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salilah
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|  | Clay oven in Cambridge
« Thread Started on Sept 11, 2012, 1:06pm » | |
I'll add photos later when I have time to process them (and learn how to add them!)
My partner Chris and I went on a clay oven course at Wandlebury (great session, thanks Rupert!) and decided that this would be "a good thing to do" - we started about 3 weeks ago?
The first step was the base - four really solid posts concreted in, with very solid horizontal wood around the outside to give the structure. A wood base (18cm? or 15cm?) then sand then bricks... I'm still nervous that there is not enough of an insulation (air) gap underneath (2cm from the construction, plus a bit of digging)
The posts allowed for a roof - and after much debate and gently warmed discussion, we came up with a cantilevered model, which we tiled (dubiously) as we had some old tiles left over from the previous barn on site...
Sand form, then the first layer - we'd gone exploring down to a local stream for clay (none) but then found we had some clay left over from digging holes for some decking, so used that!
After leaving this for a day, we sawed off the entrance and left it again - for about a week. Large crack in the first layer (5mm wide) - so we decided to remove it and start again!
New start - bigger, as I was worried I wouldn't be able to get my bread loaves out of the old one! Now 60cm diameter, and 28cm high (but not very symmetrical - oh well).
Redid the first layer - seemed fine. Cut the entrance to 63% of height (not sure about this). Looked good!
We decided to build an arch entrance, so Chris built an amazing structure to give the form - it worked!
Second layer went on fine - we'd more or less run out of clay. We tried the suggestion from Rupert on the course to go up to the waste treatment site at Waterbeach and beg - well, no luck at all, nothing possible! On the way back, looked at the building site at Cambourne - and thought they wouldn't miss some lumps of very dry nasty brown stuff (!). This worked well, and we have now put the second layer on...
Slight challenge now, in that I can light a small fire in the entrance fine - but pushing it back means that it goes blue then goes out! Does this mean that the entrance is not high enough??? Any advice appreciated!!
S
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faz
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| | Re: Clay oven in Cambridge
« Reply #1 on Sept 11, 2012, 3:12pm » | |
Congrats on getting to a stage where you can light fires 
With regards to the blue flames, it sounds like your fire is not getting enough air to it. I see from your other post about cracks that you haven't removed all the sand from your entrance. I am not sure how much is left in the entrance, but if there is quite a lot then this will impede airflow and will probably cause your fire to go out.
If you post a picture it would be very useful.
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800degreedan
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| | Re: Clay oven in Cambridge
« Reply #2 on Sept 11, 2012, 3:25pm » | |
i agree soem pictures woudl tell a lot. if thwrs still sand inside yes airflow will be restricted, the magic number i recall is 63% , the door height should be 63% of the total height of the dome inside.
good luck look forward to pictures
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spinal
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| | Re: Clay oven in Cambridge
« Reply #3 on Sept 11, 2012, 4:06pm » | |
A blue flame is an oxidising flame... which is a little weird as it would suggest an excess of oxygen.
Could that be due to water/moisture in the oven? Can water (H20) cause an oxydising flame?
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dougclay
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| | Re: Clay oven in Cambridge
« Reply #4 on Sept 11, 2012, 7:49pm » | |
it will just be too damp for the fire. I lit tealight candles to gently warm the dome from within. on the outside the problem was the opposite, keeping the sun off to stop it drying too fast...
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spinal
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| | Re: Clay oven in Cambridge
« Reply #5 on Sept 11, 2012, 8:14pm » | |
Sun?! Are you sure you're in the UK? 
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dougclay
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| | Re: Clay oven in Cambridge
« Reply #6 on Sept 11, 2012, 8:26pm » | |
We built the oven last year in May, during the long heatwave.
it came as quite a shock when it finally rained and we suddenly had to worry about finding a shelter 
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salilah
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| | Re: Clay oven in Cambridge
« Reply #7 on Sept 12, 2012, 9:55am » | |
OK this is the base - posts are concreted in (lightly) and the wood on the sides firmly attached (timberlok I think) - we dug the soil away but I'm still not sure if there will be enough of an air gap for insulation
PS I only seem to be able to add one picture at a time this way - any suggestions of how i put them into the message??
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salilah
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| | Re: Clay oven in Cambridge
« Reply #8 on Sept 12, 2012, 9:58am » | |
This is the roof - you'll see we had shorter uprights at the back to give the angle, and it is cantilevered out to give a bit of a shelter in case of rain 
Quite a solid roof - too much in my view! - though we decided to tile it so it needed to be pretty strong. More debate about how to get this to work than any of the rest of the build!
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salilah
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| | Re: Clay oven in Cambridge
« Reply #9 on Sept 12, 2012, 9:59am » | |
Another one of the roof - it's quite a cramped space, you have to negotiate between the roof and the tree behind - painful!
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salilah
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| | Re: Clay oven in Cambridge
« Reply #10 on Sept 12, 2012, 10:00am » | |
More roof - showing the battens for hanging the tiles off...
We did have to re-do one or two - poor measuring!
Also - we cut them a bit short (getting 2 battens out of each bit of wood) and this meant that some tiles are not that solidly anchored - lesson learned, make battens full length!
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salilah
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| | Re: Clay oven in Cambridge
« Reply #11 on Sept 12, 2012, 10:02am » | |
This is the first layer (first time pre-crack)
Also shows the floor - just ordinary brick on top of a thick layer of sand. I did the bricks, then removed them so we could flatten and smooth the sand, then redid the bricks (much better). Filling in the corners with half-bricks and the edges with some "slips" (is that the right word?)
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salilah
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| | Re: Clay oven in Cambridge
« Reply #12 on Sept 12, 2012, 10:03am » | |
Sorry - pictures of the crack are on the camera not the card!
This is after the crack and rebuild - first layer - bigger by about 10cm diameter (so it is now 600 diameter and 280mm height inside)
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salilah
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| | Re: Clay oven in Cambridge
« Reply #13 on Sept 12, 2012, 10:06am » | |
After I'd seen a few pics here, I suggested that we should have a brick arch rather than the clay arch we were taught about on the course...
This is the shape (former?) for the arch - cut from the off-bits of wood from the roof I think, or from the base - shaped not to a perfect curve, but matching the somewhat unbalanced arch we cut in the clay!
Covered this with hardboard nailed on (screwed at the end so it would fit) - fiddly as hardboard really doesn't like this much of a bend!
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salilah
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| | Re: Clay oven in Cambridge
« Reply #14 on Sept 12, 2012, 10:07am » | |
Here is the arch in place, and the second layer of clay (much more yellowy than the first garden clay, this is from a huge building site)
The chimney is a bit of plastic held up on bricks in the entrance way
That's the last of the current photos - more to come when we do the insulation layer next - possibly next weekend!
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