Part 8 - Fire me up!

I know I should have left this until next weekend, but being a fairly impatient kind a guy, well I couldn’t resist having a crack late morning Sunday with a short 2 hour window….

The fire was lit, and for the next hour smoked like buggery. Sydney in winter is not so bad - however I can see in the summer this is going to get interesting -  fires are quickly leapt on by the fire brigade on so I’m going to need to find a way to create a less smoky start-up. The long flue helped get the smoke up and away, which was great.

Once burning hot the outside surface remained cool for a long time. There I was thinking “wow great insulation” when the steam began to rise off the surface. The heat grew. At one point I could actually hear the water boiling inside the vermiculite, and for a while wondered if I might be picking up pieces of exploded oven from all over the neighborhood. Note to self: The insulation  mix definitely needs some time to dry - especially since Vermiculite is very absorbent and holds a lot of moisture.

Also I noticed the flue getting seriously hot and at one point a discoloration appeared on the galavised surface. I had gone for a double skinned gas flue thinking that this would work well. The discoloration turned out to be a result of the inner skin of the long extension piece. Melted. Blimey this thing generates some heat.

While the oven was heating through I prepped some dough and toppings for a very quick trial. Fortunately I had some home made tomato base in the freezer too. For the purposes of the test I made 2 pizzas in 12″ trays though in future I plan to drop the pizzas straight onto hot brick.

What a great sight to see my bubbling round of cheesiness against a glowing backdrop of embers. And the result: family and friends absolutely convinced that the last few months of pizza oven talk, might just have been worth it!

Seriously the hypothesis that wood-fired trumps everything is proven beyond doubt… if you’ve been thinking about building an oven - do it, do it, DO IT.

OK, so we ended up last weekend with an ugly looking part brick, part clay oven… yes definitely on the way to an oven. I went around the brickwork filling gaps with Hebel adhesive. I lit a small fire and watched the steam rising off the still damp clay. The flue extension went in nicely and took a lot of the smoke up and away. Initially I had thought this was way too long, but I think it’s going to be perfect.

This week’s part of the process began with some crack filling - yes a few more appeared in the drying.
I found Vermiculite from a Hydroponic supplier, see the pic above. It’s a super light substance and when mixed 6:1:1 with clay and cement forms a sloppy (and quite difficult to work) mix. The Vermiculite mix covered everything with an thick and even layer of insulation - aiming for around another 50mm thick. At this point the final shape of the oven emerged…I’m really quite happy with it.

The last stage will be a final coat on the oven exterior but for now we’re ready for a trial - leave it overnight and let’s fire it up!

Long weekend in Sydney and time to make some progress. First step was to rough out the shape of the oven, igloo-esque seemed to work best. The fire cement ran low and I skimped on this - which has caused some problems. This outline needs to be well cemented-in as the sand mould and working the clay in puts pressure on the sides and a few of the bricks became loose - not so much a problem if your oven is going to be static. A real problem for mobility though!

I built a mould for the door, allowing a lip or the door piece to fit in snugly - this was about 450 wide and 250 high. I weighted this down and then packed the oven space with filler (a few left over Hebel bricks and timber off-cuts). Then the sand mould was created and the flue roughly positioned. This flue is a double-skinned gas flue - it has an stainless interior and galvanised exterior. It’s actually a spacer on to which fits a much longer piece, again something I thought would suit the portability.

Then came the fun bit. My boys helped me mix a 2:1 sand clay mix. We cut the bristles off an old paintbush in order to get some natural fibre into the dry mix and then added a few trowels worth of cement. The whole mix squidged up really quickly when water was sparingly added into a very satisfying (and as it turns out, very throwable, mixture - as my 4 year old discovered).  It took about an hour to get 3 layers on the oven with a constant supply of cunningly fashioned patties. The door area took quite a bit of shaping and cajoling, its fun stuff to work with.

I left out the builder mix called for in the plan I’m following (see part 1). The clay I settled for is called ball clay and comes in 25KG bags costing $30 each - I bought three and have used less than one so far.

A few hours later and the clay started to harden up - it had cracked in two places - expected and easily remedied with more mix. One of these was on the door lip and I decided to lose the option for a tightly fitting door in favour of a more rounded opening (not sure I’m going to need a door as we’ll be cooking mainly pizza). Plus It’s so easy to work with I can aways add this later.

Also, in hindsight I think I should have created a bit more height in the outline, now that the sand has been removed I feel the space looks a bit on the tight side - but we’ll see. More pics to come.

A wet blustery day in Sydney today - kids soccer and rugby cancelled this morning which meant I had some time to get the clay pavers onto the Portable Pizza Oven base.

About 38 clay pavers in total, cut them using a hired wet saw. Cemented them to the Hebel layer using fireproof cement, a hideously expensive item at 25 bucks a pot - I used two, but really not convinced it’s needed - I wonder if mortar might have done the trick. Decided on a protruding  lip at the oven door end.

Next step is to rough out the actual oven shape. This is proving to be a conundrum. By necessity the design is narrower than I would have liked, which is why I made it a wee bit longer. Of course this is going to make for a bunker-like oven (I wanted to be able to get 2 pizzas in at once too).

Time for a bit more research…

Now that the stand is mobilised and complete, time to get ready for the ‘heat face’. I’m using a layer of Hebel brick - and onto this will go a low cost clay paver. For those who don’t know Hebel, its an extremely light and fire resistant building material. The roughly 900mm x 1200mm stand needed seven bricks.

Hebel can be cut super easily with any kind of saw and requires a special cement too. I made a bit of a pigs ear of this (made the cement a bit too watery), however a second skim this weekend sorted that out. I’ve decided to leave the Hebel exposed on the sides (budget is getting tight) and I’ll treat this in someway perhaps with the final pigment I’ll use on the oven exterior.

I spent a couple of hours this weekend shopping for the the next set of materials - clay pavers, builders sand, fire cement, even a double skinned gas flu (not sure if I’ll use this yet). But couldn’t find clay. Working on this.

Time to get started on the base.

The first stage is pretty simple using 100mm x 45mm treated pine timber. It comes in 3.6M lengths at least from from my local hardware shop (Bunnings Artarmon in North Sydney - great store worthy of many hours investment).

So far I’ve been through five lengths in total they’re $25 each. You’ll need three for this first stage. I got the store to cut it for me and then screwed it into this format using 70mm galvanised hex bit screws. Of course I hadn’t decided on the means of portability totally at this point, and so when I settled on the 450 mm diameter wheels I realised it was just too high. So you’ll see in the pics that I but the legs down by about 150mm.

Next step was to toughen up the lower part to handle the wheels and moving the beast around.

Check out that wheel! Definitely Lancaster Bomber material, or maybe a Mosquito.

…And here its is before the Hebel Brick layer.
At this point it really feels extremely sturdy. If it looks a little ‘bodged together’ that because it is. (Hey wait ’til you see the next stage, I never pretended to be a carpenter/DIY guy extraordinaire - believe me if I can do this, then you can).

Measurements? Hmm yes, I’ll supply all that stuff at the end in a wrap up. Main thing is we’re ready for the next layer.

This is my lizard mate, he’s a beauty - about 12cm long - shot him on one on my Pizza Oven Hebel Bricks… Hope he keeps those nasty Aussie spiders at bay. My 4 year old, got quite a shock on the cold day I took this shot, having told him not to touch. Of course when my back was turned he went for a good poke only to get the shock of his life when sluggish lizard sped off! Anyone know what sort he is?

Getting Mobile

OK, concept sorted, but how to make it mobile?

When finished the thing will weigh 200+ KG – not something that a simple BBQ stand will work for. Plus, when you think that the oven must be capable of being pushed over grass, up the side of a house with steep incline, onto a trailer and off at the other end… then you realise that you have a challenge!

At one point I seriously looked at building a trailer like one of these (image credit)…

But expense is an issue – a trailer would cost at least AU$6,000 – and wouldn’t fit behind my house anyway.

Sizewise I’ve settled on 900mm max wide and so made a bit more in the length to 1200mm.

The budget: I really don’t want to spend more that AU$600 all up (and this is proving to be a big challenge).

I’ve settled on a treated pine timber frame both for cost reasons and because I’m not a great metalworker. What wheels? When it came down to it large pneumatic castors seemed the most appropriate, and I ummed and aahhed on this for a while tossing up between axle-based wheels and castors.

Eventually a couple of calls to Castors and Industrial and I decided on a 45cm diameter pneumatic castor.

See right hand castor

Two fixed and two swivel - they worked out at about AU$80 each delivered - a painful blow…until they arrived. I’m reminded of the landing gear of a Lancaster Bomber.. and I’m convinced they’ll be the making of the oven.

Next… the frame.