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Post by oblertone on Jun 20, 2018 6:49:07 GMT
Multiple drying fires is the best way forward, building slowly over at least a week. It's also important to allow complete cooling between fires to encourage migration of water; 'going for it' after just one drying fire will almost certainly generate enough steam to cause severe cracks.
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mrjl
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Posts: 42
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Post by mrjl on Jun 20, 2018 8:10:25 GMT
Multiple drying fires is the best way forward, building slowly over at least a week. It's also important to allow complete cooling between fires to encourage migration of water; 'going for it' after just one drying fire will almost certainly generate enough steam to cause severe cracks. Great, thanks. I'll do a week of drying fires when I'm back in July and then, finally... pizza time!
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Post by kofi69 on Jun 20, 2018 16:23:36 GMT
Hi all. It looks as this build is along the lines of a mattone barile oven. I have tried to add a photo of the one I have created using their instructions, but not their kit. I must say I am a bit disappointed with it, as I cannot get to the magic 350 pizza degrees c like I am meant to. Probably operator error as it has only had three proper firings, but I really tried hard last week. Built with a 2 inch thick vermicrete base, kiln bricks all over and a 2 inch thick fibre blanket covered with stucco render. I wish I had built a dome! If you look at the mattone instructions, all mixes and materials are detailed. The structure is good, but the performance, at the moment, is underwhelming. If you would like more pictures of my build please ask. Cheers
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Post by kofi69 on Jun 20, 2018 16:24:57 GMT
Hi all. It looks as this build is along the lines of a mattone barile oven. I have tried to add a photo of the one I have created using their instructions, but not their kit. I must say I am a bit disappointed with it, as I cannot get to the magic 350 pizza degrees c like I am meant to. Probably operator error as it has only had three proper firings, but I really tried hard last week. Built with a 2 inch thick vermicrete base, kiln bricks all over and a 2 inch thick fibre blanket covered with stucco render. I wish I had built a dome! If you look at the mattone instructions, all mixes and materials are detailed. The structure is good, but the performance, at the moment, is underwhelming. If you would like more pictures of my build please ask. Cheers
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mrjl
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Posts: 42
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Post by mrjl on Jun 20, 2018 18:13:49 GMT
Should I have used waterproofer in the render? I didn’t but someone just asked if I did given that’s it’s outside.
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mrjl
valid member
Posts: 42
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Post by mrjl on Jun 20, 2018 18:49:10 GMT
Hi all. It looks as this build is along the lines of a mattone barile oven. I have tried to add a photo of the one I have created using their instructions, but not their kit. I must say I am a bit disappointed with it, as I cannot get to the magic 350 pizza degrees c like I am meant to. Probably operator error as it has only had three proper firings, but I really tried hard last week. Built with a 2 inch thick vermicrete base, kiln bricks all over and a 2 inch thick fibre blanket covered with stucco render. I wish I had built a dome! If you look at the mattone instructions, all mixes and materials are detailed. The structure is good, but the performance, at the moment, is underwhelming. If you would like more pictures of my build please ask. Cheers Hi. Thanks for commenting. It might be better for you to start your own thread detailing your build and issues, so that things don’t get confusing?
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Post by downunderdave on Jun 20, 2018 20:59:32 GMT
Should I have used waterproofer in the render? I didn’t but someone just asked if I did given that’s it’s outside. There are two schools of thought here. No waterproofing may let in some water, but also locks the water in making drying the oven more difficult. Italian ovens are traditionally finished with a lime render which is breathable and not waterproofed, they are also usually out in the weather. I think it depends a lot on your weather conditions. I live in the tropics and during the wet season because of the high humidity the oven gets wet even if it hasn’t rained because refractory materials are porous. If you want to waterproof it wait until it’s really dry. If you used a proprietary cement render they usually have some waterproofing added. You can tell this by their resistance to water when mixing. This should give the oven some partial waterproofing at the same time as allowing it to breath. You can also just paint it with acrylic paint, but again wait until it’s really dry or you’ll get blistering under the paint coating. Probably the best solution, but the most expensive, is to have a roof over the oven.
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mrjl
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Posts: 42
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Post by mrjl on Jul 8, 2018 20:38:20 GMT
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Post by downunderdave on Jul 9, 2018 2:19:31 GMT
It looks to me like you have rendered directly against the flue pipe. On heating, because the steel (I presume it is steel) pipe is way more conductive than the concrete surrounding it, expands first cracking the outer shell. Too late now but one solution is to wrap the pipe with some cardboard box cardboard, render up to it, remove it when the mix sets and fill the gap with high temp silicon. You may find an alternative solution perhaps with the creative use of an angle grinder and diamond blade. Filling the cracks with more render will put you back to square one.
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mrjl
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Posts: 42
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Post by mrjl on Jul 9, 2018 6:38:53 GMT
OK Dave, can I just paint the oven then? I’m not bothered about the cracks if they’re just superficial. Or would you recommend repairing as you described, patching the render and more drying fires?
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Post by oblertone on Jul 9, 2018 9:10:12 GMT
It's been said before but there are wfo owners who admit to having cracks, and there are owners who don't admit it, but there aren't any WFO's without cracks.
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mrjl
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Posts: 42
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Post by mrjl on Jul 9, 2018 10:09:12 GMT
Ha, ok, so I should just crack on then (if you can excuse the pun)?
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Post by devontiger on Jul 9, 2018 14:34:21 GMT
mrjl, thats a cracking idea.
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Post by downunderdave on Jul 9, 2018 21:30:04 GMT
OK Dave, can I just paint the oven then? I’m not bothered about the cracks if they’re just superficial. Or would you recommend repairing as you described, patching the render and more drying fires? The outer shell is really just a protective layer and keeps the weather out. Cracks in it allow water entry that you can do without. As they are they will also provide an exit for water vapour in the insulation space. My solution was to fabricate two terra cotta caps, the lower one not touching the pipe to both allow for expansion and provide a space for steam release. The upper one sits above it with the space between it and the pipe filled with high temp silicon. A simpler solution could be a conical shroud made from thin stainless sheet that covers the cracks.
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mrjl
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Posts: 42
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Post by mrjl on Mar 22, 2021 9:54:11 GMT
Long term update for my project... After a couple years of reliable use my oven's render has started to fall off. Even though it's been covered a hard winter with no use might be to blame, or just time doing its thing perhaps. Either way, it's started to come off. A friend suggested using chicken wire in the new render that I'm planning to put on. Is that a good idea? I'm trying to find someone locally who can do the rendering for me as I think a professional job might last longer and look better. A couple people I've spoken to won't do it though as they just do regular houses etc and wouldn't know where to start with a WFO. Money is tight at the moment too so I might just have to do it again myself, reluctantly. Also, any tips for hacking the remaining render off? The area around the big patch that has fallen off is surprisingly solid, with no give at all, so I'm worried hacking it off is going to pull some of the insulating layer underneath it which is quite crumbly.
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