Buiding of a 60cm(24'') homebrew oven (NL). Vcrete question.

[Matthijs]

have enough room for it?

Nope, the room is limited will puzzle a bit how far i can go with extra layer.

With the 'fluffyness' I mean, that I can imagine the fire blanket has a better isolating function if not compressed to much. Is this assumption correct?

sergetania
I really like your front or your oven! Looking for tiles like them .

Did you used tiles that are resistant to frost? What would happen if I use standard bathroom tiles break them to mosaic the outer arch. Would frost break them
What ratio did you used to make the front (outer arch) (portland:sand:sealer) any special sand for the white colour?
Would it be possible to add the broken tiles them on a later stage (after I find suitable tiles)

Will post some photo's tomorrow to share the process in progress.

[sergetania]

If you add an extra blanket layer you can reduce the thickness of the vcrete layer above it to 30 mm (according to David) though I don't think it is always easy because that stuff goes on thick. Fluffyness - yes, correct, don't worry about it unless you are doing something weird instead of simply laying on vcrete. You will see what I mean when you get there.

Thanks on the facade! I did a really stupid thing with it. I glued the tiles to the bottom of the form with silicone (see the picture). I have since spent hours scrapping silicone with a razor blade and most of it is still there (I also got lucky with a really fresh tube of silicone!!!). Don't use silicone. I was afraid of the concrete getting under the tiles so I would not be able to see them. Lots of guys on the forum embed stones or glass in the bottom layer when casting and then polish it. You can't do it with tiles. I wonder if it would be easier to cast a facade and then glue tiles to it later and grout. I don't know if they would stay when heated or frozen. No idea on the frost resistance either but they are small pieces and they don't crack when heated. Hopefully ok when frozen. I also like the tiles because it is very easy to clean with a soot cleaner.

I have used a hi-tech countertop concrete mix, same as I used for the hearth foundation and the tabletop next to the oven, with 1/4" rebar. I didn't want to bother with mixing concrete components myself, everything I used was a commercial mix (except pcrete and even then I managed to mess up using electric mixer - don't!). Also, forget the white color - gaps between tiles are now black. Soot only comes easily off the tiles, not off the concrete in between.

Also, make sure you mount the facade like David suggests. Mine has stainless steel wire embedded in it that goes around the chimney adapter and there is a good size gap between the inner cast and the facade.

Good luck!

[Matthijs]

Maybe a stupid question, but would a entry(oven front) of some nice hard wood be an option or would the wood become to hot and break or even catch fire?

Of course I would add a heat break of a ~8 mm between the entry and the front arch just an empty space (or some vermiculite barrier) .

Here a photo of the where the oven front should be made

[Matthijs]

And another one. show the flue gallery. Hope hot air will take this route......

[sergetania]

Looking great!

Judging by my oven, a wooden facade will catch fire very quickly. When you are heating up an oven quickly the fire will go into the chimney. It gets hot, very hot very close to where the facade is.

[Matthijs]

I messed up my concrete front/arch. Therefore I wanted to try to wooden thing. But indeed there must be a good reason why it is hardly used in any part of the oven. I will do a second attempt with the arch.

Wood is used in the oven door sometime wrapped with metal. What metal would be possible to use as oven door":

- galvanized and Brass contain Zinc = very unhealthy
-RVS = expensive.

-aluminium = not very nice looking
-Steel = oxidative
-Copper = Nice


The plan is to make it like this. Only a bit more insulating.
What are the pros and cons with the 3 metals?

[sergetania]

Sorry, too lazy now to find the pictures of the door I have made, please check in my build thread. I have used the same template I have used to build the entrance for a good fit. It has wooden handles and they are absolutely fine after quite a few high temp cooking sessions. I believe it's essential to use stainless steel because it conducts heat very poorly hence the heat is contained in the oven. I have used almost 2-mm thick steel so it stays perfectly flat. Next day after cooking the oven temp is still high enough for baking and slow cooking. I don't need any more insulation, just the stainless steel. Very happy with my door and it was easy to build partially because I used handles from an old useless grill gadget that was supposed to turn a Weber grill into a pizza oven (it didn't!)

[Matthijs]

Some time passed since I posted.. Had a short break during winter.
Oven is almost ready to use. I did a curing/drying tour. 7 days of fire.

I have a question about the heat retaining of the oven.

So yesterday 13:00 to 15:00 hr I had a nice fire burning. The soot in the dome is removed. The dome was ~400 - 500°C the floor also >400°C
after the fire was out I closed my door.
In the evening 19:00 I baked a bread (the oven floor and dome 200 / 230°C)
The next morning the floor and dome was only ~40°C.

my floor is on top of 11 cm (4 inch) 5:1 Vermiculite: portland (no other insulations.)
the dome (incl side of the floor) is cover in two layers of insulation blanket (so two layers of 2.5 cm/ 1'') covered by 2 inch 10:1 Vermiculite: portland

My door is 3 cm 6:1 Vermiculite: portland and wood. (the door does not close very tight. (there are some space at the top of the door ~2mm)

Is it normal the temperature drops in ~17 hr from 400C (750F) to 40°C (100F)?

I can imagine, since the oven is very fresh there is some moisture in the dome (that has a negative impact on heat retaining properties)

Thanks! If all is normal I can start with the stucco layer in the weekend.

ps sergetania I tried planning my follow your arch idea.. I kind of messed-up my first attempt so I decided to 'stick' them on later...

[Kris S]

Hi Matthijs,

I seem to have missed your build while I was researching the forum for the last couple of weeks, I’m close to starting my own 28” build soon.
Good to see someone close by building an oven too, it looks great already!

I have a few questions: since we have exactly the same wet weather in Belgium, how do you plan to keep the oven dry? It seems only applying a stucco render won’t be enough, and sealing it completely shut would trap any moisture inside, creating even more problems. So I can’t see any way around building a walled enclosure, even though I like the look of an Igloo much more.

Also, how did you attach the chimney? Does it just ‘sit’ in the space above your flue gallery?

Good luck with finishing your oven.

Kris

[Matthijs]

Hi Kris,

Good to be able to give some advise. I start to feel like a parasite....

I have a small pipe (on top of the dome) that should help releasing moisture...

I plan use a stucco layer with (a Belgium product ) "Compactuna pro"

https://dpyxfisjd0mft.cloudfront.net...pdf?1515581509

Than I will do some nice mosaic tiles as a extra layer.

My flue just half 'sit' on the gallery. the flue gallery is a bit V shaped. so it locks itself and i made cuts in the flue so it has room to expand. packed it with 5:1 Vcrete and 10:1 Vcrete. as a photo the plans (I stole) than it will make more sence.

[Kris S]

Ah, good old Compaktuna I've used it around our house as well, and have considered using it as stucco, but finally decided against it because of:

As it is not breathable (at least I don't think so?) the moisture trapped within the inner dome and the outer render from the humid air cannot escape.
But, as you say, a vent (pipe) on top of the dome should help with that,

and

There will still, over time, likely appear some small cracks in the outer layer after some use of the oven, as far as I can read on the forum, providing an easy acces route for moisture.
The vent will help drive of moisture, but I fear it might not be enough and a few drying out fires will be needed after winter, which I want to avoid.


It's just that I'm not sure how well such a vent will work in order to avoid having to do the drying out fires. I'm a bit weary.

On the other hand, I don't think I'll finish my oven before summer, so maybe I could delay my enclosure build to next year, after your hopefully positive experience with compaktuna.

I love the mosaic finish look.

I will likely go the same route with attaching the chimney.

[Kris S]

Matthijs, can I ask where you sourced fireclay from? Can’t seem to find it and have to resort to ball clay from a ceramics store, but it should work as well.

Cheers

[Matthijs]

From a local supplier. Also sourced my stones and Vermiculite at the same place.

I have a lot left. Your oven will be a bit bigger than mine. So if ~60% is still in my bag. It might be an option I send it to you. But need to check first.
Also,It might be of your interest. I have some AR-GlassFibers (As replacement of the stainless steel needles). I can not guarantee they work as good as the Stainless steel needles.

[Matthijs]

[repost] See details 4 posts before. Can someone stop my doubts?

Is it normal the temperature drops in ~17 hr from 400C (750F) to 40°C (100F)? (outside temp approx. 5°C)

I can imagine, since the oven is very fresh there is some moisture in the dome (that has a negative impact on heat retaining properties)

Thanks! If all is normal I can start with the stucco layer in the weekend.

ps sergetania I tried planning my follow your arch idea.. I kind of messed-up my first attempt so I decided to 'stick' them on later...

[Kris S]

Just a thought: maybe the smaller than average size of your oven means less heat retaining mass, thus cooling down faster compared to a 30" or 32" oven?

Curious to know the answer as well.

From your pictures it looks like your ovenfloor firebricks are roughly 5 or 6cm thick, so not especially thin I would think...