Round shape

[david s]

Re: Round shape

I think a 10:1 vermicrete will support the flue better than blanket, easier to form a shape and cheaper too.

[Mike D]

Re: Round shape

Yea your right it would support the flue better (I was just talking about my previous plans), I am wondering if it will create a problem with heating up the outer red brick enclosure (bad heat break).

Mike

[david s]

Re: Round shape

Ok, I see. Perhaps a small piece of blanket where the flue almost touches the bricks would be a good solution as the blanket is a better insulator and the space is really thin.

[brickie in oz]

Re: Round shape

What about blanket and refractory cement kind of like a plaster cast for a broken bone?

[chidding]

Re: Round shape

What about blanket and refractory cement kind of like a plaster cast for a broken bone?

Do this..

I find vermicrete to be alot less effective than everyone here makes it out to be..

[david s]

Re: Round shape

It's effectiveness is reduced by the amount of cement added and if damp. A rough rule of thumb is that you need double the thickness to achieve the same insulating value as blanket. It's advantage is that it is not classed as carcinogenic like fibre blanket.

[Mike D]

Re: Round shape

I could add the Vermicucrete all over except between the front small gap, would that help? I have three boxes of fire blanket, that should be plenty do what ever I want or need to do.

Mike

[david s]

Re: Round shape

I could add the Vermicucrete all over except between the front small gap, would that help? I have three boxes of fire blanket, that should be plenty do what ever I want or need to do.

Mike

That's what I'd do.

[Mike D]

Re: Round shape

-Sorry guys I have been backed up and have not posted how things have been going. Here is what is going on.

-I put a vermicucrete collar around the ceramic flue to give it a little more support.

-I added the insulation (3 boxes), I thought it would go farther, but I plan on filling the excess space with vermiculite.

-I started the curing process, Here is a pic of the first fire (news paper only).

mike

[Mike D]

Re: Round shape

Now to bring me up to date-

I have been making fires over the past weeks, making each one bigger than the next. I should of read that curing fire thread all the way though before I started because those first 2 fires probably didn't do anything. As my fires got bigger the heat did what I was afraid it was going to do to the brick in the front (I think I knew when I was trying to put the insulation in-between the red brick and the flue). I got a small crack starting from the outer arch up though the red brick. Obviously as the arch got hot and expanded it lifted the red brick. The crack is only visible on the outside of the arch (on the fire brick), it does not go into the dome.

-On a good note, I don't have any other cracks (knock on wood) inside the dome.

- The dome is just starting to clear. I haven't gotten it to totally clear just yet, the weather is not cooperating. The last picture is of the top clearing.

- My plan was to get the dome to completely clear before I tried to fix the crack. (If that is even possible). The crack gets slightly bigger when it gets hot (no big surprise there).

Mike

[brickie in oz]

Re: Round shape

Did you see the fire dog in the pic, no enhancement, it looks like a bulldog.

Im a little confused as why the arch cracked, the oven is insulated and no big fire was lit?

[Mike D]

Re: Round shape

I got a good fire going, as in the dome started to clear, so it was hot and the front of the oven (red brick) was getting warm.

Mike

[brickie in oz]

Re: Round shape

Those red bricks you used look vitrified, it takes an awful lot of pressure to crack them even with a hammer.....

[david s]

Re: Round shape

One side getting hot and expanding the other side cold, not good. This is often the cause of cracks. My first oven developed a crack in the firebrick floor at the entry. This brick never got really hot like the floor bricks in the centre, but being cold at the front and hotter where it was nearer the inside of the oven was probably the cause. If you heat refractory material unevenly there will be uneven expansion, particularly when the rate of temp rise (300 C/hr) is so rapid.

I should have explained that my first oven had no entry (centre flue for saving space and simplicity) so the floor brick was half in the oven and half out.

[Mike D]

Re: Round shape

I am less worried about the fire brick part of the crack (it is so small). The crack in the red brick Just looks bad and it makes a way for water to get in when it rains.

-Any ideas how to fix it?

Mike