Greetings from NY

[delay!fox]

Hey Folks...

Looking for some helpful tips, Very Green. I am in the midst of building the "Pompeii Oven" and am at the point of building the hearth. I have a couple of questions which I hope can be answered by someone with knowledge on the subject matter of wood fired ovens and or the Pompeii Oven in particular.

1. Thermal Mass: I was in Greece recently and met an old school wood fired oven builder. This Gent used a considerable amount of Sand and Pumice stone in his hearth as opposed to the materials that are used in the Pompeii Oven instructions. The Oven I saw retained heat for the better part of the day and evening and well into the night, which was impressive. FYI this was not a "pizza oven" but a round wood fired oven which was used for bread and roasts.

Does anyone have any comment on how long the Pompeii Oven retains cooking heat (as it is designed)? Is there anyway to increase that time by altering the hearth construction to include sand or other materials.

2. Fire Brick Dome: I've seen a few pictures where shims are used to create the dome. Can anyone tell me if these can be purchased or if they need to be made at what specifications.

3. Fire Brick: This is a killer for me. I have no idea how to find or judge quality Fire Brick. Any suggestions.

4. Fire Brick Cutting: The thought of cutting aprox 150 or more Firebricks for a 42" Oven is something I'm not looking forward to. Any suggestions on how to accomplish this task without using a saw would be helpful.

5. Any other comments or helpful hints on areas where I should be careful would also be appreciated.

Thanks to all who respond. Again I am new at this appreciate all of your assistance.

[egalecki]

Re: Greetings from NY

Ok, let's take it from the top (all advice in my opinion, of course, others may differ, as always )

the guy in Greece may have been old-school, but how much wood did it take to heat that baby up? And how long? I can get mine to pizza temps in less than 2 hours (still drying out). It stays hot enough to bake bread the next day (if I use my insulated door) and other things, as it loses heat gradually. I think it has more to do with insulation and less to do with extra thermal mass. If you use half bricks, you should have enough mass.

Shims- you can buy packs of shims at the builder's supply, or you can make them. Some people calculate the angle carefully and shim accordingly, some people just go with what looks right. I went with what looked right. I also used a string to measure the distance from center to the face of the bricks in each round to make sure I was not "out of round". You can also use bits of cut off brick, pebbles and sticks. Whatever gets you the angle you need.

You want low to medium duty fire brick. I think a regular size medium duty weighs about 9 pounds. Anything significantly heavier is much harder to cut and not worth it. You really only need the good ones for the floor- and you judge that by what they look like. Are they straight and square? Can you lay them up side by side and not have a lot of gaps and bulges? If so, it's all good.

I only cut enough brick at a time for each round. I bought a little wet circular saw at Lowe's- about 80$ and it paid for itself many times over, even buying new blades and cutting only halfway thru each brick. I used a hammer and wedge thing to split them the rest of the way. Other people have rented saws, some bought really nice ones. I would recommend not cutting too many at once no matter what, so you don't end up with 50 extra half bricks when you need to switch to the 1/3 size near the end... but I'd use a saw if possible, because it's really hard to do it without one. You can use an angle grinder (I got one of those too, worked great) but it's even louder and much, much dustier. Whatever you choose, use ear and eye and nose protection. No kidding.

Insulate underneath the oven, either with the vermiculite concrete or the board (I used both) and the outside (2 layers of blanket and 4" of vermiculite concrete here). You won't be sorry.

[nissanneill]

Re: Greetings from NY

Hi Delay!fox, and welcome aboard.
Elizabeth has cornered the question market and I agree with most of what she says.The "Gent used a considerable amount of Sand and Pumice stone in his hearth as opposed to the materials that are used in the Pompeii Oven instructions" quite probably used pummice because:
1. it was available, cheap or free for the picking up in certain locations. and
2. it is very light, filled with insulative air pockets and is an excellent insulator.
You could probably use a similar material that we have out here down under called scoria.
The sand would add to the thermal mass more than it would insulate.
You need to make the right decisions if you want to cook pizzas only or mixed cooking, eg, breads, roasts etc. You can cook anything you like. The retained heat is determined on how much heat you have in your oven and as Elizabeth said, how well the oven was built and the type and amount of insulation. Skimp on this and your oven will only be hot with a fire or coals in it. Insulate right and thoroughly with a good door and your heat is retained for 24 hours or longer.
You might like to check out my build as all of your concerns are covered with explanations and pictures for a 40" Pompeii at:

http://www.fornobravo.com/forum/f8/n...-1-a-2005.html.

I didn't use shims or wedges but I did use a sticky cheap mortar which held the brick exceptionally well and it stayed where you put it. My dome and hearth were built in 2 days and what's more it was raining so it was under a tarp!
There is a lot of information on fire bricks but I am not convinced that they are necessarily the only option if other proven bricks can be used.
If you want to go down that path, then I would stick to low to medium fire as you will experience huge problems cutting the heavy high fire bricks, they are like cutting a solid block of steel an that is with a commercial 14" diamond brick saw.
Don't panic at this stage as everything that needs to be done is just one simple step after another, There is a huge amount of information here and plenty of advice and help when needed.
Do your homework, your research, make some decisions, gather your materials and go for it. It is well worth the effort, believe me, mine is only a year old, I don't use it as much as I should but am building a new patio area around the oven which will then become the centre for entertaining the family and friends.
You will need some equipment and tools to complete it but the tools are basic and cheap, but buy a reasonable saw which will more than pay for itself and you will have it for many other types of job if you buy right. Get a few quotes on getting someone in to do it for you and that will put you off. My whole oven cost $1200 with everything, cast doors, laser digital thermometer, lights and all materials. Others on this forum have built for a lot less and other much much more.

Good luck with your decissions

Neill

[james]

Re: Greetings from NY

Great advice all.

I think the "sand, ash, pumice, crushed glass" insulators were all used because they were better than nothing, and somewhere between free and cheap.

Insulation is one place you should not skimp. It isn't expensive and you cannot even image how much it works. After a little time with your oven you will know what we mean. Fast heat up, less wood burned, longer roasting periods, easier to keep at high heat, etc. Day and night.

On the firebricks, you can safely buy whatever line of firebricks your local masonry supply store carries for fireplaces. That will do it.

More importantly -- enjoy your project! It will be great.
James

[delay!fox]

Re: Greetings from NY

Hi Elizabeth,

Thanks for taking the time. I have to tell you this oven I saw took 2 small stacks of Olive Tree Branches to get to the temp needed to cook a whole 35 lb lamb on the spit in just over 2 Hrs... They stuck the whole spit in the oven ((with the just part of the handle sticking out and the oven opening enclosed with some ceramic tiles as best they could. For someone who has a rotisserie and has cooked lamb on the spit I can tell you that it took me around 6 hours to cook a lamb 1/2 that size. The only reason I bring this up is because this is what led me to the "pompeii" journey. Never tasted something so tender. To conclude, some of you are right, the materials of Sand and Pummice are plentiful in Europe as well as cheap however I wonder if the "old school masters" know a thing or two through experience.

I would however like to stress the importance of using this oven for both Pizza but equally as important for cooking roasts, bread, etc. Is the Pompeii Oven design appropriate for this use? If not, I am at a point where I can make adjustments.

Thanks again all, you have been great...
---Paul

[Frances]

Re: Greetings from NY

I would however like to stress the importance of using this oven for both Pizza but equally as important for cooking roasts, bread, etc. Is the Pompeii Oven design appropriate for this use? If not, I am at a point where I can make adjustments.

Paul, it is. It really really really is. These ovens are incredible, and baking or roasting in them is a joy! Just go for the higher dome version, which is better for bread and such.

I think with this forum and so many oven builders contributing to it, the plans are continually being improved and adapted to individial circumstancs. As for modern insulation, there are builders who have used other insulations and regretted it... but the plans did originally come from the old Pompei ovens - you can't get much more "old school masters" than that!

[delay!fox]

Re: Greetings from NY

Ok... sold... we follow the "Pompeii Plans" as is.

Please allow me to pick your brains a bit more...

1. The instructions on the Block Stand call for 9 pieces of 40 Inch Rebar to be placed at every other core, filled with concrete. In measuring the height of my 4 rows of Blocks I'm at aprox 31 Inches. Can someone solve this riddle for me? Should the Rebar extend over the Block Stand and ultimetly be attached to the Hearth or should by Rebar be at 31 Inches?

2. On the matter of "Framing the Hearth" (page 22 of the Pompeii Plans), there is a notation that addresses how to increase the Thermal Mass in the floor to allow for longer cooking times at elevated temperatures by using an "isolated hearth...(ie. a ) a ring of refractory pour dome, or b) and island of firebricks is set under the cooking floor or c) sink your island into the insulating layer. Can anyone give me a little feedback as to what option if any you all used?

[james]

Re: Greetings from NY

The more we have all learned and the more ovens (Pompeii Ovens and FB ovens) we have installed, the more I think that the standard oven is right for a vast majority of owners. I've done both and watched the results. Unless you want to bake commercial quantities of bread, I don't think the extra mass under the oven is necessary -- and it can even make pizza baking and maintaining heat on the cooking floor a little more challenging.

My two cents.
James

[DrakeRemoray]

Re: Greetings from NY

Hey Delay,

on number 2) that isolated (or island) hearth was an idea before many here had built ovens with no additional mass on the hearth. My oven has bricks laid directly on perlcrete, but with about one inch of additional mass on the dome. It takes about 1 1/2 hours to come up to full pizza heat, If I make pizzas for a few hours, which I usually do, then it will be at 350-450 24 hours later and 250-325 in 36 hours. It will cook waaaay more food than you can eat. In one firing, I have cooked 14 pizzas, 2 large foccia sheet pans, 25 lbs or bread and a pork roast on the first day, then chicken and potatoes, short ribs, and a pot of beans on day two...So I think there is plenty of mass, but I do have a tad extra in the dome as I mentioned...I usually am waiting for it to cool off so I can start baking bread at 550 or so...

Can't help on number 1)
Drake

[delay!fox]

Re: Greetings from NY

Hey John,

Quick question. I'm trying to figure out if I have enough room for a 42" oven based on my corner instalation with a hearth of 62" sq. I guess it all depends on whether I build an Igloo or Wall enclosure. Regardless, do you have any idea what the size is (Length x Width x Height) of an average Light to Medium Duty Firebrick? I'll add up all the layers and see what can fit. Thanks.

[brokencookie]

Re: Greetings from NY

Here is a calculation straight from the horse's mouth - James ( not to be confused with the horses other end )

"For oven width, take the exterior width of your oven (oven floor, plus oven wall width), then add 10" for your insulation (1" insulfrax and 4" vermiculite), then add the thickness of your enclosure walls (1/2" for an Igloo, 2" for a metal stud wall, 4" for a concrete block split, etc.)"

"Standard" fire bricks come in a wide variety of sizes. I believe the most common size in the US is 9 x 4 x 2.5 inches

Check with your local supplier for exact dimensions.

[delay!fox]

Re: Greetings from NY

I need a bit of help folks.... James? Anyone?*Vermiculite Related Question *

I have just completed the Hearth in two stages. First stage was the 3.5" Rebar Reinforced Concrete which cured for a week. Then I added the 4" Vermiculite Slab. I am a little concerned however in respect to the Vermiculte slab and need someones advise.

I laid the Vermiculite Slab on a Saturday Morning and it is now Sunday Evening and the Slab still feels "Damp and Moist" unlike the Concrete Slab which had dryed out by the next morning. Further, in looking at the photo's from the Pompeii Plans, the Vermicultie was gray and lumpy. My Slab is light brown (((a sand color ))) and has a smoother texture.

Just to make sure I give you all the information you need, the plans called for 5 Parts Vermiculate and 1 Part Portland Cement. My interpertation was 5 Buckets of Vermiculate to 1 Bucket of Portland Cement. A

Also the plans called for 2 x 4 cu ft Bags of Vermiculate and one bag of 94 lb. of Portland. I ended up needing 3.5 Bags of Vermiculate and 1.5 Bags of Portland for a 62" x 62" x 4" Slab. Not sure if these details are important but I thought I would share.

Can someone put my mind at ease??? The last thing I want is to take the forms off only to discover that the Vermiculate Slab is not Strong enough to support my oven.

[RTflorida]

Re: Greetings from NY

Your mix sounds fine, I too used a bucket to measure (the same 5-1 ratio).

As for the color, not sure of variations.....portland is usually grey, vermiculite a sandy brown (at least mine was) so I would think any hue between light grey and light brown would be possible.

the consistency - it will feel damp and moist for several days and the glossy/slick look will dissipate along with the moisture - looking even more crumbly as it drys out. From your pics, things look fine to me (just a little more brown in color than mine).

I have two questions - 1) Did you use agricultural grade vermiculite? That is the one you want. There is a type of vermiculite that is treated with silicone to be used as wall insulation...not good, as the silicone does not allow adhesion with the portland cement. 2) What size vermiculite - fine, medium, or course? Naturally, this would effect the the appearance; I don't think it affects the strength or insulating value. In my shopping I found medium to be the most readily available (and what I used).

One last point, don't be in a rush to take off the forms. Give the vermicrete at least a week to cure before proceeding and you should be good to go.

RT

[delay!fox]

Re: Greetings from NY

OK.... here it is...

The Bag of Vermiculite has the following information, and for the life of my I don't understand why I didn't pay closer attention to this sooner.

A-TOPS Vermiculite Masonary Insulation
Water Repelant For Block & Cavity Walls

No mention of any of the other information you requested...

From your last posting I would say i am screwed for lack of better words.

Can anyone tell me if I will need to REMOVE this layer and reapply?

[RTflorida]

Re: Greetings from NY

I wish I could guide you further, the water repellent vermiculite is beyond my area of expertise. I followed the recommendations of several other forum members and stayed away from it. Hopefully someone who has actually used it can share their experience.
My latest guess is this is the reason your insulating layer appears more brown than grey....the portland not binding to the vermiculite has allowed most of the portland to settle to the bottom allowing the vermiculite (which is more brown in color) to rise to the top. Again, having no experience with this situation, I don't know how detrimental this is...I will stop short of telling you to do it over, until someone else chimes in...but I would consider it.

RT