Thoughs with small WFO mods?

[dariusk]

Hey there

While I am accumulating the material for my larger brick oven, which the build will likely spread over quite a few months, I have a little side project I would appreciate any thoughts on before I go ahead?

I was given a little Aldi wood fire pizza oven for Christmas, as an interim oven to use while the larger oven is being built. I?ve opened the box and given it a short trial fire to see how it went, but didn?t cook anything in it as yet. I think this thing has potential (relative), but I also think it has quite a few design flaws so I?m planning a number of modifications to make it usable for the purpose of small pizzas only. I?ve attached a stock photo to get an idea of what it looks like.

So, as an overview:
- 500mm external diameter base, appears to be kiln fired clay.
- Overall weight would be under 20kg (approx.), so not a lot of thermal mass.
- The base appears to be significantly thicker than the dome walls, at a guess, base about 25mm and walls 12mm or so. The opening has a thicker rim, I think mainly for strength.
- The vent/chimney is poorly located with a lot of flame and heat exiting before circulating within the oven
- The top of the entry is at about 45% of internal dome height. I haven?t measured the opening height but approx. 130mm with width about 280mm
- The internal floor is unglazed so when I rub a finger on it there is obvious clay dust. No cooking direct on that floor I think
- With the trial fire, heat loss from the walls was rapid

I think it?s a real shame they didn?t consider the design of the oven because if they just did away with the vent and had the top of the entry at approx. 63% dome height, it would have a lot more promise. Anyway?

The plan is this..
1) Block the vent. To do this I?ll just place a fire brick on top as a non-permanent solution. It sits there quite comfortably and stable, but not a completely tight seal. I may use a 2/3 brick which will allow some venting if needed.
2) Insulate the whole thing, as much as possible with vermicrete. To do this I will cover the external walls with aluminium foil and then around 100mm vermicrete. Stucco for a final layer to waterproof as much as possible. I was thinking of putting on one layer of ceramic blanket but I really want to keep the cost down on this if possible. Same goes for the base, was thinking ceramic board, but I think a vermicrete layer will do?
3) Line the internal floor with thin firebricks/tiles to allow for floor cooking. I?ll see what I can find and then trim them to fit.
4) Not use the steel frame it comes with and have it sitting on a stacked besser block stand. I?m thinking putting a 120mm vermicrete layer on a sheet of fibrocement board to allow it to be movable. If it works out, I may make a trolley to put it on
5) Total budget for this.. AU$100

So what do you think? Any obvious errors or oversights? Does it need more thermal mass? Will the clay stand up to increased heating by insulating it? Anything different I could consider? Am I just flogging a dead horse?!

All comments will be greatly appreciated.
Cheers
Darius

[david s]

Re: Thoughs with small WFO mods?

This sounds like a pretty good plan to me. Aone piece oven like this is subject to big thermal stress so insulating both under and over it will help reduce these stresses as well as improving its performance. I think you are wise not to go to the expense of ceramic blanket. For the under floor vermicrete use 5:1. I use a vermiculite,perlite, cement, water, clay mix 5:5:1:3:.03 over the dome. This makes a pretty workable mix that will stand up vertically, but still pretty lean. Remember that 1/3 of the volume is water which is best eliminated before doing the outer render.
What is the door height to internal dome height ratio? You may be able to fabricate a flue at the front.
I hope you report back your progress.

[cobblerdave]

Re: Thoughs with small WFO mods?

G'day
Chapala Large BBQ Pizza Oven I/N 3180436 | Bunnings Warehouse

Seen this at bunnings and thought the same thing...how would this work with a proper insulation top and bottom.
The bunnings one at that price its a bit "exy ". But being given one like it I recon you could make it work.
I'd leave putting the firebrick tile in till its tested and needed myself, it will cut down your entrance to interior height.
Cut down that base insulation to 100 mm that's equal to 50 mm of cal sil and the dome do 75 mm and see how it works. You can always add more later
Watching with interest
Regards dave

[dariusk]

Re: Thoughs with small WFO mods?

Thanks for the replies David S and Cobblerdave. It sounds like I'm generally on the right track then. My expectations are not too high with this but we'll see how it goes

David S, the door height is 95mm and internal dome height is 230mm, so 41%. Not great I'm guessing. But will it work well enough...? That's an interesting mix for the dome insulation, particularly the 0.03 of clay. Are there any significant benefits with your formula? I was thinking just a 5:1 vermicrete for the base and either the same ratio for the dome or maybe 7:1 or so. I was thinking vermicrete as it's just a bag of each to get the job done.
I'm not really planning on a flue at the front as I don't want to over work this but will see if it's worthwhile after a bit of testing. Yes, I'll give an update with pics once it's done too.

Cobblerdave, I saw that oven in Bunnings as well. That one is a little bigger than the one I have, though I can't recall the dimensions. The design looks better than mine though. I also thought they were asking a lot for what it is. The one I have was advertised $99 from Aldi and I've also seen them on eBay etc as well for about the same price.
The 100mm for the base and 75mm for dome sounds good to me, I'll go with that

I wasn't sure about the foil barrier over the dome but as not critiqued I'm guessing it's ok.

Thanks again guys and I'll update once progress made

[david s]

Re: Thoughs with small WFO mods?

David S, the door height is 95mm and internal dome height is 230mm, so 41%. Not great I'm guessing. But will it work well enough...? That's an interesting mix for the dome insulation, particularly the 0.03 of clay. Are there any significant benefits with your formula? I was thinking just a 5:1 vermicrete for the base and either the same ratio for the dome or maybe 7:1 or so.

It is tempting to keep adding more cement in an effort to make a workable mix. This is a mistake because it drastically reduces the insulating capacity of the mix. 10:1 is still ok but a mixture of half perlite half vermiculite is way better than either of them alone. It may not be worth buying a 100 L bag of each so you can use just vermiculite or just perlite.The addition of clay also helps make the mix more workable.
If you put more floor bricks in to try to thicken the floor, it will reduce an already small oven mouth. It may be better to place the extra floor tiles between the vermicrete floor slab and the oven or cast about an inch of lime rich concrete slab over the vermicrete, then set the oven on this.

[TropicalCoasting]

Re: Thoughs with small WFO mods?

- The opening has a thicker rim, I think mainly for strength.

The lip will make it hard to get pizzas in and out (harder to get out)
Maybe a pizza stone/tile (squared up to the inside front edge) wont take away too much room and give you an easier to use oven,it will take longer to heat though.

[dariusk]

Re: Thoughs with small WFO mods?

If you put more floor bricks in to try to thicken the floor, it will reduce an already small oven mouth. It may be better to place the extra floor tiles between the vermicrete floor slab and the oven or cast about an inch of lime rich concrete slab over the vermicrete, then set the oven on this.

I will keep the workability aspects in mind and not add additional cement. I may consider the perlite & clay as well. Thanks for that.
The thought behind adding in the thin firebricks or tiles is mainly to get an oven floor that's suitable for pizza dough directly onto it without picking up particles of clay. I have a 25cm pizza pan I could use but I though it would be nice to get some direct contact with a stone/tile. Door width is around 28cm so nothing wider will fit in!
As the walls of the dome are quite thin I wouldn't have thought added mass in the floor only would have any real value and just use more fuel? The plan is to add as thin as possible bricks/tiles etc. The max. thickness I'd consider would be 25mm but havent look around yet to see if they are available. That thickness would bring the floor up to 5mm or so above the door lip. Not sure if it's a good way to go though..

TropicalCoasting, one of the first things I tried to do was insert a pizza stone in there... Problem is the circular stone I have is 30cm ish wide and donesn't fit through the door! It's a good thought though and probably the ideal thickness for an oven of this size. Has anyone tried to cut a commercial pizza stone before? Do they cut well or shatter? The idea would be, as you said, cut a section off, insert and spin around so the new flat edge comes up against the front, reducing the height of the lip.

I'd be interested if anyone knows of tiles, not too thick, that would be suitable and generally available to use as a cooking surface??

Cheers all
Darius

[david s]

Re: Thoughs with small WFO mods?

I tried a pizza stone in my first oven, but it cracked right down the middle. It was only about 8 mm thick. You could try a kiln shelf. They are around 20 mm thick. you should be able to cut any refractory with a diamond blade on an angle grinder.

[wotavidone]

Re: Thoughs with small WFO mods?

I use a sawn sandstone paver from bunnings (about $6) for a pizza stone in the kitchen.
These are natural rock, and if memory serves they are 300mm by 300mm by 15mm.
If your door is 280mm, you might be able to get one of these in across the diagonal.
When my oven was young, for the first 10 or 12 firings I couldn't get the floor hot enough for a decent crip crust, so I used the stone in there until the under-floor dried properly.
I still put it in the white oven occaisonally, it's a great way to clean it. It restores the stone to near pristine condition - no cracking issues so far, and even if it does crack its only $6.
I toyed with the idea of "paving" the floor of my oven with these things, they would certainly look cool. But I was jumping the gun, once the floor dried the bricks perform quite satisfactorily.

[dariusk]

Re: Thoughs with small WFO mods?

David S, I was thinking the pizza stone may not hold up well so I'll try a the 25mm bricks mentioned below.

Wotavidone, the 280mm is an absolute max. width, so don't think it would fit. Do you get any sand or grit etc from cooking direct on sandstone? I'm not a fan of raspberries so it has me a bit concerned!

Alright, I've committed now and gathered up all the materials I should need! Bag of cement, 100L bag vermiculite, fibrocement sheet and a couple of pieces of timber for the form work. I even went out and found a couple 250 x 145 x 25mm firebricks I'll try for the cooking surface. Don't ask me how much the two bricks cost... Ouch! The shop was conveniently located though. I'll use a couple of regular firebrick pieces shaped to hold them in place. Hopefully it will be worthwhile. To date I'm in it for $90.50 and have everything else I should need I think. I'll try to get the base done this weekend. Will update shortly..

Thanks for all the help, appreciated

[wotavidone]

Re: Thoughs with small WFO mods?

No issues with grit from the sandstone. I simply brought it home, washed it and air dried it for a few days.
I last used it on New Years day in the kitchen. We'd had the pizza night on New Years Eve and I had a few leftover toppings and dough-balls.
So I put the stone under my gas stove griller, got it smoking hot, and made four pizzas. These went into the freezer, and they're now lunches for work.
A frozen homemade pizza is way better than a bought one.

Now, I must whisper the next bit, lest I be stoned for heresy....
The pizzas I make on my stone in the kitchen are every bit as good as the ones I make in the WFO - I swear the guys at work who praise my WFO pizzas can't tell the difference.

BTW- The dough was 48 hours old by the time I used it in the kitchen - works really well.

[Greenman]

Re: Thoughs with small WFO mods?

Now, I must whisper the next bit, lest I be stoned for heresy....
The pizzas I make on my stone in the kitchen are every bit as good as the ones I make in the WFO - I swear the guys at work who praise my WFO pizzas can't tell the difference.

We know how hot it has been in SA but really? You should seek professional help or stay out of the sun when you are drinking that potent Claire Valley red.

[wotavidone]

Re: Thoughs with small WFO mods?

Heh, heh. My brother-in-law's GF works for a sort of nature park/reserve. Their fund-raising committee has some connection with a Clare Valley winery and she is able to buy wines left over from their wine tasting nights. I often find myself receiving prime reds for Christmas, birthdays, etc.

[dariusk]

Re: Thoughs with small WFO mods?

Hey there Wotavidone, I hope my pizzas from the WFO are better than the ones from the kitchen oven... It would be a lot of effort for little return otherwise!

I managed to get the base down today. Lots of rainy days of recent and looking like more. I have it covered at the moment. Any ideas on how long I should leave it before starting with the next phase?

Here's a pic and will update further once more done.

[david s]

Re: Thoughs with small WFO mods?

It will dry out far better if left uncovered and exposed to sun and wind if possible. This might take 3 weeks in ideal conditions. If you can't do that because of time or weather constraints then heat from your fire is the other option and this will also take weeks. You will find your oven performance gradually improve during this time.