Another UK oven started

[Carl]

Re: Another UK oven started

Time to start finishing off the oven walls, so I'm using more of the AAC (Thermalite) blocks. I bought these very cheap because they're all damaged (corners chipped off, some snapped in half), but I can still work them into the structure.



I'm having a 6" loose fill of vermiculite around the dome (minimum - this is at the base, and higher up there will probably be several feet worth) then the 4" thick outer wall of AAC block. I'll render over the outside surface when I'm done.



Getting closer to finishing now - must have another fire at the weekend...

[mmmhumous]

Re: Another UK oven started

I love the Temperature display it's fantastic!

[Carl]

Re: Another UK oven started

Too much building, not enough posting...

Well, I finished off the walls with insulating blocks, using the cheap damaged ones I bought. This made the front look like a patchwork quilt, but no matter, it'll all be hidden soon.



I rendered the back of the oven with a lime/cement/sharp sand mix - this bit won't be seen either when it's finished.



I decided to cover the front of the oven with flint block walling, since I got this large pile of flints free from my own garden. It's a traditional building style round here - the chalky soil is full of flints, and many of the old cottages round here use these in the walls in just this way.



I used a 1:1:4 cement:lime:grit sand mix to mortar the flints in, using screws in the thermalite blocks to bond the mortar to blocks.

[Carl]

Re: Another UK oven started

The flint block wall was fiddly, but after about three days of work I ended up with this:







Total cost was pretty minimal, thanks to the availability of the flints. I'm pleased with this look, and it'll look nicer still when I clean the surfaces of the split flints off.

I've added a 'costs' section to my blog - and so far my net cost on this build has been around ?200, thanks to freecycle, ebay and generous neighbours.

[gjbingham]

Re: Another UK oven started

Carl. Simply outstanding. I loved watching your build. It turned out very very nice. Congrats! What does your wife and family think now????

[Carl]

Re: Another UK oven started

Wife and family are now excited, waiting for the first food! The oven's still very damp though, due to all the mortar and render used. I'm having a series of small fires first before I start cooking to dry it all out first.

Now I need to build a path so everyone can get to it...

[Wlodek]

Re: Another UK oven started

I then filled all of the gaps round the oven entry arch with an insulating mix (my own recipe: 5 parts vermiculite, 2 parts fireclay, 1/2 part Portland, 1 part sodium silicate). This was a very sticky mix that set hard within a couple of hours.
...

Carl,
Are these proportions by weight or by volume?
Cheers,
W.

[Carl]

Re: Another UK oven started

Wlodek

All these proportions are by volume - by measuring, usually in a plastic tub because they're usually to hand in the garage. The sodium silicate (waterglass) is supplied as a liquid - same sort of consistency as maple syrup. The supplier I used for it is listed on my blog - the name escapes me right now.

My insulation mix seems to be holding up fine - just had the oven up to 450C last night, trying to dry the structure out. I tried it without the fireclay and it wasn't sticky or cohesive enough for my liking.

[Wlodek]

Re: Another UK oven started

I know you have heard this here a few times, but I'll add my little voice to the choir of admirers of your ideas, your resolve and of the result. Looks great and I am sure it will work great too.

W.

[asudavew]

Re: Another UK oven started

Excellent.

It turned out very nice.

Congrats!

Enjoy your pizza!

Dave

[Carl]

Re: Another UK oven started

Thanks everyone for you kind comments. I'd like to thank everyone on here who has provided advice to help me get this far.

I had a longer fire on Tuesday this week, and used my 6 thermocouples to keep track of what was happening. I've attached the graphs below.

The oven was still very damp, and steamed after the first hour - I think this was water in the vermiculite, thanks to all the mortar and render I used to finish it off. No damage though.

The 'below hearth insulation" line is the one underneath my AAC (thermalite) block. It seems to work well as an insulator - never went more than ~25 degrees above ambient, even as the oven cooled over the 24h. I should add that all this is without a door on the oven...

[Frances]

Re: Another UK oven started

Cool heat graphs, looks good. I'm thinking the heat retention will improve as the oven dries out more. And with a door of course.

Its been really fun watching your build. I loved the way you built your stand when I saw it just as I was starting out on my oven... and its just got better and better since then

[Carl]

Re: Another UK oven started

Thanks Frances for the kind words - I've really enjoyed the build. Must build a door this weekend... The insulation (loose vermiculite) got damp after I mortared all the flints in - it was steaming during this fire. Hopefully the heat retention will get better and better with more fires.

[sarah h]

Re: Another UK oven started

I was following your progress earlier on, then lost track for a while...
I caught up again this morning and just want to say well done - your oven looks great! I love the round shape and your stonework.
Happy baking!

Sarah

[Carl]

Re: Another UK oven started

Had a longer fire last weekend (still drying the oven out - the flint & mortar introduced load of water into the thermalite blocks) so I had more chance to watch the oven cool down. Still no door, but hope to build one next few days...

I've added the graphs again below if anyone's interested - one degrees C, one in degrees F, depending on your preference...

I stopped adding wood after 1 1/4 hours (tea break) then added more wood until 4 hours, after which I left the whole thing to cool down. Interesting to see how variable the surface temperature of the dome is, and how it drops very quickly once the fire goes out. You can really see how all the heat is locked up in the core of the dome - the 2" thick probe remained hottest all the way through the cool down.