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Post by pete123 on Jul 3, 2012 18:53:17 GMT
In total there are 5 full bags - so 500 Litres of vermiculite mixed 6 to one cement with a splash of plasticiser. I might have over done the patting down on the previous 4 bags - i.e. compressing it a fraction too much? The last bag though is very rice crispy like with minimal compression. The wooden posts are just to keep the tarpaulin overhead. Attachments:
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Post by pete123 on Jul 3, 2012 18:55:49 GMT
Side view. It's not completely round but I assume it can be corrected when the render goes on. Attachments:
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Post by pete123 on Jul 3, 2012 18:57:35 GMT
A close up of the top. Attachments:
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Post by pete123 on Jul 3, 2012 19:09:02 GMT
The other side. I'll leave it a week and then put on the render. 4 Sharp Sand - 1 Cement - Screwfix waterproofer - perhaps a touch of lime? Some questions? Is a week OK to leave the vermiculite to dry a bit? Is my mix appropriate for the render? Shall I do 2 layers of render? Or is it just as good to bung on a whole inch in one go? To make it rounder some areas will have more than an inch. I know Terry has posted on the subject of Render I'll do some searching. Looking Good! Attachments:
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Post by pete123 on Jul 3, 2012 19:23:06 GMT
Also a question for Turkey if you are reading?
What brand / make is the "clear silicone breathable waterproofer" you mentioned having in your shed?
Pete
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Post by bookemdanno on Jul 4, 2012 12:47:18 GMT
Very nice work!
Personally, i'd leave this stage as long as possible to dry out. Then fill the areas you need to create your near perfect dome shape. Then two half inch (ish) layers of render, with the first coat and filled areas scratched whilst "green" to create a key for subsequent over coats. Only adding waterproofer to the last coat of render. My Mix ratio would be... 5 to 6 sharp, 1 Lime, 1 Cement. If your sand is a bit coarse, you can "soften" it with up to 50% building sand. Not sure what others have done, but a quick view of some of the other builds should fix it in your mind. I've also been tempted to cut a Plywood section to become a sort of curved "darby" or former for the render. This can be set to a central pivot point and rotated around the dome whilst the final coat is still green. This cuts off the highs and highlights the lows. Then the final layer can be polished off.
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Post by pete123 on Jul 4, 2012 15:50:43 GMT
Thanks Danno, a previous post by Turkey said similar about leaving it for as long as possible before render.
I like the principal of the former for the outside dome. I'm not quite sure I have the skills to make it work effectively. I'll keep it in mind though.
Does anyone know why some people recommend only adding the water-proofer to the outer layer of render?
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cec
WFO Team Player
Posts: 160
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Post by cec on Jul 4, 2012 16:23:20 GMT
I put my waterproofed on the outside coat . I was talking to a bricky near my work and this how and what he told me ..
If the waterproof er is put on the 1st render coat then this is waterproofed , so for the 2nd layer of render to stick to the 1st layer it needs to absorb ( suck / stick ) to 1st layer . Following . But if it has waterproof er on its waterproof so it can't stick . But his mate said he always puts it on the 1st coat , See what the others think Anyway I did mine on the last coat then painted it with masonry paint aswell to give a bit more protection .
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Post by bookemdanno on Jul 5, 2012 12:15:16 GMT
Think of it this way...If you had a coat that kept the rain out, then would you wear another one, or a wetsuit underneath it?
I have my reservations about the ability for the water thats in the oven at the moment to get out once the Cement render and waterproofing layer is on.
Cement render will have its own level of water resistance anyway, and as there is so much water held within the Vermicrete at this point in your build you really don't want to do too much to seal it all in. The beliefs is...this internal water is what then gets transferred into steam, which then causes stress fractures in the outer layers if heated to quickly. If you are getting itchy cooking fingers, or have a deadline, get the oven dried out as much as possible first with small increasing fires over a week or so, to chase the water out. Very small to begin with. You have the Tarp, so it'll stop any rains spoiling the work.
I'd say, get it as dry as you can before Rendering, as at best, the outer layers will create a shell that slows the ability for drying out.
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Post by pete123 on Jul 5, 2012 12:42:22 GMT
Many thanks, I'll leave it a week before I start any fires. Most of the moisture will have gone from the fire brick as I've had a few fires prior to the insulation going on. The tarpaulin is ideal because it keeps the rain off & allows the breeze around it to dry slowley & naturally. The vermiculite however must have gallons of water in it still. The Screwfix water-proofer isn't quite what it says as it is described on the back as ""A liquid admixture designed for use in reducing water absorption and making cement less permeable..." Read more: ukwoodfiredovenforum.proboards.com/index.cgi?board=pompeiiovens&action=display&thread=296&page=16#ixzz1zkbYJxSYAlthough less permeable at letting water in must also mean less permeable letting water out. I'll leave it as long as poss before rendering. There's no real rush to get it done.
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Post by cannyfradock on Jul 5, 2012 18:27:45 GMT
Pete I've been told by tradesmen (renderer/plasterer) that a waterproof render consists of a scratch coat (first layer) of normal render with waterproofer additive, then a second layer of normal render. The first layer is heavily scratched ....... I start my curing fires (drying out fires) at the earliest opportunity. Slowly, slowly and as often as poss. Terry nb....click to enlarge photo to see "the scratch coat" Attachments:
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Post by pete123 on Jul 9, 2012 19:55:25 GMT
I've restarted my small fires. Only about an hour or so. I've tried my thermocouples out and they seem spot on. Brilliant actually. I only put them there for the picture - too long & they would melt! I also bought an IR thermometer as well ( on the right of the picture). Attachments:
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Post by pete123 on Jul 9, 2012 20:06:14 GMT
A close up. 107 for the top sensor & 38 degrees C for the bottom. When you point the IR gun at the spot where the lower sensor is it was reading about 55 degrees C. The top sensor is at a 90 degrees angle to the brick and obviously higher up. The bottom one is angled a bit more horizontally. Attachments:
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Post by pete123 on Jul 9, 2012 20:23:36 GMT
The Forno Bravo plans show the recommended curing fires as:-
Day 1 150 degrees C Maximum as long as poss 6 hrs minimum Day 2 as above Day 3 205 degrees C Day 4 232 degrees C Day 5 260 degrees C
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Post by tonyb on Jul 10, 2012 7:43:41 GMT
I'm always sceptical of specific temps such as these and not sure they are at all scientifically meaningful. Does anyone think it is really possible to meet such a specific temp using wood? And what happens if I don't reach / go above these temps?
I don't think you should take these temps literally but as an indication of small and gradually increasing fire size/temps.
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