add that you will also find the ovens fuel consumption will also drop as it becomes drier.

[kebwi]

Re: 36" in Seattle

Yeah, that makes a lot of sense. Water has a tremendous heat capacity, so it will kill the efficiency of any oven. I am a little concerned about water in my current design. The goal is to fully waterproof the exterior with a shell of acrylic fortified SBC, perhaps even coated with additional concrete waterproofing on top of that. The reasons are two fold. One: I live in a wet area (Seattle), so water will be an aggressive problem, and two, my design will have dirt and plants on top of it and I don't want the moisture seeping through the exterior facade (I intend to put plastic under the dirt, but still...)

Problem is, I envision water constantly seeping into the bottom of the oven across the hearth. In fact, I hope the InsBlock doesn't slowly rot out from under the oven. Whenever water seeps in under the oven, it will only have one way to go: up. As the oven is heated, the water will wick (and boil and steam) its way up through the InsWool HP insulation to the top of the dome, where it will be effectively trapped under the SBC exterior. I'm not sure what the long term implications of that are.

[bbell]

Re: 36" in Seattle

Keith, congrats on the first pizzas! I too think the oven will need a couple of more rounds to get rid of the moisture. Also, I found it best to keep a healthy fire going while pizza baking is in full swing. See pic.

Did you ever find Pacific Food Importers (Big John's PFI)?

[kebwi]

Re: 36" in Seattle

Re: Big John's Pacific Food Importers:

I intend to head down that way at some point. They have bulk and large volume Caputo flour, but they're so far away that the savings are only realizable if I buy a pretty significant amount. I'm not sure of the rate I'll go through it relative to its shelf-life. Bottom line, it's about $2/lb at Metropolitan Market and $1/lb at BFI, and it costs me about $2 and half a Saturday to drive there and back. If I buy 20lbs, that's $18 saved and much of a weekend shot. I dunno, maybe it's worth it.

Anyway.........

[vintagemx0]

Re: 36" in Seattle

I have to agree that you probably still have some moisture in the brick. I don't know how long your fire is, but I find I need to run mine hard for 1-1/2 hours for the bricks to saturate with heat. It used to take about 2 hours, but is easier to light and takes less time now. If you only burn it for about 50 or 60 minutes, I would think that a tremendous amount of heat is travelling through the bricks to their cooler side. There's a lot of mass to thoroughly heat there.

I was having the same performance "issues" you were, but you'll quickly learn what your particular oven needs. After my last pizza cook, I was amazed at the heat retention with the door installed. We had usable heat degrading only to 225 degrees after 2 days! I don't think it would have been very good with only 50 or 60 minutes though.

At this stage in your curing, try a good hard 2 hour burn, then cook your pizzas with a small log burning on the coals off to the side. I think the proper temperatures are a variable you need to consider in the quality of your dough too.

Congratulations! It's good to see your ready for summer.

Ken

[Tscarborough]

Re: 36" in Seattle

I am a believer in a small fire to start then the big one. It seems to me that if you just start with a Big Scary Fire, then you are losing a lot of BTU's up the stack. There is a limit to the rate of heat absorption of the masonry mass, and I don't think it is linear. That is, the hotter it is, the faster it will absorb heat up to the point where it is heat-saturated.

I could be and am probably wrong, but that is my theory.

[kebwi]

Re: 36" in Seattle

I see, so a long moderate fire as opposed to an instantaneous bonfire. I suppose I can see the argument for that. I don't know if it's within the purview of my personality though.

[Tscarborough]

Re: 36" in Seattle

Well, at some point you have to have a big fire to hit those temps. It just seems to me to be moderately more efficient to ramp it up to that level.