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

[Matthijs]

Hi Sergetania, Thanks for your advise. I do have a curve in the entrance. The center is ~2'' higher than the sides. (See photo) The flue chamber will be directy in from of the dome. I hope to minimize the soot like this. (stole the design from David)

[sergetania]

My top is only 1" higher than the corners for 20" width. Also, try to make the flue entrance wider. Mine is pretty much 6", the diameter of the chimney, right in the center.

[Matthijs]

Small chance of plan. I will cast my dome and door in two parts. This way I can build my flue chamber a bit on top of my door. (See photo) and enables me make the oven bigger and more compact with a shorter and wider entrance.

Is it needed to connect the two parts?
OR would the homebrew connect to the already dryed homebrew dome?
OR does the V-Crete provide enough stability to the connection?

[david s]

The thicker you make the casting the more material you will use and the greater the heat sink effect. If you want to provide a small gap cover the joint with some corrugated cardboard and plastic so you can remove it after casting and fill with lean vermicrete. The vermicrete surrounding it will hold it in place quite well as well as being somewhat flexible because it's not so dense and as strong as the home-brew. I don't do it this way because I've designed my flue gallery to be very thin (it weighs less than 10kg) and is not insulated from the inner dome. it's also well insulated on the outside so the heat sink effect is minimised, but there are lots of ways to do it, just do what you think is best/esiest.

[sergetania]

I cast the dome and the entrance separately, both in place and I just packed the castable concrete to the completed dried dome without a gap. Now if I look I can see a small gap (controlled crack?) It's covered by the ceramic blanket on top of the dome/gallery. Nothing holds them together and I don't think anything could except maybe some sort of flexible high temp adhesive. It seems to be fine.

[Matthijs]

sergetania Yours is one of my example builds, Just asNick J C, Mullister and older builds. Hours and hours of reading. all very interesting but time consuming. I do not have a lot of DIY experiance.
First time I work with concrete. So lots to learn. But the plan is now almost complete (I think)

[sergetania]

Matthijs Thanks a lot! I have got so much help and information from the forum I wanted to give something back. That's why I posted so many pictures thinking someone doing it for the first time (and no prior experience with concrete, just like me) could benefit from it. Of course, it would be so much easier if David has written a book about building a pizza oven Sorry, David, no pressure!

If it's still in the planning phase, may I give you an advice? Of course,if it's too late never mind. Otherwise,if you could make the oven bigger, do it! Maybe it's the "*-American" in me talking. No denying, things in America are done on a different scale, but after enjoying my oven I am glad it's at least 30" inside. Try to stretch yours. If you can't 24" should work for pizza but it will be tight for other things. We have to work with what we can get.

[Matthijs]

Thanks for the advice I only have a small garden. (I have to share it with a wife, 3 kids and a chicken) I think/hope the 24'' should be enough.

[sergetania]

A 12" pizza should fit if you use a small peel. The chicken may feel safe!

[Matthijs]

Made some miles….

Last week I cut the Fire bricks. I used a 115 mm diamond disc.
dropped the stones a few minutes in water before cutting.

The disk was a bit to small but still the cutting went very smooth.

Made a nice bed of 1/1 Sand/Clay (dry).

Also made the entry of the oven.
Packed it with plastic and made sure It is demountable from the inside.


This weekend Saturday I made the mould of the dome with sand. Cannot find the correct English name for the used sand. In NL its called ‘’Metselzand’’ (<3 mm) I think this should be builders sand or sharp sand or concrete sand.

Mixed it up with a little water ~8%w and dumped this on some stones. I made the form (¼ circle with the radius of 30 cm) to keep the dimensions. (see photo
This was an easy job. At the end of the day I had a perfect dome. Already very happy with it.

After this I sticked paper (with wallpaper glue), paper-mache style.

Tip: tear the paper into small stripes. this way I gained a smooth surface.

[Matthijs]

Forgot to mention. Made a heat stop / barrier of ~1 cm just outside the door in the floor. Filled this later with Perlite/Vermiculite/portland 3:3:1.

[Matthijs]

On Sunday I spend my day with brewing the homebrew. 3:1:1:1 with polypropylene fiber (~1 long. As a fortifier I used the AR Glass fiber AR = Alkali resistance (Thanks David S for your article) The length of the fibers is ~3 of 4 cm I think. The idea is these should replace the Stainless Steel melt fibers. I hope this will work.

The amount of these AR glass fibers were a bit of a guess for me. I had a conversation factor 25 kg SS melt fiber equals 5 kg AR glass fiber
supplier info: 1,5 to 15 kg / 1000 l concrete.
In the end I added 50 to 60 gram to every batch of 6 liter.
It looks like I added a lot of grass blades to the homebrew...

I had some doubts on the amount of water to add. I added ~700 ml water on 5400 ml of dry solids.

Can anyone explain the “ball up” thing ????
I believed it you can make a ball with the homebrew. you throw it up and catch it and its stays a ball. The consistency is okay.

Anyway, I think this is the most tricky part of the oven. If I fail there is enough material left for a second try. (To bad of the HARD WORK though).

[Matthijs]

Removed the oven entry last week Monday.(one day after applying the homebrew. (was an exciting moment)) This went well. Was quite tight. I see this as a positive thing.
Then removed the sand. Was a bit afraid I could not get the stones out (that I used as a filler in the mould) as they were quite big. But no problem.

The result is a smooth hard inside. No voids. No cracks. No lumbs.
A lot of hair (glassfibers) sticking out the homebrew. But overall very happy with the result.

spray it with water for a couple of day, keep it damp, and covered with plastic.

[Matthijs]

One week drying I start to design the flue gallery. The idea is to use the Dome wall as the back of the gallery. (see photo).

I made a heat break with Perlite:Vermiculite:Portland 3:3:1 on the front of the dome and were the flue gallery connects with the dome.
(I understand this is not very useful. a bit overengineered)..

Regarding the insulation layers. :

The plan is to use 1'' (2,5 cm) Fire Blanket over the dome and than add 2'' (5 cm) 10:1 V/Pcrete.

- Would this be enough insulation?

- I have bought to much fire blanket, so I can add an extra layer. Would this add much value?

- Is it very important to keep the 'Fluffyness' of the FB intact?

[sergetania]

I would not worry about the fluffyness unless you plan to do something weird. It will be fine as you layer vcrete over. Why not add another layer of blanket if you already have it and have enough room for it? It's only the second layer,it will make the oven better.