Question about cracks

[cholme]

Re: Question about cracks

David,

That is interesting, I guess that area is prone to more stress and movement.

I haven't had much of a chance to do too much since my last post. I did one more firing to about 725deg, the cracks that are already there open up a tiny bit when it is hot but I didn't notice any major new ones. I am hoping to insulate and enclose in the next couple weeks.

... My wife is having second thoughts on the finish design, so it is a bit up in the air right now.

[david s]

Re: Question about cracks

I have also been following this thread with interest. It won't help you, but I was interested to see that the cracks in your oven are precisely where I designed the joins in my oven casting.

[azpizzanut]

Re: Question about cracks

Hi All,

I've been following this thread with interest. I agree with SCChris, you're almost there. Maybe another couple of fires and it'll be dry as an Arizona haboob.

Cheers,

[SCChris]

Re: Question about cracks

Cholme,

I think the oven is gold at this point and running a light in the oven won't get you anything except a bigger electricity bill.

Enjoy!!

Chris

[cholme]

Re: Question about cracks

Thank you guys so much for your input. On further inspection, I don't think my crack goes through to the inner part. At the chain that has the crack, I switched from using my "indispensable tool" to a form so I wasn't able to clean the mortar off as well as the lower chains. As a result, there is a bit of mortar standing proud from the bricks which makes it so the soot has a void.

I am at 1 week, 6 fires up to 650deg. I am away this weekend so I put a high wattage bulb for a couple days. No further cracks, my patches are holding. When I get back, I will insulate and finish the enclosure.

In the home stretch.

[Neil2]

Re: Question about cracks

"It feels pretty solid, I don't feel any loose bricks. Should I press on and continue my cure, or should I not?"

Carry on. Keep an eye on any changes, loose bricks, or crack increases, but I think you will be OK.

[david s]

Re: Question about cracks

Problem with a thin slurry is that extra water means more shrinkage. A clay only mixture is also going to result in high shrinkage. If you can add about 50% aggregate (finest sand you can get) it will result in a mix that won't shrink too much.

[brickie in oz]

Re: Question about cracks

I fairly sure it wont collapse so patch the outside and press on, itll still cook ok.

It actually takes a lot to get brickwork to fall over if there are no lateral forces at play.

[cholme]

Re: Question about cracks

Upon further inspection, the crack does go through to the inside of the oven. It is, oddly, only on one of the chains, the rest look fine. I wasn't noticing any smoke coming out, but I did patch the outside.

It feels pretty solid, I don't feel any loose bricks. Should I press on and continue my cure, or should I not? I hope this doesn't mean I have to dig out and re-mortar, re-cure etc... but if it does, so be it.

Thanks,

Chris

[cholme]

Re: Question about cracks

It does look a little damp in places to me too. The dome was completed 3 weeks ago. I let it cure damp for 1 week, then took the blanket off and let it sit for another week. I live in the San Fernando Valley (Southern California) and it has been about 90+ deg so I don't know why it would still be wet... particularly toward the bottom. The bottom was done 5 weeks ago.

I need to let the inside cool to check if the crack goes all the way through.

I do appreciate all the input.

Chris

[brickie in oz]

Re: Question about cracks

Don't you think some of that mortar looks damp???

Some of it looks damp to me.

[Cheesesteak]

Re: Question about cracks

The reason for a warm patch up is that the oven/crack is already expanded and the slurry will fill the expanded crack, if you patch when its cold the oven will expand and so will the crack.

I don't disagree with the method at all . . . I'm just pointing out that a warm/hot oven will result in a rapid moisture loss in the mortar which will likely mean it will be very weak. I was wondering, out loud, whether a slurry of fireclay would work as well - maybe better. I don't know . . . I'm just thinking out loud.

Don't you think some of that mortar looks damp???

[brickie in oz]

Re: Question about cracks

The reason for a warm patch up is that the oven/crack is already expanded and the slurry will fill the expanded crack, if you patch when its cold the oven will expand and so will the crack.

[Cheesesteak]

Re: Question about cracks

You're pictures might be deceiving me - but it looks like you can still see some moisture in the joints at the top of the oven. Is that the case - or is the mortar just a different color?

I'm not sure about your case - but I think some people get in a rush to light a fire once the dome is done. The mortar might appear dry - but it's still gaining strength for quite some time. I've read that mortar should moisture cure for a week or so. With a WFO - you're not just putting that mortar to "normal" use - its much more extreme.

I let me oven bake in the sun for weeks before I started any curing. Then - I went to an electric hotplate for a couple of days - then on to fires. I didn't measure fire temperatures - because fire temps raise / lower significantly with airflow and fuel changes - even when you just turn the logs over.

I would try to patch the cracks as much as possible - but it's really not going to "fix" the cracks. When you apply the mortar when the oven is "warm," the moisture is going to be driven from the mix - and you wont get much strength out of it. I almost think you'd be better off with a fireclay slurry - and let that get down into the cracks.

I would also wait to insulate until you've had an opportunity to fire the oven up at least once to full temps for an extended period. That'll tell you what the real impacts of those cracks are. Might not be much at all - then you can just cover with insulation and go from there.

Pizzas will still taste as good . . .

[Neil2]

Re: Question about cracks

Almost all brick oven crack to a degree. Judging by your photos, yours has cracked a bit more than most. I don't think you have to worry though. Patch it up as brickie suggests and monitor it closely for the rest of the curing firing process. Check the inside, what you should watch for is if any bricks appear to have dislodged inward.