Mortar for outdoor bake oven?

[Dan_Johansson]

What do you think about the insulation in the link below?

[link]

Probably works, but the online store didn't give the best vibes... Do you live near their physical store?

Edit: found where I shopped from;
http://shop.pleldfast.se/eldfast-material/insulfrax-s-blanket-1

 

[Serjon1]

Probably works, but the online store didn't give off the best vibes... Do you live near their physical store?

Edit: found where I bought from;
[link]

Unfortunately, I live far away.... I'll have to sleep on it for a while

 

[Serjon1]

Hello again!
I'm about to order refractory mortar... I read in a previous thread that about 60 kilos are needed. Did these calculations turn out to be correct?

I'm not sure whether to order ready-made mortar or mix my own. I already have the leftover sand from when I mixed the concrete, but I'm unsure if that sand is suitable for the refractory mortar. How particular do you need to be with the right sand?

All the best!

 

[johanras]

Hello! Unfortunately, I don't quite remember how much mortar was used, but I guess around 80+ kg. I bought a bag of stove clay, I think it was 15 kg, and there was about 3 kg left over. Based on the recipe I mention in post 7, it should total around that amount. I couldn't find any fireproof mortar to buy by the bag, so I chose to mix it myself and was very pleased with this. I bought the stove clay from a stove maker. There's probably a lot to say about the sand, I understand it is very important, but I'm not knowledgeable enough to comment. I chose to buy Weber's sand by the bag mentioned in post 7. It turned out to be a very nice mortar that was lovely to work with.

 

[Serjon1]

Hello! Unfortunately, I don't really remember how much mortar was used but I guess around 80+ kg. I bought a bag of tile stove clay, I think it was 15 kg and about 3 kg was left over. If you calculate according to the recipe I mentioned in post 7, it should come to around that total. I couldn't find any refractory mortar to buy in a bag, so I chose to mix it myself and was very pleased with this. I bought the tile stove clay from a stove maker. The sand, one could probably talk about for a long time, it has great significance I understand, but I am not knowledgeable enough to comment. I chose to buy Weber's sand in a bag mentioned in post 7. It became a very nice mortar that was delightful to work with.

Thanks Johan! Then I'll mix it myself too. With that quantity, it becomes significantly cheaper. All the best!

 

[Serjon1]

Hello again!
I am almost finished with the oven. I am planning to lay tiles on the "table" that the oven stands on and mosaic on the dome. All these surfaces currently consist of vermiculite. Did you paint waterproofing on the vermiculite and how long did you let it dry before?

I hope and believe that this will be my last question, then I'll post pictures and stop bothering you with questions
All the best!

 

[johanras]

Great to hear things are moving forward!
I didn't use a waterproofing layer but instead applied mortar directly on the vermiculite and on top of that limestone slabs around the oven. I thought that water seeping under the stones would indeed dampen the vermiculite but that it would dry when the oven is in use. In winter, I make sure the oven is covered and completely dry before covering to reduce the risk of frost damage.

 

[Serjon1]

Great to hear it's moving forward!
I didn't use a waterproof layer but applied mortar directly on the vermiculite and placed limestone slabs around the oven. I figured that water that seeps in under the stones will indeed moisten the vermiculite, but it will dry when the oven is used. In winter, I make sure the oven is covered and completely dry before covering to reduce the risk of frost damage.

Thanks for the response! I'll do the same then!
All the best!

 

[Ganlet]

The recipe I used was: sand (chose weber dried 0-4mm) + portland cement + lime (weber släckt murkalk E) + kakelugnslera in the ratio 5:1:1:1. It is debated on fornobravo about the amount of sand and a commonly older recipe is 3 parts sand to 1 part others.

Trying to ensure what fire clay in the homebrew recipe corresponds to in Sweden, are you sure it's kakelugnslera? It's a jungle within cement/mortar indeed...

 

[johanras]

Now it's been a while since I thoroughly read everything about this, but I concluded that kakelugnslera was the most suitable. There was another type of powdered clay available for purchase, but it contained iron filings, and I didn't want to use that.

 

[Ganlet]

Now, it was a while ago that I thoroughly read everything about this, but I concluded that stove clay was the best fit. There was another type of powder clay available to buy, but it had iron filings in it, and I didn't want to use that.

I have also come to the same conclusion this evening, at least 98%. As I understand it, it should be just pure dried clay involved. Stove clay seems to be the same, at most diluted with something. I've seen examples where they refer to around >60% clay if I remember correctly.

For a long time, I considered refractory clay like F53, but it felt more like something cement-like.

 

[johanras]

Tiled stove clay is dried clay in fine powder form. Bought a bag of about 15 kg which was enough. It was not available at the hardware store, so I bought it from a tiled stove renovator.

 

[Rosenlund99]

Fun to hear that you're going to start building. It's incredibly fun but can be quite exhausting. I should have followed up the thread with some results earlier but it hasn't happened until now. The oven was essentially completed in the summer of 2015 and has been used quite a bit since then. Mostly for baking pizza, but also other food and bread. What's left is the mosaic over the dome, and I plan to do that this summer. I decided to make my own refractory mortar according to a recipe on fornobravo, but I also considered doing as Claes Sörmland suggests. The problem was getting chamotte sand, and since so many others on fornobravo mix their own mortar successfully, I did the same. The temperature in the oven reaches about 500-550 degrees (I haven't measured the wall temp) at its peak when you fire it up properly. The recipe I used was: sand (chose weber dried 0-4mm) + Portland cement + lime (weber slaked lime E) + stove clay in a ratio of 5:1:1:1. It's debated on fornobravo about the amount of sand, and an older recipe usually is 3 parts sand to 1 part of the others. The mortar is incredibly nice to work with. Plastic and holds the stones well. I could build the entire dome without form thanks to the mortar's properties. Just hold the stones for a few seconds, and they stick to their place. Remember to wet the stones beforehand.

I bought fire bricks in normal size and sawed each brick into 2 pieces using a Husqvarna stone saw with water. The stones were cut with the help of a homemade jig in two angles so they could be laid without mortar in the butt joints (each row holds itself up even without the mortar) and so that there were no gaps at the top of each layer between the stones (as each layer is smaller at the top than at the bottom as the circle narrows towards the top). No mortar between the stones on the inside of the oven.

At the bottom, an insulated slab. On that, Leca blocks reinforced vertically and with holes filled with concrete. On the Leca block support, I poured an upper slab/table, and on top of this, a layer of insulating concrete made of vermiculite and Portland cement in a ratio of 5:1. On this, leveling with stove clay and chamotte sand from the sawing, then the oven itself was built. Insulation on the dome first with rock wool fireproof mat to create a moving joint and on top of that insulating vermiculite concrete in a weaker mix of 10:1. On top of that, plaster and the mosaic will be added later. I’ll try to include some pictures in a separate post.

Ask if you have any questions. There are lots of good people on fornobravo to discuss with. Regards

Hi! I'm wondering about the last layer of mortar you laid on top of the fireproof mat. You write that you mixed 10:1, assuming it was 10 parts Vermiculite and 1 part concrete. What type of concrete did you use? Did you finish the surface with regular plaster or did you use refractory mortar from, for example, Finja Betong? I have a pizza oven that I'm going to renovate due to significant cracking and have removed all material down to the brick. Originally, there was no insulation mat, but I'm considering adding it to prevent cracking in the future.
Thanks in advance, Sarah

 

[johanras]

Hi Sarah,
I mixed portland cement with vermiculite and water to the right porridge consistency and applied a thick layer of it on top of the fire blanket. It becomes an insulating concrete and on top of this, I applied regular plaster.

Johan

 

[Rosenlund99]

Hi Sarah, I mixed Portland cement with vermiculite and water to a suitable porridge-like consistency and applied a thick layer of it on the outside of the fire blanket. It becomes an insulating concrete and on top of this, I applied regular plaster.

Johan

Thanks for the answer!! I've ordered Vermiculite and a ceramic blanket so I'll get started as soon as the stuff arrives! Pizza season is approaching!