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Newbie with salvaged vintage boiler/furnace for pizza oven

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  • Newbie with salvaged vintage boiler/furnace for pizza oven

    I think I'm creating a beast that may or may not be a great pizza oven. In any event it will look marvellous with 3 cast iron doors, and a stucco, terracotta look exterior. The build though is going to be challenging and I'll probably post quite a few questions through the process. I'm guessing this might be the most appropriate section of the forum? I'm not sure if anyone else has tried this, but I'd like to hear about it if so

    The 'structure' is built for 4 chambers (even though I have to rebuild two of the interior 'floors'). Long ago it was modified from coal to oil. The cast iron doors are just too cool to mess with too much, other than heat paint. So my up to down plan is this: cook chamber, fire chamber, ash chamber, wood storage (no door).

    The stove is between 4 and 5 feet high, and has a nice shape. The exterior is some kind of asbestos I'm guessing as its probably 100+ years old. There is a kind of paint or whatever that holds the semi-soft fibrous insulation together, but it is fragile. Below this outer layer is a DOUBLE wall (1.5 to 2" space between) steel or cast structure that is the bones of it all and quite remarkable (very heavy duty). The whole thing is basically a water jacket. This leaves the possibility of filling it with some kind of extra insulation down the road some.

    My first task is to modify the top cook chamber. On the back side there is large flue opening, but the opening to this is inset to about 1/2 way into the chamber horizontally. The other half will be my cook area with a yet-to-be-determined type of cook base. The fire/gasses come up each side of this 'inner' flue and then horizontally into the opening. There are two large square tubes that criss cross the chamber and head to the ceiling double layer, so I've been cutting those out of the way with cutting grinders (not easy!). The base of the cook chamber is also the same kind of double wall water passage, so when I finish cutting out the square tubes, I'll also be cutting out the top layer of the base of this chamber. That still leaves me a dropped steel shelf to put in fire bricks or ??. As the fire will be below, I know its CRITICAL that I find a heat balance that will be hot enough to cook the the pizza bottom as well as the top. The flow of hot gasses through the chamber is yet to be determined as to suitability, so once I put this thing in place, I'll do some test fires to see how hot I can get it (including experimenting with different base materials). One nice thing about the lower steel plate (that is about a foot above where the fire will be) is that I could drill or cut holes in it to allow progressively more heat to the bottom of the cooking surface layer if that is what is required.

    I'll stop here for now....going to be a quite a project... pictures soon...

  • #2
    Looking forward to seeing the pics. As a word of caution, asbestos was commonly used of furnaces in the early 1900s as insulation and heat resistant material. It becomes very "friable" and if disturbed sends cancerous fibers all over the place. Removal/disposal requires certified asbestos abatement professionals. It is not for the DIYer even with PPE.
    Russell
    Google Photo Album [https://photos.google.com/share/AF1Q...JneXVXc3hVNHd3/]

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    • #3
      Originally posted by UtahBeehiver View Post
      Looking forward to seeing the pics. As a word of caution, asbestos was commonly used of furnaces in the early 1900s as insulation and heat resistant material. It becomes very "friable" and if disturbed sends cancerous fibers all over the place. Removal/disposal requires certified asbestos abatement professionals. It is not for the DIYer even with PPE.
      Yes, good advice. My intention is to simply encase it in stucco. When I'm 'tinkering' I'm wary of disturbance and have been wearing a good 3m respirator.

      I'm wondering what kind of insulating (cementitious?) material I could fill the water jacket with to better retain heat.

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      • #4
        Probably just fill it with loose perlite or vermiculite as the insulation should work fine.

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        • #5
          Originally posted by Pizzarotic View Post
          Probably just fill it with loose perlite or vermiculite as the insulation should work fine.
          Yes, that was my thinking as well. There is a water pipe exiting out the centre of the top which is an easy fill point - much later that pipe will be removed and maybe an ornament of sorts replacing it. Where I can, I'll jam steel wool into the lower half of the double wall jacket to block the perlite, as its not needed below the fire chamber.
          The carcass is finally being removed from my trailer tomorrow, so I'll be able to take a proper 'before' picture of it on its base.

          I think the perlite will be easier to pour into the boiler wall. It appears to be more pricey that the vermiculite, but the volume needed isn't huge.

          Thinking way ahead, I notice the cost of 1" thick refractory grade aluminum silicate insulation runs about 13 dollars a square foot in CDN dollars (Amazon.ca). Is this a reasonable outer insulation solution, given that there will be perlite inside the jacket and has existing coated asbestos on the outside (1/2 to 3/4 of an inch). The final outer layer will be stucco. A friend says rock wool might even work on the outer side below the stucco wire, but I'm not so sure.
          Inside the pizza chamber (above the fire chamber ), I will likely have firebrick top/bottom and sides, except for the heat/smoke entry and exit points of course. what technique will hold bricks on the inner ceiling of this chamber, given that it will be mostly flat?

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          • #6
            Hope I'm not repeating myself. Took a couple before pics (but after a lot of grunt work getting this very heavy cast boiler/furnace from someone's basement to my cement pad). Price was great anyway...freebie.
            I'm having to do some cutting and fabrication inside to install firebricks in the top cook area, make two fire/exhaust chutes on either side of the bricks, and the exit is straight out the back (then up). Just going by my best guesstimates (and a bit of research of course). The water pipe passages on top (taller pipe, and plug visible) are access points for pouring in perlite or Vermiculite. Not sure if the insulating material should be in a cement matrix or just put in dry?? Will be important to try and spread it out evenly to all sides.
            I also have to create bases or floors for both the fire box and the ash drawer, as its pretty much all open inside except for the top cook chamber.

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            • #7
              Originally posted by siestapizza View Post
              Thinking way ahead, I notice the cost of 1" thick refractory grade aluminum silicate insulation runs about 13 dollars a square foot in CDN dollars (Amazon.ca). Is this a reasonable outer insulation solution, given that there will be perlite inside the jacket and has existing coated asbestos on the outside (1/2 to 3/4 of an inch). The final outer layer will be stucco. A friend says rock wool might even work on the outer side below the stucco wire, but I'm not so sure.
              Ceramic fiber blanket is the best and probably your only option. The rockwool will need to be 4" thick.

              Inside the pizza chamber (above the fire chamber ), I will likely have firebrick top/bottom and sides, except for the heat/smoke entry and exit points of course. what technique will hold bricks on the inner ceiling of this chamber, given that it will be mostly flat?
              Nothing will glue them in place on the ceiling, you will need to physically secure them. Personally i would just leave them out.

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              • #8
                Originally posted by siestapizza View Post
                The water pipe passages on top (taller pipe, and plug visible) are access points for pouring in perlite or Vermiculite. Not sure if the insulating material should be in a cement matrix or just put in dry??.
                .
                Dry will perform much better.

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                • #9
                  Originally posted by Pizzarotic View Post

                  Ceramic fiber blanket is the best and probably your only option. The rockwool will need to be 4" thick.



                  Nothing will glue them in place on the ceiling, you will need to physically secure them. Personally i would just leave them out.
                  Thanks, yes agreed. I was noticing the blanket that FornoBravo sells on their site for what seems like a good price. I'll see if they ship to Canada.
                  If I decide to put firebrick on the ceiling of the cooking area, I would have to bolt a drop metal sill on the door side and rest the other end of the bricks on upright bricks at the other side. But as you imply, I could wait on that and just have bricks bottom and sides for now, as the top will already have a couple inches of dry matrix perlite sandwiched between the cast iron. As it turns out, its the top of the boiler furnace that is noticeable thicker than the sides, because it probably served as a reservoir for hot water before exiting out the top pipe.

                  As an aside, I found Perlite at a great price, about 1/3 that of Amazon, at a local hydroponics business.

                  I'm making slow but steady progress on the oven, but nothing photo worthy for now. I'm getting close to finishing the new floor for the burn chamber, and found a study metal flap cover that was unnecessary at the lower back of the stove base, and am using it for a trapdoor/ash dump at the rear of the burn area.

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                  • #10
                    Originally posted by Pizzarotic View Post

                    Dry will perform much better.
                    Perfect, I was hoping that would be best. Ii'll probably do percrete for inside the top two cast iron doors which have a substantial double wall as well.

                    I am going to try pouring Percrete crystals through two openings at the top of the oven, which I'll assist with a flow of compressed air to try an avoid 'jams'. There are two 2" pipe openings at the bottom of the stove in the rear which I can screen off so that air can escape while I pour. Will wear a good mask for this task as well.

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                    • #11
                      Sorry, meant to say will pour in Perlite crystals (not percrete in the oven itself)

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