New 36" Pompeii in Bondi

[Wozza]

So to the curing, which I started last Saturday after I fixed the ceramic rope:

Day 1

Started at 10:00am. Daughter and grandson were around, so we got him to (very carefully) light the first fire. Just a sheet of newspaper and some kindling so that he could say he did the very first one.

Then it was fire up some charcoal beads on the barbie and transfer them to a grille sitting about 50mm off the floor when they were burning nicely. Fire dead centre of oven. Occasionally topped up with some lump charcoal during the next few hours (ran out of beads). Oven temp showed 65 degrees (temp gauge about $8 from Victoria’s Kitchen). Back wall and top hovering around 100. Outside top of dome felt warm at 35. Inside top got up to 130 at one point. And around 4:30pm was close to 150. Started using some very thin pieces of wood. About 1/2 finger width. Finished at 7:00pm. Temp on the top of the dome got up to 180. Oven temp was 80 degrees. Blocked the entrance with some random pieces of Hebel and that was it.

Day 2

Start again at 10:00am. Fire left of centre. Condensation on underside of tarp when I took it off. Used the last of the lump charcoal and then went off to buy another 4 bags of beads. Kept it ticking over at oven temp of 85 degrees and let it creep up to 100. Kept adding small sticks every now and then to keep some flames going. Sticks about finger size. Smoked a lot trying to get the wood to ignite from the heat of the charcoal.

Beer o'clock and I finished working in the garden and spent the next couple of hours giving my oven some personal attention. Used wood continuously from then on and hardly any smoke if you keep the flames going. Quite a pleasant way to spend a cool evening...a decent beer and staring into the flames. Which were reaching the top of dome and the temp there kept creeping up and just before I finished it reached 250 and the oven temp was 110. The dome is sooting down to the third course. No cracks, buts early days yet. Cut some Hebel blocks to make a better fitting door and called it a day.

I noticed there is a direct correlation between the number of beers consumed and the urge to put more wood on the fire. I also noticed that if you leave all the sticks you've chopped too near the fire to warm up, they will, when you are otherwise engaged (getting another beer), spontaneously burst into flames and you lose arm hair trying to get them out.

Day 3

Condensation on the tarp when I took it off. And the oven had dropped from 110 to 65.

Threw in some heat beads about 9:30am, fire on right of centre, and just kept it ticking over at low heat while I did some work in the garden until 3:30pm. Then added some finger sized pieces of wood and we're up to 110 within 30 minutes. Some slightly thicker wood and then on to oven temp at 125 and mid wall about 250. Top of dome around 300. Outside top is ambient temperature. Can't feel any warmth.

Up to 145 after another hour and a half. Side wall near fire is still 250 and top of dome risen to 350. Try to hold it there for another hour and a half.

And finish with the oven at 145 with sidewall closer to 300 and top around 380. There was one point where I was a little generous with the wood and the oven got to 160 and the top of the dome went over 400. I put a couple of Hebel blocks cut to suit in the doorway and stuck around for a few minutes to see if the fire went out. After a couple of minutes I had a look and the temp had gone to 180. Another few minutes and it reached 200. Seemed to want to stay there so I left it to itself.

Obviously a lot of heat disappears out of the door when you're firing up normally, but if you close up with an insulated door, that temp will still keep heading north for a while. Presumably until the fire goes out due to lack of oxygen. Checked it again a half an hour later and the fire was out and temp at 185.

One piccie shows the oven at 145 and the other shows the approximate size of wood for each day so far. The round piece is some bamboo that came from an old bamboo and rattan sofa that we’ve had for many years and was finally cut up a couple of days ago. The tarp had condensation on the underside in the morning and the oven temp was 110.

Anyway, quite happy so far. Gone from 80 to 110 to 145 (and temporarily up to 160). And those firings are about 9 hours each, so 27 hours total and no cracks so far.

Day 4

Well, do we call it a crack or is it more an inbuilt expansion joint? Noticed it on the right on the oven going vertical between 3 courses (3, 4 and 5). It’s at a point where the joints on those three courses line up reasonably closely. Took a piccie, but it’s too small to see, so press on.

This was Evening 4 as it was back earning a living today and I didn’t start until 6:00pm.

Put a few charcoal beads in and then started with some small wood and worked up to pretty much the same sizes as I was using on Day 3. Fire dead centre on a grille supported by Hebel blocks. Slowly crept up to 185 and kept it there for an hour and a half. Walls about 230 and roof around 290. Had to break for dinner so I closed up the entrance with my temporary Hebel door and left it for ? hour. Then relit some sticks and we were back to 185. Outside ot dome still ambient temp (around 14 degrees).

I was going to close it down at 10:00pm so put the lower door block in place (which covers about the bottom 2/3rds of the door) and watched the fire for a few minutes. The flames died down slowly but the temperature went up to 215. Quite a slow burn but the heat was being kept in. I experimented with blocking off the top 1/3 of the entrance with some wood and found I could control the burn quite well, keeping the flames low but the temperature up. Built the fire up with a few more sticks and kept it ticking over slowly for another hour and then let it die down to 185 again and closed up.

I think that I’ll try this tomorrow night – get a good fire going, then ‘throttle back’ to see if I can get to maybe 250 without having to build up a roaring fire.

Incidentally, the centre part of the dome started getting a little white-flecked at one point. I guess this was a little of the soot starting to burn off. And I checked it in the morning and there was condensation on the tarp again and the oven temp was 130.

Starting to think that if I get another couple of 3 to– 4 hours burns this week and then three 8 –to 9 hour burns on Saturday, Sunday and Monday, then I might be in a position to render this thing the weekend after.

Is there a God of Pizza ovens to which I can offer a sacrifice of something to ensure no more cracks?

[david s]

Your oven will still be purging itself of moisture after the fire has died but while it is still hot. So don't tarp it unless it looks like rain. A tarp will keep moisture out, but will also hold moisture in.

[Wozza]

Started Day 5 earlier, but then I noticed something that worries me a little. The neighbours to the back of me and to both sides have palms. The ones at the back are quite nice as they frame the wooden slats I've put on the back wall. However...

I noticed this evening, after I lit the fire (and for whatever reason, it was a little smoky), that the tips of all the fronds on all three properties are turning brown. Now I'm no horticulturist, but I'm putting two and two together and thinking it's been the smoke over the last few days that's causing this. And that could be because I've been using wood mostly from an old ceiling I dismantled a few months ago. It was part of the original house so is almost 90 years old, bone dry, reasonably thick and burns well. Why wouldn't I use it...except that maybe it's been treated in some way and I'm poisoning the plants. I also used a few pine offcuts a couple of days ago that I know was treated.

So I let the fire burn out and I'm wondering how to proceed. I have a lot of wood under the deck and about a third of it is offcuts from here and there and I have no idea if it's treated or not. The other two thirds is wood I have collected whenever a tree has been cut down locally. That stuff will be good to go and there's a lot of work involved in cutting it to size, but the rest..? I think I'm going to have to get rid of it just in case and hope to hell the palms are only temporarily under the weather.

[Wozza]

OK…I decided to bin all the offcuts of wood that I’ve got. I would burn it in a high temp wood fired heater but a pizza oven is a different matter. So I bagged most of it on the weekend and put it outside the house with a large sign saying ‘Free firewood’. It was gone within the hour. Free heat for someone. So what I have left is effectively bits of tree, most of which I have had under cover for maybe three years or more.

I dug out some of the smaller bits and it was out with the axe and I split enough for 2 or three fires. And it was on to the official…

Day 5

A Saturday and a pretty straight forward fire. Didn’t bother with charcoal this time. Went straight to kindling and then built it up to around 250 and kept it there for a couple of hours. Walls were about 325 and underside of dome close to 400. Towards the end I let it creep up to 300 with the walls around 350 and the dome just over 400. Total time about 4 hours. I let the fire burn down and put some logs in to really dry out and closed up on with my Hebel block door.

Day 6

This was 2 days after the last fire (Sunday was intermittent rain), so it had a day and a half soaking in the heat from Day 5. Started with kindling again and built up to close to 320 after an hour and a half. Floor was 325, walls around 420 and dome at 470. And then…glory be, the dome started clearing! Nice to see. Even went in to tell SWMBO and was met, not unnaturally, with a blank stare. Bit more wood and let it climb past the highest mark on my cheap and cheerful temp gauge but it must have been around 325. Floor was then at 350, walls at 440 and dome at 470. I think we’re ready for pizza…

After total of 2 ? hours I let the fire die down to around 300 and put on the door.

That was the good news. Bad news was…another small crack. Adjacent the last one but no big deal. Could just make it out as the wall was clearing. I’m not going to worry about it. I would have preferred no cracks at all and I think I’ve been reasonably cautious. But thinking about how this thing is put together, it’s made specifically so that there is no room between bricks to give it structural strength and then we hit the thing with temps off the scale and however carefully you cure the damn thing, a few dozen bricks are going to expand – no question about it. In fact, if you wanted to build a brick structure that was almost guaranteed to have a few cracks, you’d build a brick dome and then light a fire inside and take the brick temperature north of 400 degrees.

The tarp still had condensation on it this morning. I would have expected it to be pretty dry by now. And I’ll check the temp tonight after 24 hours to see how well the heat holds. I think it’ll be OK as the outside of the dome is hardly getting a degree or two over ambient.

I don't think I'll bother with any fires during the week. But Saturday I'll take it back to clearing temp (I assume it smokes back up as the temperature drops) and it's pizza for dinner, plus a few beers, a decent red and the finals of the footy.

[Wozza]

Forgot the piccie. This is just as the dome was clearing.

And one thing I noticed...I thought it might have been the piece of wood I'd just thrown on, but I seemed to get some black smoke at one point. And then I noticed the dome clearing. Is it that the soot burning off creates a reasonable amount of black smoke?

[Steady]

It's a good feeling to see the dome clear - the daughter that has been helping with my build got just as exited as I did when our dome cleared but the rest of the family just had the blank stare you experienced when we told them.........

[david s]

Forgot the piccie. This is just as the dome was clearing.

And one thing I noticed...I thought it might have been the piece of wood I'd just thrown on, but I seemed to get some black smoke at one point. And then I noticed the dome clearing. Is it that the soot burning off creates a reasonable amount of black smoke?

The black smoke would be from the extra bit of wood you threw in. Because the wood is still cold the smoke it produces is not hot enough to burn away. I often pre heat bits of wood in the entry so when thrown in they ignite almost immediately and burn much better.

[Wozza]

Those couple of small cracks were pissing me off and there was a loose piece of mortar on one of them, so I dug out the last of the high temp mortar and managed to reach in far enough to get some in between the bricks. Left it all day and went off for a couple of beers with a mate in the arvo.

The family got home before me and were keen to get things started so when I got in, the fire was going and we all sat around and talked for a couple of hours as the temperature went up to 300 C and then over as the dome cleared. The floor was at around 370 according to the infra-red, so it was pizza time.

We kept it simple. Made the pizzas on wooden peels I?d bought for $15 a pop at Victoria?s Kitchen and used them to slide them into the oven. Then it was the long handled metal peel to move it further in and turn as required. And everyone thought it was pretty good for a first effort. We made 6 all up. A few different toppings ? aubergine, potato, different types of cheese, garlic and some salami. Kept the fire built up but we lost a little heat on the floor so I dragged some hot coals over the cooking area for a few minutes.

I think what would be beneficial would be a stack of relatively small sticks to keep the flames licking over the dome as the pizzas are cooking. I tried lifting them up to the top of the dome for a few seconds on occasion and that seemed to work well. Timed a few of them and they were all around the two minute mark although one I took out at 90 seconds was pretty much done as well. All in all, quite happy.

There was a discussion later as to what the temp was going to be the following morning. I thought mid 100?s which was the highest guess and it came in at 160. Pleased with that although I think as it dries out further it may go up. In any case, I threw in some wood in the late afternoon on Sunday to get the temp back up to low 200?s and put in a tray of lamb shoulder cut into chunks, potatoes, lemons, garlic and onions with a fair amount of rosemary and oregano with a cup of water to keep it moist.

Four hours later and there was a pretty good Greek dish for dinner. Rock and roll?

[cobblerdave]

G'day
Great to hear things are going well and you've enjoyed your first pizza!
The Sticks are a must to keep the heat radiating from the dome, especially since is 1/2 round. I keep 1/2 doz at any one time to one side in the entrance. The radiated heat will mean they will burst into flame straight away as soon as they hit the coals.
Congrats again
Regards dave

[UtahBeehiver]

I think if someone says they don't have any cracks, on their oven any where, they are either a politician, used car salesman or a liar or both. I always use small wood to once the coals are pushed to the side for the same reason Dave says but also, a lot of the time I am cooking pizza in the evening and the light from the fire helps me see what is going on inside the dome. Congrats on starting the cooking adventure. Also dragging the coals over like you say regen the floor heat but also cleans the floor surface of oils and spilled food. That is last thing I do and the end of the night and I have a self cleaning oven.

[david s]

" a politician, used car salesman or a liar or both"

It would be tempting and easy to add more to that list.

[Wozza]

Well, I've bent the truth a few times in the last few months.

No, dear, it won't be very big.
Nah, just a few hundred bucks, if that.
Mmm, probably take a few weeks.
Of course I don't need an infra red gun.
We don't need more than one wooden peel.
Yes, paintintg the bedrooms is still the priority.
I doubt if I'll need to go to Bunnies this weekend.
No, there probably won't be more than a dozen or so people coming to the Grand Opening.
I'll handle it all, you won't have to do anything.
And no, I'll only have a couple of beers.

She never believed any of it...

[UtahBeehiver]

Smart SWMBO......

[Wozza]

And then decided it was time to render the dome. I think that any residual heat in the dome will cause some condensation on the underside of the tarp and I don?t think it?s necessarily water being expelled at this stage. It will, at some point, just be the normal condensation you get on any flat surface when you get a slight temperature difference. Relatively warm on the underside of the tarp, relatively cool on the outside and you are guaranteed condensation.

I felt it had had enough time to dry out enough ? we?re talking well over 40 hour?s worth of active heat (actually burning wood) and I don?t know how many hours of letting that heat soak into the dome with the oven locked up with my cheap and cheerful Hebel block door.

So I mixed the render at 4:1:1 (sand, cement and lime) and skimmed the whole thing in about 2 hours. I?d bought a 25mm brass pipe fitting/nipple and a screw cap for about five bucks (at Bunnies ? where else?). It?s about 75mm long and I dug out a little of the vermiculite until I was down to the blanket and rendered the thing in at top dead centre. If there is any residual moisture in there now, or if some works its way through at some point, then we have a relief point.

No time to put a second coat on it before the grandson?s pizza party on Sunday so I?ll have to leave it a little rough until next week. Looks kinda rustic anyway, although SWMBO thought it looked better with the vermiculite finish. Go figure?

And then I?ve discovered a nice looking finish for the whole thing ? Rockcote. There?s an outlet that sells it down in Tempe so I may take a spin down there at some point and see if it?s what I need. The web site says you can get a finish that?s like sandstone, which is what I wanted. And you can colour it as you would paint. It?s like a very thick paint or a very thin render. It?s water resistant in its own right but I think they also sell a finish that you can apply which will make it more so. It might be OK to use that finish on the blockwork walls as well (which I rendered a couple of weeks back).

Until I get that done I?ll keep it covered with a tarp. Then I need to make a decision on the finish to the hearth. Some sort of tiles I think. And I still like the idea of a mosaic dragon on the side but not sure how that would tie in with the Rockcote.