Crack Repairs - No smoke escaping, are they needed?

[fornoa]

I waited a month before starting to cure my oven yesterday. The oven has been uncovered during dry days and covered each night.

The oven is built of firebrick resting on a layer of insulating firebricks. It is a vault design with a square floor area of approx 1.3 sq meters. Also, I bagged the external part of the vault and wall with approx 1 to 5mm of render after finishing laying bricks. I have not yet insulated the oven, preferring to cure before doing so. My idea being that any residual moisture would not be trapped under the insulation and render layers.

I started the curing fire in the middle of the hearth with just a few sticks at first, keeping the fire small. Using my infrared thermometer gun, I found that the fire was barely heating the dome after 1 hour with the temperature just reaching 100C at the top of the dome and only 70-80C at eith end of the vault. The walls were even cooler at around 40C.

I decided to ramp up the fire a little and soon after I notice thickish (0.5mm) hairline cracking along the spine of the vault and further down either side of the vault, with one crack near the doorway being more severe than the others at approc 1mm. The temperature at the top of the vault reached 170C.

I kept checking for any escaping smoke or steam, but there was no evidence of either.

Considering that no smoke was escaping from the cracks created, I assume that I would not need to make any repairs. Does anyone have any advice regarding this?

[cobblerdave]

Re: Crack Repairs - No smoke escaping, are they needed?

Gudday
Yep all ovens crack.. thats what they say,and its good you don't sound to worried. I'd heat my oven up again so the cracks are there largest and get some of you heatproof mortar in them.....or leave them if they close up when its cold. Either way your oven will not fall down due to some hairline cracks

Regards Dave

[fornoa]

Re: Crack Repairs - No smoke escaping, are they needed?

Hi Cobblerdave,

Thanks for the reply.

I figured I didn't have much to worry about, however it is nice to bounce it off the forum.

The cracks are still too fine to apply any mortar however, as you mentioned I should know more after I ramp up the temp in a few days time.

Will post my results as they occur.

Thanks for the input. It's appreciated.

[Aussie Pete]

Re: Crack Repairs - No smoke escaping, are they needed?

Everyone has said that hairline fractures are present in most ovens and its nothing to worry about....but...does this have to be true?. Surely an oven would be better without any cracks what so ever. Isn't there a fool proof formula for curing that wont leave any cracks whether big or small.
I too am planning on slowly curing my oven without the insulating blanket installed, to try and eliminate moisture from first layer (as much as possible anyway).
I just wonder if Fornoa your oven cracked because you only had 1-5mm of render ontop of your bricks layed (is that thick enough?).

I know the oven expands & contracts, but surely theres methods & procedures and even materials that could/would eliminate cracks..

Surely...an oven is more structurally sound if it doesnt have fractures.

I'm probably thinking of an instance if a bricklayer was building your brick wall for your house, and you saw cracks all through the wall...."would you be happy"..(possibly a bit different scenario perhaps)

[brickie in oz]

Re: Crack Repairs - No smoke escaping, are they needed?

I'm probably thinking of an instance if a bricklayer was building your brick wall for your house, and you saw cracks all through the wall...."would you be happy"..(possibly a bit different scenario perhaps)

Thats why I use air set high temp glue rather than home made muck.
Its the mortar that gives way, not the bricks.

[Aussie Pete]

Re: Crack Repairs - No smoke escaping, are they needed?

"air set high temp glue".....do you mean refractory cement, is that the same thing?.
Thats what i was going to use for my oven build.

[brickie in oz]

Re: Crack Repairs - No smoke escaping, are they needed?

Sounds the same, comes in a 20kg tub and costs about $30.
Water it down a tad as its too thick straight from the tub, put water in the tub on top of the glue to help keep it when not in use.

And looks like this.

[Aussie Pete]

Re: Crack Repairs - No smoke escaping, are they needed?

mmm..ok, the stuff i'm going to use is in a bag form, refractory cement, you just add water (bit like render), will try and get pic of it and post up.

[Aussie Pete]

Re: Crack Repairs - No smoke escaping, are they needed?

oh yeh...forgot to ask....what is stucco?...is that what we call render.

[brickie in oz]

Re: Crack Repairs - No smoke escaping, are they needed?

mmm..ok, the stuff i'm going to use is in a bag form, refractory cement, you just add water (bit like render), will try and get pic of it and post up.

I wouldnt use it, it wont stick and bind like the wet stuff, the wet stuff is hard and set with in about 30 minutes..

oh yeh...forgot to ask....what is stucco?...is that what we call render.

Same beast.