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Question about cracks - Forno Bravo Forum: The Wood-Fired Oven Community

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  • Question about cracks

    I am sure this question has been asked and answered several times. I have looked through the threads, but unfortunately the search function on the forum doesn't seem to recognize compound words like "cracks in dome", instead it searches for anything with "cracks" and "dome"... which is virtually every post.

    So I do apologize if this is redundant.

    I was doing pretty well with curing my oven, got to 500deg w/o cracks. Today, I was going for 600deg and got distracted by my daughter. When I checked the temp the fire was up to 850deg. I quickly spread it out to reduce the heat. In examining the outer part of the dome, I noticed a couple cracks. Nothing major IMO but about 1/16in max. (see the pics below)

    My question is what are acceptable cracks and what are problems. Should I think about patching them or is a certain amount to be expected.

    Incidentally, when the outer part of the dome got warmer 100+deg and the inside cooled a bit, to 300deg the cracks seemed smaller.

    The dome seems solid and there isn't anything loose.

    Any thoughts?
    Attached Files

  • #2
    Re: Question about cracks

    Enclose it in quotes, like you did above and it works.

    Comment


    • #3
      Re: Question about cracks

      It seems like it still searches for only both words, but NOT the phrase. If no one wants to answer because it has been answered before, I get it. But I have been literally been looking for a good portion of the day and can't find my answers.

      Even if someone can refer me to an existing thread, that would help.

      Comment


      • #4
        Re: Question about cracks

        Make a slurry of mortar and paint it into the cracks, do it while the oven is warn to hot and expanded, this will fill the cracks.
        The English language was invented by people who couldnt spell.

        My Build.

        Books.

        Comment


        • #5
          Re: Question about cracks

          Almost all brick oven crack to a degree. Judging by your photos, yours has cracked a bit more than most. I don't think you have to worry though. Patch it up as brickie suggests and monitor it closely for the rest of the curing firing process. Check the inside, what you should watch for is if any bricks appear to have dislodged inward.

          Comment


          • #6
            Re: Question about cracks

            You're pictures might be deceiving me - but it looks like you can still see some moisture in the joints at the top of the oven. Is that the case - or is the mortar just a different color?

            I'm not sure about your case - but I think some people get in a rush to light a fire once the dome is done. The mortar might appear dry - but it's still gaining strength for quite some time. I've read that mortar should moisture cure for a week or so. With a WFO - you're not just putting that mortar to "normal" use - its much more extreme.

            I let me oven bake in the sun for weeks before I started any curing. Then - I went to an electric hotplate for a couple of days - then on to fires. I didn't measure fire temperatures - because fire temps raise / lower significantly with airflow and fuel changes - even when you just turn the logs over.

            I would try to patch the cracks as much as possible - but it's really not going to "fix" the cracks. When you apply the mortar when the oven is "warm," the moisture is going to be driven from the mix - and you wont get much strength out of it. I almost think you'd be better off with a fireclay slurry - and let that get down into the cracks.

            I would also wait to insulate until you've had an opportunity to fire the oven up at least once to full temps for an extended period. That'll tell you what the real impacts of those cracks are. Might not be much at all - then you can just cover with insulation and go from there.

            Pizzas will still taste as good . . .

            Comment


            • #7
              Re: Question about cracks

              The reason for a warm patch up is that the oven/crack is already expanded and the slurry will fill the expanded crack, if you patch when its cold the oven will expand and so will the crack.
              The English language was invented by people who couldnt spell.

              My Build.

              Books.

              Comment


              • #8
                Re: Question about cracks

                Originally posted by brickie in oz View Post
                The reason for a warm patch up is that the oven/crack is already expanded and the slurry will fill the expanded crack, if you patch when its cold the oven will expand and so will the crack.
                I don't disagree with the method at all . . . I'm just pointing out that a warm/hot oven will result in a rapid moisture loss in the mortar which will likely mean it will be very weak. I was wondering, out loud, whether a slurry of fireclay would work as well - maybe better. I don't know . . . I'm just thinking out loud.

                Don't you think some of that mortar looks damp???

                Comment


                • #9
                  Re: Question about cracks

                  Originally posted by Cheesesteak View Post

                  Don't you think some of that mortar looks damp???
                  Some of it looks damp to me.
                  The English language was invented by people who couldnt spell.

                  My Build.

                  Books.

                  Comment


                  • #10
                    Re: Question about cracks

                    It does look a little damp in places to me too. The dome was completed 3 weeks ago. I let it cure damp for 1 week, then took the blanket off and let it sit for another week. I live in the San Fernando Valley (Southern California) and it has been about 90+ deg so I don't know why it would still be wet... particularly toward the bottom. The bottom was done 5 weeks ago.

                    I need to let the inside cool to check if the crack goes all the way through.

                    I do appreciate all the input.

                    Chris

                    Comment


                    • #11
                      Re: Question about cracks

                      Upon further inspection, the crack does go through to the inside of the oven. It is, oddly, only on one of the chains, the rest look fine. I wasn't noticing any smoke coming out, but I did patch the outside.

                      It feels pretty solid, I don't feel any loose bricks. Should I press on and continue my cure, or should I not? I hope this doesn't mean I have to dig out and re-mortar, re-cure etc... but if it does, so be it.

                      Thanks,

                      Chris

                      Comment


                      • #12
                        Re: Question about cracks

                        I fairly sure it wont collapse so patch the outside and press on, itll still cook ok.

                        It actually takes a lot to get brickwork to fall over if there are no lateral forces at play.
                        The English language was invented by people who couldnt spell.

                        My Build.

                        Books.

                        Comment


                        • #13
                          Re: Question about cracks

                          Problem with a thin slurry is that extra water means more shrinkage. A clay only mixture is also going to result in high shrinkage. If you can add about 50% aggregate (finest sand you can get) it will result in a mix that won't shrink too much.
                          Kindled with zeal and fired with passion.

                          Comment


                          • #14
                            Re: Question about cracks

                            "It feels pretty solid, I don't feel any loose bricks. Should I press on and continue my cure, or should I not?"

                            Carry on. Keep an eye on any changes, loose bricks, or crack increases, but I think you will be OK.

                            Comment


                            • #15
                              Re: Question about cracks

                              Thank you guys so much for your input. On further inspection, I don't think my crack goes through to the inner part. At the chain that has the crack, I switched from using my "indispensable tool" to a form so I wasn't able to clean the mortar off as well as the lower chains. As a result, there is a bit of mortar standing proud from the bricks which makes it so the soot has a void.

                              I am at 1 week, 6 fires up to 650deg. I am away this weekend so I put a high wattage bulb for a couple days. No further cracks, my patches are holding. When I get back, I will insulate and finish the enclosure.

                              In the home stretch.

                              Comment

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