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  • Clay Ovens

    Hi y'all!! I'm new to the forum, but have had a clay oven for about 6 years now and am thinking about making some changes to it. The positives are that it was real easy to make, with low cost (I paid a mason to make me the pedestal; otherwise all else was free from Mother Earth). The negatives are that clay is weather (and bug!) susceptible and needs to be protected. So, if anyone has any experience here (like any particular coatings that have worked as a weather barrier) I'd be interested in your experiences! Thanks!

  • #2
    Re: Clay Ovens

    Hey luca, welcome to the forum!

    I'm afraid I can't help with your clay oven questions, but I would be interested in more info about your oven. How big is it? How did you make it and what plans did you follow? Is it insulated in any way? How hot does it get and what do you cook in it? And (maybe most importantly) could you post some pictures?

    We've had lots of people asking about clay ovens here, and it sems like such a good solution for people working on a low budget - so it'd be really really nice if you could provide some first hand information.

    One idea, maybe you could build an enclosure round your oven to protect it? With a tile roof, like a lot of the ovens here have.
    "Building a Brick oven is the most fun anyone can have by themselves." (Terry Pratchett... slightly amended)

    http://www.fornobravo.com/forum/f8/p...pics-2610.html
    http://www.fornobravo.com/forum/f9/p...nues-2991.html

    Comment


    • #3
      Re: Clay Ovens

      Or put a superwool insulating blanket over your dome, cover with chicken wire and then render it!
      The insulation would obviously help to hold the heat but more importantly act as a medium between the baked clay and the hard water proofing.

      Oh hi Luca, by the way and welcome aboard.

      Neill
      Prevention is better than cure, - do it right the first time!

      The more I learn, the more I realise how little I know


      Neillís Pompeiii #1
      http://www.fornobravo.com/forum/f8/n...-1-a-2005.html
      Neillís kitchen underway
      http://www.fornobravo.com/forum/f35/...rway-4591.html

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      • #4
        Re: Clay Ovens

        Hi!

        And I'm afraid I can't offer anything experience wise either. My plans are to build an oven out of cob (clay) but it will be a while yet before I get started. At this point. I'm planning on an enclosure, possibly of papercrete with a sealant.

        I'm curious about what kind of problems you've had with bugs. But anyway, welcome aboard!
        "He is no fool who gives what he cannot keep to gain what he cannot lose." - Jim Elliot

        "Success isn't permanent and failure isn't fatal." -Mike Ditka
        [/CENTER]

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        • #5
          Re: Clay Ovens

          I'd be glad to share my experiences with clay ovens (and will post some pics if I can figure it out!) A classic book on clay ovens is Bread Ovens of Quebec by Boily & Blanchette (it's out of print but available on the Internet). I used this for the clay mixture and construction methods, but came up with my own design and size since their ovens were gigantic (they could bake 30 loaves at a time for a week's worth of baking!). These classic ovens were bee-hive shaped, with the entrance 63% of the height of the interior dome height (a "magic formula" which gives best air circulation during firing, according to their research on scores of ovens). What I found most interesting is that they were all made of local clays dug by the builders near the ovens, which is exactly what I did here in KY (no commercial clay or specialty clay brought in from elsewhere). The only item that might have been purchased were the actual doors and door frame, which are usually an arched metal frame with two door panels opening in the center; otherwise, everything was made from local materials (e.g. a base was assembled out of large field stones, upon which was poured a concrete slab for the floor of the oven; then the rest was local clay). More later as I'm out of space!!
          Attached Files

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          • #6
            Re: Clay Ovens

            Originally posted by nissanneill View Post
            Or put a superwool insulating blanket over your dome, cover with chicken wire and then render it!
            The insulation would obviously help to hold the heat but more importantly act as a medium between the baked clay and the hard water proofing.

            Oh hi Luca, by the way and welcome aboard.

            Neill
            This is a possibility, but I'm not sure what a "superwool" blanket would be (e.g. ordinary house insulation?) and what do you mean by "rendering" it?

            Comment


            • #7
              Re: Clay Ovens

              Originally posted by Archena View Post
              Hi!

              And I'm afraid I can't offer anything experience wise either. My plans are to build an oven out of cob (clay) but it will be a while yet before I get started. At this point. I'm planning on an enclosure, possibly of papercrete with a sealant.

              I'm curious about what kind of problems you've had with bugs. But anyway, welcome aboard!
              Bugs love dirt/clay, which means if you cover it too tightly (especially say over the winter) cockroaches and other lovelies start boring holes in the clay for their nests! The solution so far has been to uncover periodically during warm days to expose the creatures to sun and predators, spray under the tarp with a bug spray,(not something I want to do frequently), or fire up the oven (which of course kills everything!).

              Comment


              • #8
                Re: Clay Ovens

                Luca,
                superwool refers to a refractory insulating blanket, there are many manufacturers, most are comprised of ceramic fiber material - its sole purpose is insulating. All of this leads to a question - what are your heatup times and how well does your oven retain heat? A brick of refractory masonry oven needs as much insulation as possible to be worthwhile and effective. At least 2 inches of blanket, 3+ inches of vermiculite or perlite concrete, or a combination - blanket + vermicrete/perlcrete.
                I have ZERO knowledge on Clay/Cob/Mud ovens, so I can't say whether you need insulation (I suspect it will help greatly)

                Render refers to a finish layer of a weatherproof concrete - commonly referred to as stucco. Pretty cheap whether mixed yourself or dry premixed available at you local Home Depot/Lowes. If you go with the premixed, get the one with the acrylic additive - as others have said, it is nearly "bulletproof" and easy to work with.

                RT

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                • #9
                  Re: Clay Ovens

                  Hi,

                  I love the pics. Thanks for sharing! One question though, why two openings? I assume the wooden thing in the background is some kind of roof that you put over it. Are you using a tarp as added protection? (Okay, so that was two questions...).

                  Note to self: make sure to use oven regularly! Bugs are icky!
                  "He is no fool who gives what he cannot keep to gain what he cannot lose." - Jim Elliot

                  "Success isn't permanent and failure isn't fatal." -Mike Ditka
                  [/CENTER]

                  Comment


                  • #10
                    Re: Clay Ovens

                    Welcome Luca,
                    If you are simply looking at inexpensively waterproofing and bug proofing the outside of your oven you might look into whitewash or milk paint. Here's a link:

                    homestead recipes

                    Whitewash has been a traditional method of keeping bugs out of structures and making them waterproof. It's cheap and can be colored so the soot from the fire isn't as dramatic. Milk paint is the old standby that wooden barns were painted with and if you follow the link they have some good info on some combinations of the two (whitewash and milk paint).

                    I have a bit of a problem with spending a significant amount of money on ceramic insulation for a mud oven. By design mud ovens are inexpensive to build or rebuild as the need arises. Same issue with spending time and materials for rendering.

                    Again Welcome to the forum,
                    Wiley

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                    • #11
                      Re: Clay Ovens

                      I guess that I just don't understand the whole clay oven concept...If they are self insulating and can reach and hold pizza temps or retain enough heat for roasting/baking, thats great. If they require continuous firing for all aspects of cooking because they don't hold heat...that is just dark ages inefficiency and very costly to anyone who does not have an endless supply of free wood.
                      I also don't understand it not being worth the cost of insulating or render/stucco. I have less than $100 in insulation costs in my oven (including 2" of Insulfrax purchased on ebay for $19). 2 80 lb bags or premix stucco will set you back a whopping $30...sure seems reasonable if it needs insulation (again, I have no clue if it does) and a protective coating. I'm a firm believer in working smart, not hard. Building, tearing down, and rebuilding just does not seem smart to me, even if it just means slinging around Clay mud.

                      I understand budgets may be tight, but there are several examples of brick ovens on this forum that were built on the cheap...Dave being the most recent and famous (I think his entire oven came in around $500), Redbricknick (old member) did a very cool designed oven for FREE, his only cost was the pennies (YES, Abe Lincoln 1 cent pennies) that he chose as the finish to his igloo; everything else he obtained using the barter system.
                      The only thing I guess I understand is the idea of getting back to nature and using a simple product of mother earth -thats fine, just not my cup of tea. To me, its not about the oven or the process.....its the great food I will be producing (worry and work free) for years to come. Although I enjoyed my build, it was no different than any other project...get it done in a reasonable time frame, make it fuctionally perfect as I can, and save as many $$ without compromising functionality, practicality, and aesthetics.

                      Sorry for the long disertation.....I'm just trying to get a grasp of the idea and understand the benefits and/or negatives of a clay oven.

                      RT

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                      • #12
                        Re: Clay Ovens

                        After reading a book about them this week, I had an urge to build a cob oven in a spare corner of the garden, just a little one built as part of a stone wall or bench or something. They do look very cool and I like the idea. However if I do make one I was thinking that vermiculite-concrete would be the insulation of choice. Or if you want to stick with the au naturale theme, lime mortar with vermiculite?
                        My oven: http://www.fornobravo.com/forum/21/t...html#post46599
                        My blog: Live For Pizza

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                        • #13
                          Re: Clay Ovens

                          Didn't John Fahle and his friends insulate their oven with a sawdust mixture? (And don't ask me how that works, but apparently it did.)

                          I like the idea of clay ovens because I think it'd just be so cool to dig up the necessary materials out of the garden - it'd be really interesting to compare the performance with a brick oven, too. Benifits/negatives, I just don't know RT. Maybe that's why I'm interested? We've also had a couple of questions from third world countries, where it seems like it'd be a usefull skill to have, building a mud oven I mean.

                          If I built a mud oven, I think I'd go wth the vermcrete and stucco finish and fire it up once a week or so to keep the bugs out... well actually I'd do a lot of reading first and then decide.
                          "Building a Brick oven is the most fun anyone can have by themselves." (Terry Pratchett... slightly amended)

                          http://www.fornobravo.com/forum/f8/p...pics-2610.html
                          http://www.fornobravo.com/forum/f9/p...nues-2991.html

                          Comment


                          • #14
                            Re: Clay Ovens

                            Hi,

                            My own interest is historical, that and they're cool. Cob ovens have no difficulty holding temps - they're made of the same material as brick, the brick is just fired in place instead of being fired in a foundry. As far as the need for insulation, it depends on how thick the oven is made. It's quite possible to make the walls so thick that they require no further insulation.

                            It's a myth that the dark ages were invariably inefficient. Think about it, if you had to go cut, gather, store, and then fetch all the wood that you would need for an entire winter - not just for the cooking but heating as well - wouldn't you use the most efficient materials that you could? Medieval technology was surprisingly efficient for its time. Properly build cob homes are actually very energy efficient. There's no reason that a cob oven wouldn't also be fairly efficient.

                            I'm honestly not sure which would be more efficient brick or cob. Firebrick would certainly have better refractory properties, but it would also have mortar. As I understand it the refractory properties of cob would depend largely on the type of clay used and the amount of silica present so there would be some variance there but there would also be no need for mortar.

                            Cob also has some significant advantages in construction besides cost. Tools required are not particularly specialized and indeed only a very few are actually necessary. Trowels and cement mixers make it easier but they're not essential. There's no need for specialized saws and if you do make a mistake it's much less expensive to tear down and rebuild than a brick oven would be.

                            At the end of the day I think once one isn't particularly that much better than the other. It depends on your actual needs and intentions as to which one will work out the best for you. For industrial kitchen I suspect brick would be far superior to cob simply because you have better control the refractory properties. For a backyard oven only to be used occasionally cob may well be the better bet just in terms of time and expense.


                            For me, my choice of cob is severalfold. It's historically accurate for the medieval period (some other time time I'll explain why that matters to me), it's much easier to work with, which means it will match my skill level, it's less expensive to build and I just think it's cool.

                            Okay, I think maybe I should stop the dissertation now... Me? Get carried away? What makes you think that?
                            "He is no fool who gives what he cannot keep to gain what he cannot lose." - Jim Elliot

                            "Success isn't permanent and failure isn't fatal." -Mike Ditka
                            [/CENTER]

                            Comment


                            • #15
                              Re: Clay Ovens

                              Thanks for all of the interesting ideas! As for Whitewash, I tried that about 4 years ago and it slowly disintegrated over time; in part from beneath, since ambient moisture/humidity is always influencing the water content of the outside (unfired part) of the oven. I've also built a wooden cover which worked OK, but got blown off once or twice in storms!. As for heating capacity, I love cooking pizza and can fire my oven up to 800-900 degrees (great pizza needs very high heat) with very little wood!! (I'm talking about 4-6 2x4 size pieces of wood 24 inches long for the whole 2-3 hour firing process). I have also experimented with slow-cook barbecue by placing a pan with meat and barbeque sauce in the oven overnight with a door on the oven with excellent results. My particular oven was started as an experiment and has walls only 4 inches thick, so the heat retention is only several hours, but the classic Quebec bread ovens would have walls from 8-10 inches thick, thus giving a much better heat retention (and in those days they had no insulation on these outdoor ovens). As for construction, I'm attaching a few more pics. My oven floor is only 24 inches by 36 inches, and in my first attempt, I incorrectly placed the door in the side of the oven, thinking I could get more "stuff" in it. That totally ruined the aerodynamic properties, and thus the hot fire/smoke would not circulate properly, causing start-up and cooking problems. This was easily solved by filling in the side entrance with more wet clay, and "drilling" a new hole (I just took a drill bit and punched 50 or so holes through the already dried and fired clay) at the end. This has worked beautifully in that the oven fires easily and I can crank the heat up by adding a small piece of wood a few minutes before before putting my food in. This is definitely the way too go for a no-cost oven, but I will look into the insulation ideas that have been mentioned.
                              Attached Files

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