nixie
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Posts: 144
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Post by nixie on Jun 25, 2013 8:46:49 GMT
Hi Terry, Thanks for the suggestions. I tried something similar to your slurry suggestion on Saturday (that is what the wide marks around the cracks are), however I didn't make much of it up and was used the base clay sand mix watered down so it didn't flow well. Nicely burnt my fingers trying to work it into the gaps. I've got some wood ready for a burn tonight so will get it warm and then try again. Just hope my wife doesn't catch me stealing play sand from out daughters sand pit . What I might try if that doesn't do it is to chase the cracks out a little (say half way through the dome), slurry the deeper bit then back fill with clay sand mix that's already as dry as I can get it. I'm not too disheartened (yet), it would have been nice to make one that didn't crack but I'm sure it'll work out in the end. After all there is still the insulation layer to go on which I understand also adds strength and can help close up cracks. I'm hoping that I can get a few more fires done this week so that I can use one of the weekend ones to cook something with. That I'm sure will remove any lingering despondency.
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nixie
WFO Team Player
Posts: 144
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Post by nixie on Jun 26, 2013 9:51:01 GMT
Had a burn last night and tried to fill the gaps with slurry, seemed to work ok at the time. The slurry turn some of the adjoining clay to paste too so hopefully I got a good bond. There is a very slight crack down the middle of some of the fixes this morning. Guess I'll have to wait and see till the next burn to see how well it actually work. I have burnt fingers tips now though !
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Post by spinal on Jun 26, 2013 12:10:47 GMT
You may need to repeat it a few times until your dome is "stressed" when cold. I.e. the clay is then under pressure when cold, but when heated it can expand without cracking
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nixie
WFO Team Player
Posts: 144
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Post by nixie on Jun 26, 2013 13:04:46 GMT
Thought that might be the case. As long as the gaps get smaller each time I'll be happy.
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Post by spinal on Jun 26, 2013 14:06:41 GMT
The only concern is that if it doesn't bond with the sides, you may end up causing the crack to get bigger... So it's a "cross your fingers" situation
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Post by mattfarmer on Jun 26, 2013 14:45:32 GMT
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Woody
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Post by Woody on Jun 26, 2013 20:10:09 GMT
Just asking as I have no idea ... Is this just a feature of using clay and therefore expected, or is this something that could be prevented by using a different mixture? or other ingredients like lime?
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Post by spinal on Jun 27, 2013 8:06:39 GMT
That's quite a crack!
I think it's partly a feature, but it can be minimised by letting the oven dry out slowly... fast drying and clay don't go well together.
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Woody
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Posts: 49
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Post by Woody on Jun 27, 2013 10:40:31 GMT
What about adding the second layer very soon after? Would that just hide the crack, or would it prevent the crack from occurring by keeping the inner layer protected? [ As i write this I'm thinking it maybe hard to tell if you can't see ... A bit like if a tree fell in a forest and nobody was there ... ]
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Post by spinal on Jun 27, 2013 10:44:05 GMT
Not sure...might be worth trying, going for a few weeks of firing then cutting it up to see
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Post by mattfarmer on Jun 27, 2013 10:59:05 GMT
I know, it scared the life out of me when I saw the crack, I thought the complete dome would cave in, but after filling it with some spare mix it is now rock solid. I took 6 weeks to slowly remove the sand former and used tealights to gradually dry out the inside of the dome. I think a lot of the cracking in clay ovens has to do with the speed of drying and also the ratio of sand to clay. I used 2 sand to 1 clay but may have been better with more sand. I will be building the insulation layer next weekend so i'm interested to see if that will suffer the same cracking.
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nixie
WFO Team Player
Posts: 144
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Post by nixie on Jun 27, 2013 11:11:41 GMT
I'm sure I went to hot too quick. Oh well. Its reassuring to see pictures that make my cracks look minor. At no point have I been able to see through the dome.
My clay was also quite damp I think,the last mix I made up was much dryer and harder to work so it could be that I need more sand in the mix.
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nixie
WFO Team Player
Posts: 144
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Post by nixie on Jul 1, 2013 15:35:10 GMT
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Post by cannyfradock on Jul 1, 2013 19:11:52 GMT
Nixie
A picture tells a thousand words.....Wow!!
Terry
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nixie
WFO Team Player
Posts: 144
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Post by nixie on Jul 1, 2013 19:52:38 GMT
Thanks Terry, so Glad it worked so well.
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