Crack between chimney and front face

Good morning after my first cureing fire Last night In which the dome above the fire inside stayed around 300 degrees then when the fire went out I put the door on for the night and this morning I see this crack that formed between the chimney and the front face… this is the crack inside and the stucco on the outside has a hair line crack as well. Is this a normal place for a crack? My plan for now is to leave it finish the cureing and let everything settle for a bunch of cooks before I try to fill it… that is unless you guys think it needs to be filled now? The oven spent a week in the mould then about a week exposed to the air before i put the insulation and stucco on… also the directions said 3 layers of blanket but i only had enoufgh to do 2 layers… after the fire quit last
night the outside of the dome stucco was 100 degrees is this also normal?

Hi, Joe, and welcome to the BrickWood forums!

I am inclined to agree with your plan, at least through the curing stage. You certainly gave your casting enough time to set up before you insulated it. Others with a Cupola may have observations to share, but in general I’d say that seems like a likely spot for a crack.

I would repair it with a silicone product before you start cooking. Although this link is more about the Mattone Barile ovens, the two products it mentions are useful. I’ve used the DAP, but in your case I’d go with the Rutland product.

With either product, I would apply it before the final curing fire, and use a disposable plastic putty knife to work it into the crack. They require heat in order to cure.

You can, and should, use a stucco patch product available in the paint section of a hardware store to repair the crack in the stucco, and once it cures (which won’t be too long, see the label directions) paint over it. The stucco protects your insulation from moisture intrusion, which otherwise would cause steam to build up.

As for the insulation, I’ll just say that if the spec calls for 3 layers and you only did two, you might find the outside to be warm. You’ll lose some more heat from the oven cavity because there isn’t as much of a thermal break between the inside and the outside of the oven.

The crack is a minor repair, and I hope that once it’s filled up and you get into cooking that you enjoy your new oven! Let us know how it goes, Joe,

1 Like

@bikerbudmatt - 100% Correct! Thank You!

1 Like

Great ty for the reply I will fill them tonight. As for the insulation would it be possible to add 2 more layers of blanket then another layer of chicken wire and more stucco? In the end the plan is to finish it with a brick surround and roof.

If you have surrounding space on your hearth slab to support it, sure, that would work fine. Thinking about the “footprint” that mineral fiber and stucco will need, you would need (very approximately) 5 inches all around. The temptation will be to compact the mineral fiber so it takes up less space projecting out around the shell. You should resist temptation—like any fiber insulation the blanket works by trapping air and using it to slow convection of heat through its space. It needs “loft” to do that.

If in doubt about the space available for a footprint, I’d go with the single layer that you missed before. Thinking about it, you have surrounded your 800 or 900°F oven interior with a blanket that is slowing most convection and resulting in a 100°F measurable temperature on the current outer shell. You don’t have to capture all of that again, just the loss on the current outside. A single layer should be sufficient.

I’d also consider tacking that layer to the original stucco with a temporary adhesive, just to make application easier. If you have anything like a tube of heat-resistant silicone, a few thin lines just before you lay down the blanket will keep things from slipping. This is NOT recommended for the primary blankets, which are over a castable shell or firebrick, because the fiber needs to expand, contract, and “breathe” over the hot surface. But it’s fine over the stucco.

Finally, as you suggest, do add the layer of “chicken wire matrix” over your new insulation, or the new outer stucco shell will fail.

Hope this is all helpful as you finish your work, Joe!

1 Like

Awsome thanks again! I think I am on track to get where it needs to be!