Another UK oven started

[james]

Re: Another UK oven started

Although the dome seems bone dry, I'm now giving it another week with the 500W halogen before playing with fire. Better too dry, than not dry enough...

Hey Carl,

Great work. Another week of 500W, then a long, low and slow curing. There is an important transition period where you go hotter than a space warmer, but never let your oven to above 350?F. That will slowly bake the moisture out of your oven without stressing it. With your design, try to shoot for a series of extended days at 300?F-350?F. It's harder to do than it sounds. You have to build a successful, but low fire -- without letting it die out, or get too hot. :-)

Way to go.
James

[Frances]

Re: Another UK oven started

Very cool oven! I really look forward to hearing how the fires go...

[Carl]

Re: Another UK oven started

Thanks everyone - I'm itching to have a fire in it, but am fighting my urges. It's not easy...

James - Thanks for the advice - I'll try and use the thermocouples when I'm doing the curing fires to keep the temp below 350F.

[james]

Re: Another UK oven started

Carl,

Where are your thermocouples? If they are set back in the dome and floor, the inside of your oven will reach 350?F on the inside, and the outer reaches of the oven will still be room temperature. Alternatively, if your thermocouples are 3" away from the inside of the oven, and they reach 350?F, the inside of your oven will be really hot -- maybe 700?F+.

You can leave your hand inside a 350?F oven for a pretty long time. Very scientific. :-)
James

[Carl]

Re: Another UK oven started

Hmm, now where did I put those thermocouples. Off the top of my head (typically for me, it's written on a lump of wood next to the oven...) I think I think I've got 6:

- about 1/2" from the inside of the dome, about half way up on the side
- 2" into the dome (i.e. in the middle of the clay), about half way up
- on the outside of the dome , covered with about 1/4" clay to hold it there
- 1 " from the surface of the centre firebrick in the hearth
- under the insulating AAC block
- in the wall of the outer oven, near the door (under the corner of the entry)

I might have noted it on the blog... You can see the wires coming out of the dome in places.

The arm test sounds good enough - I shall just try and keep a really small fire going for a day to start. But not yet! :-)

[TBM66]

Re: Another UK oven started

Being a newbie I hesitate to make any suggestions.....but here it is. I think it may be easier to keep a couple of charcoal brickettes going than wood.

A tin can with holes around the bottom of outside wall of the can for draught would do the trick. use a bit of metal over the mouth to control tempurature

Just a thot

[gjbingham]

Re: Another UK oven started

Written on a block of wood. A man after my own heart. You probably burned that piece already.

Nice take on the pizza oven Carl. You certainly made it your own.

[Carl]

Re: Another UK oven started

Well, it's just had another 3 weeks with 500W halogen to dry, thanks to not getting time to work on it... No more cracks, so good news.

I filled the gap between the back of the chimney and the dome with vermiculite concrete - notice that the centre of the oven dome has got pretty hot with the halogen light and has gone very pale (no cracks, but far too hot to touch!).



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.



This mix is the flecked gray stuff you can see in the picture above. This was great stuff for filling all those awkward gaps - just mould a ball of it and shove it in.



I also used this mix to smooth off the transition between the rectangular brick chimney and the round chimney flue:



This gets rid of lots of sharp edges and corners - hopefully the smoke will want to go upwards even more now...

[Carl]

Re: Another UK oven started

The whole gap filling exercise took about an hour, and I'm pretty pleased with the finished look. I'd been wondering for ages how I was going to sort this bit out...

[Carl]

Re: Another UK oven started

Update: a day later and my insulation mix appears dry. It's dried to a colour similar to the mortar, and feels spongy like cork, yet solid. It's got some tiny hairline cracks in the bit above the oven entry - I'm guessing this bit dried too quickly due to the heat from the halogen light. The rest seems to dried well with no cracks.

I will leave it another day while I build my thermometer set up, then I'm going to start playing with fire....

[Carl]

Re: Another UK oven started

Hooray - found my extensive thermocouple placement notes...



... so decided to install the thermometer today. I'm using a PID temperature controller (close as I'll get to pyrometer on my budget) from Auberins - ?20 for the thermometer module, plus ?4 a go for thermocouples rated to 1000C. I also picked up a rotary thermocouple selector off ebay for ?5, so this lets me select where I read from.



So this is telling me it's 42C in the dome (thermocouple placed just sticking out of the surface - number 1), while outside in the walls...



... it's 11C. Not a bad setup for the money, and closes off that little brick hole on the front of the oven that everyone keeps asking me about ('is that where you make the fire'?)

[gjbingham]

Re: Another UK oven started

Ha! I love it Carl! Looks like science lab!

Great job on the oven. Is the family still shaking their heads and muttering behind your back now??? I bet they're starting to believe in you a bit more.

[Acoma]

Re: Another UK oven started

It's Cure time Wow, like the Olympic torch, I now pas it to you Carl What fun it will be.

[Carl]

Re: Another UK oven started

Thanks Acoma - curing torch received . Tonight was the first fire - a small one, with a couple of handfulls of wood scraps. It burned for about an hour and a half it total before I left the embers to cool.



These pictures were taken after about an hour - at this point the thermocouple inside the dome was reading 230C, the one 1 inch into the dome was reading 180C, and hearth one about 70-80C (again, 1 inch inside the brick - no doubt the surface was much hotter). I had some small cracks on the outside of the dome at the back - but only hairline (nothing on the inside), and no smoke leaked out. I'll have a proper look at these tomorrow - I don't think they'll be a problem. I'll keep doing these small fires to dry it out over the next week or so.



I'm really pleased with the chimney - the smoke went straight up - nothing out the front arch at all.

[Carl]

Re: Another UK oven started

The day after the fire I checked the cracks - and they'd gone! Well, they'd closed back up to being tiny hairline ones, from being big enough that you could just get a fingernail in them.

There's no sign of the cracks on the inside, but interestingly the outside cracks appear to match up with the 'courses' of clay blobs that are visible inside the dome. I guess this is just the weakest part of the dome, so it cracks here. They don't seem to be a problem, so I shall leave them right now. More small fires on the way...