No announcement yet.

40" oven build with questions I couldn't find answers to.

  • Filter
  • Time
  • Show
Clear All
new posts

  • 40" oven build with questions I couldn't find answers to.

    So first post, The oven is starting to get real, was able to buy hundreds of Diablo fire bricks, (3800 degree fire rating) it’s their third/fourth life, they came out of a sugar refinery and then was used for a huge Kiln for a notable artist. And then was dumped, and buried on the side of a house infested with cockroaches… Yes it was disgusting, there was thousands of them with the bricks. I Sealed my trailer and then bombed them for days. Power washed them, and then ground and or cut the bricks outer layer off, so no more standard size. Now the bricks are in San Francisco, and I’m pre-cutting them for a 40” oven, that will be built in Mazatlán Mexico for a commercial Pizza oven in my art gallery. along with those bricks I have hundreds of k-26 ceramic bricks. I am planning on using for insulation. I searched all the post but couldn’t find anyone using full bricks only half bricks, they way I read it is if I use full bricks I should be able to retain more of the fire’s energy. I am shaping them for a very tight fit with only 1/8 mortar joints.

    The oven size is 40” with a 20” dome, 20” wide door with a 12.6” high door 9” vent/Flew
    The igloo shaped oven will be surrounded by the Ceramic bricks and then back filled with perlite cement mixture, The finished shape will be a tall 6’ Diameter cylinder by 8’ tall the entire unit will be covered in broken sea glass and polished, (done this work before it’s a pain)

    ok now questions
    Has anyone used full bricks, couldn’t find any post on the subject.
    will one layer of k-26 ceramic bricks be enough for the floor insulation? Or do I have to place them on their side for a 4.5” insulation?
    Does anyone know the R Rating of k-26 bricks per inch”
    Is the opening too wide at 20”
    Is my math right or can the opening be taller?
    Can I thin set glass tile to ceramic bricks or do I need a stucco the exterior also
    This will be set on the 5th floor of my building, it’s a heavy concreate constructed building that was reinforced with 12” i beams, it was the old ballet school and was used as a bomb shelter, so I don’t foresee the weight being a issue. At the moment the 5th floor is open, but sometime in the future I will be add another floor and this will seal off the floor with the oven, so Im hoping to be able to vent it to the outside wall.

  • #2
    This will be interesting to follow so be sure to post a lot of pics.


    Door height is correct 63% of dome height 20 x .63 = 12.6, could go up to 65%. Width is builders choice, height is what is critical.
    Just to confirm, the k26 are really light weight. AKA IFB, in general they have a K rating (thermal conductivity) of 0.193 w/mk at 550C, comparing to CaSi Thermal Gold 12 is 0.086 wm/k. This mean the IFBs are about 1/2 as thermally effective as CaSi. Since you have quite a number of IFB bricks you might consider a couple layers, one on edge, second on flat giving 7" of insulation or abt 3.5" of CaSi equivalent.
    What did the artist use the kiln for? You have to careful of what was fired in the kilns due to residual heavy metals, IE Low fire glazes, usually really bright colors, may have lead in them.
    Full depth fire brick on dome will work but it is a ton of thermal mass and will use a lot of fuel to heat up. Unless you are doing production bread making it is really too much mass, stick with half bricks and insulate well.
    IFB are very soft and do not have the structural strength alone for the cylinder or use for attaching tile/glass
    Google Photo Album []


    • #3
      I tried to look up the thermal conductivity of the k-26, but found no data, doubled on the bottom seem a bet excessive, most people use perlite,base which should have a higher thermal conductivity, is that correct? well I knew they were not strong I can pour 2-3" of concrete around the entire cylinder, reusing the forms that I will have to make for the base, Thank you, good to know about the door, does the door have to be arched to make that percentage number or can I use heavy angle iron to hold up the opening bricks and have the opening straight across like a rectangle? either way it will more or less look like the photo when done


      • #4
        You can do what ever you want, just making suggestion based on k values of material.

        P/V crete 5 to 1 (which is typically used under a floor and more structural) is .72 to .75 in English units which is about 0.12 in Metric units so a IFB of 0.193 is just abt 1.75 time more thermally conductive than 5 to 1 p/v creter. See attached chart.

        Here is another manufacturer of K 26 IFB, K value is slightly better than I originally posted but in the same general range.

        Several builders have used angle iron for the lintel over the door. You just need to make allowance for the steel to be able to expand and move due to the high expansion ratio relative to the fire brick. It is is set solid into the brick, cracking could occur.
        Google Photo Album []


        • #5
          Thank you for the information, well that wont work for a floor insulator, thank you this is where a bit of info goes a long way. , so I will use the k-26 on the outside of the build, and back fill the void with P/V crete and use 4" of PV crete for the floor insulation, have you ever worked with PyroGel, hps, the thermal conductivity for this is .35, , I know I can weld pipe with a bare hand with a thin sheet of this to insulate myself from the arcs heat... and it wont retain water I can lay a layer under the floor bricks but it only does 1200 degrees don't know if that's enough, but I dont think the floor gets to 1000 degrees, I know the dome gets to 800+

          also should I wrap the oven with a blanket before back filling the entire dome to allow for expansion of either the PV crete or the fire bricks so I dont get expansion crack/explosions??


          • #6
            Karangi Dude did some temperature test on floor bricks via thermocouples, just going by memory, the bottom to the fire brick floor never approached anything close to 1000 F. Do a search under Karangi Dude for this post/info. Since you are enclosing the oven in a cylinder, why not use dry perlite or vermiculite for backfilling the dome, it will have a higher K value than a p or vcrete and weigh substantially less.

            Never worked with PyroGel but did look at specs, good K values (standard units). Kind of soft on the compression end but it isn't very thick either. After reading your intro again and the oven being enclosed, the potential of water migration is greatly diminished plus it is inside. I do not think wet insulation will be an issue. Why use both k-26 on the flats over 4" of 5 to 1 pcrete, then you will have a highly insulated floor.

            Google Photo Album []


            • #7
              I could use both, but then not much room for wood storage, as many people ask how much does it burn, and that is a question that is answered only once it is built, so I need to make sure there is room for wood.

              The building will be an open to mother nature for a few years while I get the permit to enclose the building as it is a historical landmark and they don't like changes. The building is set on multiple levels 7 in all, Most of it houses the art gallery with one floor for the toy tigers.(No they are not roaming around.) the top floor is going to be a restaurant and the oven is on of the expansive outdoor decks one half floor below the restaurant. The building doesn't lend itself to storage very well as the room are huge but no areas to hide anything, Next to the Oven will be a huge charcoal grill and then a plancha ( a stainless flat grill) in front of the area will be 2 eight foot refrigerated pizza tables and 2 sinks.

              once the entire oven is built it will have a water proof layer of glass on the outside and top of the oven, should I concave the top and add a drain? I will cross that question once Im on site and ready to pour the top

              The soft bricks k-26 will be used to hold back the p/v create, easy to cut on a template as it will be all the same cuts, and I already own them (for better or worst) I wont have any issues with expansion k-26 to the p/v creat, but I think I will have issues from the fire bricks to the p/v crete causing cracking, am I right to think that and do I need a blanket between the layers to allow for expansion of the fire bricks?

              Most of the equipment is already on site, the oven is being fabricated in a spare bedroom here in the states (the floors are PVC not wood) as labor is cheap in mexico but tools and other items are either expensive or unattainable, like a simple cup grinder. once the entire unit is fabricated I will number each piece and put them on huge dish carts, We normally have 20 workers to unload the trucks when I go, they will not be happy to see all the bricks.

              I am half done with the oven floor bricks, about 4 more hours....


              • #8
                are you saying just uses loose perlite? inbetween the dome and the k-26 brickwork. it would be easier and faster and should work....


                • #9
                  A lot of builders who have enclosures on their ovens have just poured dry perlite or vermculite over the ovens. If possible you should have some type of access to add more in case of settling. Either product has almost zero K values and relatively cheap. You might want to do a test on the K26 to see how well tiles/glass adhere to the brick.

                  Just saying, full brick walls will take a lot longer to heat and use substantially more fuel but once hot will stay hot for a long time. So if you are going to be in production mode then high amount of thermal mass is good but if not, one can easily get several days of cooking with half brick dome walls with the proposed insulation.
                  Google Photo Album []


                  • #10
                    Thank you, I will place a few pvc threaded caps on the top of the dome for filling,


                    • #11
                      Im following the build of a Beech oven, Although they are a cast oven, they have a much higher thermal mass than FB or other ovens, on average they are triple the mass weighing a ton for the dome alone without facade. then again they are about 100k USD and up. fully assembled.


                      • #12
                        I understand on a half brick its of no consequence as the gap isn't really that big, but Because I am using full bricks each row needs 1.5" of mortar, it seems excessive for the joint, and depending on what you read it may be too big of a joint, can I use high temp refractory clay, or is is better to just cut wedges from hole bricks? how dose it differ in the work ability, and is there a work ability difference from med grade to high grade I know High grade will have more aluminum, take higher temps and be harder once finished, but have never worked with the stuff, does it glue the bricks together well.. ie sticky, or does it just slide off and or create a low adhesion? is it gray, yellow or red? do I have a choice of color?


                        • #13
                          I think bricks are easy to saw....mine are wedges. Each row is the same number of pieces so there is a running bond all the way up and it looks pretty nice like that....I wish I could take credit but all I did saw saw what I was told to saw, it's my brother's work.


                          • #14
                            some bricks are easier than others, these diablos are very hard. that said I will do what it takes to make a close to perfect job, do i insulate the deck from the dome?


                            • #15
                              Not to get off the subject too much, but not all bricks are easy to cut/saw. True, low and medium grade bricks are relatively easy to saw but super duty (which I used in my case, they were surplus from a steel mill) are not. I went through a baker dozen of diamond wet saw blades in my build.

                              Back to wedges, some builders have made wedges to fill in the back side gaps. Can't comment on commercial refractory mortar since I used homebrew. But I do recall the David S says Alumina Calcified mortar flashes really fast.
                              Last edited by UtahBeehiver; 09-17-2018, 03:10 PM.
                              Google Photo Album []