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42" Pompeii Oven in Jamaica

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  • wthwaites
    replied
    Thank you both for the advise. Feedback like this is why I love this forum and its members.
    I don't want to stop the process now. I just got a infrared temp gun and fired up to 500o F today; 3 days left until 800o F. I can make the repairs in the future by either one of these recommendations or purchasing a double walled chimney; we'll see...
    Last edited by wthwaites; 01-11-2021, 05:19 PM.

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  • david s
    replied
    "Drying" and "curing" are two different things. Curing is a chemical reaction. Portland based masonry products should be allowed to remain moist for at least a week to properly cure in order for it to achieve some of it's final strength. (28 days is best) Then it can be allowed to dry. "

    Hi Gulf, glad you posted this, I dislike the the term curing as it's used in the curing thread, because it gets confused with damp curing of various types of concretes, renders/stuccos and mortars, where the objective is to retain sufficient water for a period to allow for the hydration process to enhance strength. I much prefer the term "water elimination" as the drying fires applied to an oven on completion never reach high enough temperatures to change anything chemically, all we do is remove the mechanical water.

    Regarding the cracks surrounding the flue pipe on the outer shell, this is a common problem if the render/stucco is formed directly around the pipe. Because the steel of the flue pipe is way more conductive than the stucco that surrounds it then it will expand first creating stresses in the stucco. If the pipe is surrounded with some box cardboard and the stucco worked up against it, then it can be removed leaving a gap of around 5mm which can be filled with high temp silicon. This seems to do the trick, allows the pipe to expand a little and eliminates the cracks which can otherwise create an entry point for water.

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  • Gulf
    replied
    "Drying" and "curing" are two different things. Curing is a chemical reaction. Portland based masonry products should be allowed to remain moist for at least a week to properly cure in order for it to achieve some of it's final strength. (28 days is best) Then it can be allowed to dry.

    If it were mine, when I made the repair, this is what I would do.

    Remove the rendor/stucco back from touching the single wall pipe so there is no heat transfer. Cut a short piece of larger diamenter galvanized pipe to make a very short section of double wall. (Trimming the Render/stucco layer back enough to insert it slighty may be easier than scribing the bottom of the outer pipe to fit). Insulate between the pipes. Render/stucco up to near the top of the outer section. Then purchase or fabricate a storm collar to place over the intersection of the two pipes.

    You can do a search of the forum for "storm collar" . That should pull up some examples.

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  • wthwaites
    replied
    I don't think so. I had it sitting for about 3 days before starting the cure fires. The cracks are mainly around my chimney with is only a single wall, so I assume that's the main reason for them.
    I operating under the assumption that once the curing is done, I can do another render to fill whatever cracks there may be.

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  • MarkJerling
    replied
    Do you think that render was still quite wet?

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  • wthwaites
    replied
    I'm at a 350o F Cure today, which was achieved. I may have gone a bit over but not by much. The thermometer installed in the door shows 350o F, but a oven thermometer i placed on a firebrick inside beside the charcoals showed 380o F. Either way, I closed the door and left it alone from there for it to cool down.
    I did not see any cracks inside the cooking dome, but I noticed a few cracks at the top of the outer dome render where the chimney is installed. Its shown in the pic. I have all my steam vents open so there shouldn't be much pressure. Maybe I did not put enough render in this area? I assume that I can just do another render over the general cracked area after curing.
    What do you think? Is this bad?

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  • wthwaites
    replied
    Awesome, Thanks!

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  • Gulf
    replied
    OK. Great start! If you don't have a blast (draft) door, you can place the door partially closed during the burn. That will give the charcoal enough O2 to burn while holding more heat in. That will bring the temps up even more for a 3rd or 4th day. It would be best to get a closing day temp about 30 minutes after you fully closed the door. But, you are doing just fine.imo.

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  • wthwaites
    replied
    Originally posted by Gulf View Post
    Are you using paper to start the the charcoal inside the oven?
    Newspaper - More for ohhhhs and ahhhhs

    Yesterday - I started the charcoals outside and then shovel in when fully lit. I did put a few crumpled pages newspapers in but only a small amount (maybe 4) just to see some small flames.
    Today - Same starting process but I also lit two pages of newspaper to start some leftover charcoals that died out inside the oven when I closed the door last night after getting to 200 F. Today I got to 265 F and then closed the door.
    Last edited by wthwaites; 01-07-2021, 06:07 PM.

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  • Gulf
    replied
    Are you using paper to start the the charcoal inside the oven?

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  • wthwaites
    replied
    Day 1 Cure Fire! - Using the charcoal method.
    I can't find my infrared thermometer, but I believe i got it up to 200 F. I doubt it went any higher in temp...
    Will try get up to 250 tomorrow!

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  • wthwaites
    replied
    Thank you. Will do some more research and will most likely start off the cure fires this way . Can't wait!
    Last edited by wthwaites; 01-05-2021, 05:24 AM.

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  • Gulf
    replied
    ....The FB guide advised not to use coal in the oven...
    To my knowlede, this is Forno Bravo's latest statement about the use of coal in their oven's.
    .....I do have access to lump charcoal (Logwood), so it can be done with ease. Can you provide some details on this method?
    Do a search of the forum for "heat beads charcoal" Lots of examples and pics in the various threads as well as some explainations. But, basically, it is starting charcoal in a charcoal chimney starter outside the oven. Then placing the fully started coals in the oven. Heat, but no direct flame impingement on the dome. I used a blast (draft) door to help hold the heat in the oven while giving the charcoal just enough O2 to burn. I have found out since that placing the coals on a slightly elevated grate also helps. If you use a blast door and elevate the coals you should be able up to achieve day 3's temps from the schedule thatdavid s linked. That with no worries about a direct flame impingement on the dome. Note that lump charcoal burns a little hotter than charcoal briquettes. Also, it takes alot of charcoal to do this method.
    Last edited by Gulf; 01-04-2021, 09:41 AM.

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  • wthwaites
    replied
    Update:
    I put on the finishing coat of Stucco. Also added some color pigment to the mix but messed up at the end when evening out the shape over the chimney flue area.
    Trying to figure out how to fix that bit; I believe that applying an acrylic paint would be easiest instead of doing another stucco layer.

    That aside, I believe that we are ready for cure fires! Do I have to wait a full week to start, or can I start earlier?

    Aside from cure fires, my next step is to install a granite landing at the front. I figure I can install this during the curing stages (hopefully). If not, I will wait to install until after the cure fires...

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  • wthwaites
    replied
    Originally posted by david s View Post
    Thank you!

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