pompeii oven construction began today

[Alan]

Perhaps your wood consumption situation will improve when you've added additional insulation. The 4.5" thick walls will take longer to heat up than thinner walls but with enough insulation they should stall hot longer as well. If the outside of your present insluation feels significantly hot, then you're losing heat and need more insulation.

The other area of loss is of course the opening. But the main source of draft in along the floor is the air needed to feed the fire itself, and there should be a net gain.

[paulages]

i agree with your "can" analogy. i build the biggest fire i can as quickly as i can get it big, without ablsolutely spilling flames straight out the front. i burn it like this until everything is white hot, then move the fire to the side and cook.

madrone is working very well for me for cooking. all of the softwood i have pops too much, even though it is very well seasoned, so i use it for firestarting. madrone is supposed to burn really hot. seems like we have a similar system.

[Robert Musa]

with respect to the fuel issue, for what its worth, i too have the perception that i'm using an enormous amount of fuel. last year during the "pizza oven season" we went thru well over a cord of almond using the oven 2 and 3 times per week. and... my oven is really well insulated. 900 degrees inside and cool to just warm to the touch on the outside.

i'm tending towards the following conclusions:

1. heating the oven to the desired temp is like filling a can with a small hole in the bottom. that is; its better to get it to a state of "full" by pouring in as much as heat as fast as you can as opposed to slowly feeding the oven heat. i think i used too much fuel last year because i built (and then fed) medium sized fires while wating for the dome to heat up, when instead i should have built the type of fire that melts your eyeballs right out of their sockets as you approach the dome. in fact, my kids are much better fire builders because in their opinion no fire could possibly be big enough.

2. the type of wood really matters for taste. i use my "trash wood" like pine and yard trimmings to get the fire started and then switch to the almond for taste.

[paulages]

overkill is relative to price. if a refractory cement or inulation is rated 2-3 times higher than an oven will ever heat up to, it will still work fine at lower temperatures, and may be more cost effective than buying and mixing your own materials.

[Marcel]

To Jengineer on AbleRefractory insulation; no Group buy

Dear "JE"

You wrote: "Are you looking to set up a group buy?

(M) Nope.

(JE) From the looks of their web pages I would think that these folks are more apt to deal in large bulk quantities.

(M) I tend to agree with your guess.

(JE) Say your local electic power producer that uses coal/gas to fire the furnaces. In the same breath they also point to insulating dentist furnaces.

(JE) From the pdf product sheets their mortors would be overkill for the oven however their blankets could reduce the size of the insulating.

(M) That's waht I hoped to hear from them, possibly accompanied by Tech. Specs. concerning thicknesses of blankets, and area.

(JE) A possible substitute for the Vermin-Cellulite or Pearl-Lite?

(M) You got it. Other postings, such as Paul's bemoaned the amount of fuel he is using. He, for one, is considering adding more insulation on the dome. Others have responded here and suggested options other than Vermiculite &/or pearlite. I want to plan ahead and contributors like Paul et al have already saved me countless hours and dollars by reading of his or her experience.

(JE) You might want to follow this up with one of their sales reps.

(M) Let's see what they write back. We're speaking of such a small amount that if it isn't available locally, I'll date Pearl or Verma.

je - lurking in so-cal

(M) I used to live near Griffith Park. Thanks for your help.

(M) Marcel

[jengineer]

oh Boy

Are you looking to set up a group buy? From the looks of their web pages I would think that these folks are more apt to deal in large bulk quantities. Say your local electic power producer that uses coal/gas to fire the furnaces. In the same breath they also point to insulating dentist furnaces.

From the pdf product sheets their mortors would be overkill for the oven however their blankets could reduce the size of the insulating. A possible substitute for the Vermin-Cellulite or Pearl-Lite?

You might want to follow this up with one of their sales reps.


je - lurking in so-cal

[Marcel]

A letter to AbleRefractory insulation in Texas

To: AbleRefractory.com

I am in the process of building a masonry wood burning outdoor oven. The design is essentially like that of an igloo. The dome structure is made of refractory fire brick covered with refractory mortar.

The next very important stage is to prevent the heat from the inside of the "igloo" from escaping through the bricks and mortar.

I see that your Co. produces a very wide range of products to meet the needs of vastly different applications.My question to you is given the novice description of the 42" diameter oven, what product(s) would you advise as best suited to keep the heat inside the oven?

_____________, ____________,

================================================== ================================

I live in west central Oregon, not too far from Eugene. What are the closest retail outlets in that area, if any? ______

================================================== ================================

Thanks for your time and trouble,

Marcel Demiranda
marceld@efn.org

P.S. I am posting this inquiry on the Forno Bravo oven forum.

[paulages]

i can definitely believe there is still moisture in the hearth. it hasn't been ridiculously hot here in the NW, and the slab inside my barn (from posting #1, when i poured the foundation) is STILL not cured enough to move in with the acid etch staining coming next. granted, the hearth was poured outside, but it was also poured much later.

i hope you're right, james. right now i feel like i'm gonna go through my winter's firewood supply in no time...

[james]

Paul,

My guess is that you are still driving moisture out of the bricks, mortar and hearth concrete. Give it a little time, and it will get better (hotter and faster) with each subsequent firing.

James

[Alan]

Paul, should you decide to leave a thermocouple on the outside or shove one in between the rigid insulation and the vermiculite before closing up the roof, remember that with the vermiculite added the outside of the chamber should be hotter than it is now. There should be less total heat loss, but a higher temperature on the outside of the chamber. Think of it as a bunch of resistors in series: dome walls - rigid insulation - vermiculite - outer walls - air interface, with the oven temp and air temps as "voltages" at the two ends. Adding more resistance bewteen a given spot and the outside will always bring that spot's temperature closer to the oven chamber temperature. Real heat transfer's not quite the same since the transfer to the outside air is horribly complicated, but the analogy still works in terms of when to expect things to be hotter or colder.

[pam]

chimney

i am anxious to see how you tackle the chimney ...

i found a place in dallas where i can order terra cotta chimney sections for about $13 each ... they're 8" a-oval and about 2' long.

[paulages]

the insulation seems to work fairly well, though i ended up going thinner with it than i'd liked, because i didn't wrap the oven in chickenwire first. consequently, i couldn't pack it on as thickly as i'd liked on the sides without it sliding off. the top has about 2-3 inches or more, but the sides are probably more like 1 1/2" -2" max. when the oven has been heated for a while (2 hours or more) the walls heat up to about 150deg. F, when the interior walls are 700-900deg. F. this is about a 100deg. drop from before insulating, but still higher than i'd like. what do the vermiculite insulated walls heat up to, anyone? since this stuff was free, i'll probably add another couple inches before all is said and done.

also, i am having problems reaching the temperatures i want. mostly in the floor, but even in the walls, i have to have a pretty damn big fire going to keep proper temperatures. having a 42" oven is probably part of it, but i also feel like i'm losing a lot of heat into the hearth. i definitely am burning more wood than described by some people on here.

[paulages]

it's alive!!!

okay, i'm having fun making pizza every night, but i guess i should move forward and get to work on the vent, walls, roof, and all of that other stuff i have to do before the rain comes. here's a nice photo of my oven in action:

[paulages]

insulation time...

here's a photo showing about how thick i spread the insulation, and another showing it fully covered. i ended up going a bit thicker on top, as it seems to heat up considerably more there, and i'll most likely fill the sides with vermiculite once the exterior walls go up anyway.





i'll post before and after specs after it dries and i've cured the insulation properly.

[paulages]

since the foamboard method is the only one i've tried, i can't say whether it's best or not, but it sure worked well.
maybe it would take you, jim, robert, or someone else who has tried other methods, to try it and compare.