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Post by lemonsouffle on Dec 10, 2012 17:20:08 GMT
Another pic of the fire Attachments:
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Post by cannyfradock on Dec 11, 2012 10:49:33 GMT
Love the pics........and the dome interior. Super job!!.
It looks like your'e well on the way to using it for Christmas.
Nice touch putting the flicker photo diary in your signature. Thanks for sharing.
I would love to see some pics of what you bake/cook in your oven.
Terry
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Post by turkey on Dec 11, 2012 14:45:45 GMT
very nice indeed, if you are using the KLWASC (I think its called) ready mix cement then you really need to get the whole structure up to a very high temp as its heat setting for its full strength I believe. So you need to cure the oven to make sure water has all evaporated and then once its safe you need to crank it up slightly and slowly and make sure the fires last long enough to get the outside of the oven well above 100 degrees, this will then ensure all of the cement it set well. carefully does it is an understatement It might be this final bake set might be best achieved when you have blanket insulation over it, that's dry and will aid keeping the heat in the dome, prior to any further wet layers.
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Post by lemonsouffle on Dec 11, 2012 23:05:15 GMT
Hi All
third day of curing fires today. I kept a fire going in the oven for about 6 hours today using mainly kindling purchased from the local garage - so not the most economical source but at least it was good dry wood. I made a small fire and topped it up to keep it burning all day. Eventually the exterior of the dome felt very warm to the touch, hotter at the top and cooler towards the bottom. Since the air temperature hardly rose above freezing all day it was quite an achievement to warm up the dome.
Turkey - we are using the KWALSC cement, it set really slowly which is why we could only complete 1 course of bricks a week and I realise it won't be fully set until the dome has been fired up to full temp. I plan to keep doing curing fires every day this week and then we might add the insulation next weekend. Does that seem sensible?
When the fires have been burning I haven't noticed any obvious moisture loss but there is a furry white deposit forming on the outside of the dome which I guess is the result of water and dissolved salts being driven out of the bricks. Has anyone else noticed this?
The curing fires are burning well with kindling but when I add larger pieces of firewood the fire seems to die down. Any suggestions on how to set a good fire?
Terry - I'll certainly post pictures once I start baking in the meantime here is a picture of a selection of bread that I baked in a conventional oven for my christmas party last year. There is a walnut bread, bay and onion loaf and a sourdough in this picture.
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Post by cannyfradock on Dec 12, 2012 12:54:14 GMT
LS Although I say that curing fires can start as soon as the dome is finished, the usual procedure is to still continue with the thermal layers. It's just as well you haven't put them on yet as I have a concern over the cement you used......don't be alarmed!! but you may just have to tweak the outside of the cement. If you have used purely KWALC cement, you may find the the thicker outside part of cement in the larger wedge shaped mortar is still soft. The KWALC is meant to be used for Liam's Vault ovens where the mortar joint is no more than 5mm thick. Have a look at the description of KWALC cement.. kilnlinings.co.uk/firebrick-cements-other-cement/cement-klw.a.s.c-firebrick-cement-heat-resistant-to-1600c If you have used JUST this cement......don't panic. Your dome wont fall down. What it might mean is that the outer part will never dry (push your finger into the mortar to see if it's still soft)....and you may have to scrape out the wet outside bit and re-fill with some homebrew. I don't want to put a spanner in the works at this stage of your build, but if this is the case, it's better to "fix it" now before putting on the thermal layers. As I said the dome will be fine...regardless. The pure nature of the structure of the dome means it can't go anywhere. Terry p.s....Just read Turkey's earlier post and don't want to contradict him as he's perfectly correct. I think Liam presumes that everybody cuts their fire-bricks so as the mortar joint is no larger than 5mm....which is often the case.
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Post by lemonsouffle on Dec 12, 2012 18:50:18 GMT
Hi Terry yes we are using the KLWASC, I spoke with Liam before I ordered it and he said that it should be ok. It was slow to set, especially on the first course when it was quite thick before we tapered the bricks on all sides but it has now set completely hard to the touch on the outside and I understand it will reach full strength when the oven is cured. We chose to use this rather than homebrew to make things simpler. No more fires today, I went christmas shopping. The insulation goes on at the weekend. How can you tell if the oven is cured before the first big fire? Any special signs to look for? Here is the bread picture that I promised in my last post. Attachments:
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Post by cannyfradock on Dec 12, 2012 20:56:55 GMT
Nice feedback....good news. I didn't wan't to be an alarmist but better I mentioned that than not mention anything at all. It sounds like you are A OK with the cement.
There is no given time for curing your oven. I recommend 2 weeks of slowly, slowly curing before firing your oven up hot enough for a pizza party. A lot depends on the moisture in the bricks...and how wide the mortar joints are. There is a lot of moisture to remove from the bricks and mortar before a full firing. Sometimes a longer curing process is needed if the dome is built and the insulation layers are put on at the same time. As you have already started the curing fires, then most of the moisture would have been released from the bricks and mortar.
As long as you take into account the reason for slowly curing (or drying) the oven is that too much moisture in the bricks and mortar will expand on a full firing and resulting in cracks. It sounds like you are well on schedule for an xmas pizza party.
You will know when the oven is hot enough to be used when the top of the dome turns from black to white. The white (or clean bricks) will start flowing down the sides of the dome. When the dome is completely white, then it's time to push the embers to the side or rear of the oven and ......start partying.
Normally a layer of thermal blanket is added, then a vermiculite layer. Try to get both done before fully firing. people are naturally impatient at this stage and some have fully fired the oven without finishing the thermal layers. As long as the dome is dry this works, but it means you have to put a lot more logs in to keep the massed heat in the dome.......at least try to have the thermal blanket in place before fully firing.
Terry
p.s......love the bread pics btw.
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Post by lemonsouffle on Dec 12, 2012 22:39:49 GMT
Hi Terry, thanks for the advice. We were worried about the thickness of the KLWASC at first but it is looking good. Will keep with the slow curing fires but when you are this close to the end it is hard to be patient.
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Post by lemonsouffle on Dec 18, 2012 16:19:00 GMT
Hi All,
a bit more progress, we have been doing curing fires for the last 10 days. A few hairline cracks appeared and were patched up at the weekend. We still don't have any insulation as it seemed logical to be able to see the bricks while we were at the curing stage.
Today I tried a bigger fire, it was soon roaring away and the top of the dome turned white inside, according to my IR thermometer the interior of the dome was approaching 300C and the exterior was 80-90C BUT more cracks have appeared. Mainly hairline cracks in the mortar but there is one scary crack near the top of the dome that is about 2mm wide and smoke was escaping from it so it obviously goes all the way through.
We obviously need to apply more mortar, any more advice?
Picture attached
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Post by lemonsouffle on Dec 18, 2012 16:23:29 GMT
Hi All,
a bit more progress, we have been doing curing fires for the last 10 days. A few hairline cracks appeared and were patched up at the weekend. We still don't have any insulation as it seemed logical to be able to see the bricks while we were at the curing stage.
Today I tried a bigger fire, it was soon roaring away and the top of the dome turned white inside, according to my IR thermometer the interior of the dome was approaching 300C and the exterior was 80-90C BUT more cracks have appeared. Mainly hairline cracks in the mortar but there is one scary crack near the top of the dome that is about 2mm wide and smoke was escaping from it so it obviously goes all the way through.
We obviously need to apply more mortar, any more advice?
Picture attached
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Post by lemonsouffle on Dec 18, 2012 16:30:34 GMT
That post didn't go very well,
Here is the picture.
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Post by lemonsouffle on Dec 18, 2012 18:59:29 GMT
another attempt at adding the picture. Attachments:
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Post by cannyfradock on Dec 18, 2012 21:55:43 GMT
LS
I expected to see a crack running vertical from top to bottom direction. I still think that the cracking is because you used fire-cement. You've done a fine job of the dome especially as you have cut angled or "trapazoid" bricks for a more even fit of the bricks. This means that even with cracking your dome is going nowhere. The pure nature of the construction means it CANNOT fail.
I could be very much wrong but even though it says that the KL fire-cement won't set above 5mm...... (and I think in places it must have been used greater than 5mm)......I think it may set due to the temperatures involved, but expansion and contraction of any refractory product before being cured will result in cracking.
I can only suggest what I would do under the same circumstances......any cracks that open up during a full firing will probably close to just show cracking when cold. I would buy some aluminium needles and mix them with a wet slurry of cement hydrated lime and sand at a ratio of 1;1;3......make this as wet as you like so the slurry penetrates deep into the cracks. With the addition of aluminium needles this will give the whole outside of the dome a reinforced layer protecting movement from the dome. It may take the appearance of a bald hedgehog but this will cure the cracking....maybe.
You have said that the outside fire-cement is dry so this is just my suggestion of a cure. I welcome........and invite contradiction to my solution from any members that have other ideas of their own which may give differing opinions to this situation.
Terry
afterthought.........make sure the mortar in the area that has cracked is fully set and not just formed a crust.
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Post by bookemdanno on Dec 19, 2012 13:28:32 GMT
Get your insulation on, finish the oven and in no time at all you'll forget about the cracks!! I have! As Terry said, your build has inherent mechanical properties which will not let you down. The smoke could have been steam from within the joint also.
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Post by turkey on Dec 27, 2012 18:58:35 GMT
I used homebrew and had cracks very similar to those, when heated things expand, even refractory bricks, that could just be thermal expansion. I did add a think Layer of homebrew round the complete dome to "seal" it but that had a few cracks also when dried.
I would keep with the heating and see if you get less out of the crack, in which case the cause was steam so just patch and continue.
if it stays the same then its just thermal movement and their is little to do but do a small slip layer and move on to the next layer . You could just regular lime mortar for the slip, or lime and cement together, if you have loads of high heat stuff you could use that but will be hard to get it to set really, as it will be assisting rather than structural I would go with the cheap regular materials (lime sand cement)
set or not the brick shapes are self supporting, and even wet not set its physically there aiding the dome "structure", looks great. If you did the lazy no brick cuts method it might be more of an issue , as it is I think its a Jon issue just one of those slight quarks all builds have :-)
either way that dome is not coming down and I would guess its pretty dry now so its thermally stable and could take a beating if you really stoked the fire, the insulation layers and final render will be very wet so you will need to keep with the slowly slowly to get those to dry, and as you have seen the further out the cooler it will be / harder to dry. Also more steam trying to force its way out so its really a case of long slow low heat to dry it out. Add insulation and the render sees very little heat but can trap a lot of water. I pushed my luck there and have lovely cracks in my final render to show for it, which means water ingress so more steam in the next firing no doubt so back to stage 1 for me in the "curing" but fires are fun so it's not all that bad ;-)
looks like you are doing a cracking job and the brick cuts look very impressive, its always a shame to have to cover the domes but it has to be done.
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