Broken Core

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Broken Core

Postby mannytheseacow » Sat Oct 04, 2014 11:59 pm

Ironically, I was chatting with Drew in Toledo today and he was talking about making a core that broke.

I went to start a fire this evening and found that the whole top of my burn tunnel had fallen off. :?
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I know these things are delicate but I've never lost this much before. It's really a hard place to patch, too, because this stuff doesn't like to stick to dry core.

Thinking back to casting it, this spot had a lot of water glass, refractory mortar and refractory cement.... I wonder if all the additives aren't as dependable as the basic clay/perlite mix?
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Re: Broken Core

Postby hpmer » Sun Oct 05, 2014 12:40 am

manny,

I've had reasonable success getting patches to stick to dry, fired core by wetting it first. I use a spray bottle, spritz, let it absorb for a minute, spritz again, etc.I generally use a clay slip as the spritz.

I agree, though. That is a tough spot. Upside down in the most abused part of the entire system. With my bbq stove I shortened my burn tunnel too much so to patch it I'm going to cast a replacement brick out of the core material (ash and clay in my case). I'm casting it wider than the burn tunnel and then will carve out a little ledge for it to rest on and then patch it in. Maybe something along those lines could work for you.

Good luck.
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Re: Broken Core

Postby matt walker » Mon Oct 06, 2014 1:03 am

Yikes. That's your new 8"? It seems like if you can get them dry they last, but the early days are when things like that might happen, although I've never seen the whole top come down like that. Have you got it patched up? I imagine by now you do. Still, that's a terrible spot to drop out.
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Re: Broken Core

Postby mannytheseacow » Mon Oct 06, 2014 2:18 am

I haven't had time to patch it in yet. I've had a busy weekend with butchering and honey harvesting. I've still been burning and it seems to be working fine. I'll patch it in before too long here.

So hpmer, you put the slip in the spray bottle? I would have thought it would clog the sprayer but if you say it works I'll give it a try. I can easily fit a spray bottle down in there to moisten things up.
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Re: Broken Core

Postby hpmer » Mon Oct 06, 2014 1:58 pm

Yeah, the slip has to be pretty thin. Alternately you could spray plain water for a few rounds to wet the mix and then paint a thicker slip on with a paint brush. I've found the clay adds a bit to help it stick.

If you don't go with the 'brick on a ledge' idea for your patch, you might want to support it underneath until it dries. That's a really tough place as you have gravity working against you.

I've got my cast brick air drying now and plan to fire it before patching it in to minimize the factors that can work against me.
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Re: Broken Core

Postby matt walker » Mon Oct 06, 2014 3:43 pm

Manny, you could also probably easily build up that area in small layers. Before you light it over the next few days smear a handful of mix in there but don't worry too much about building it up. It's way easier to get small amounts to stick than a large chunk, and I think they''ll be less likely to fail as a whole unit. Glad it's still working for you, they are pretty forgiving things generally.
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Re: Broken Core

Postby mannytheseacow » Tue Oct 07, 2014 12:01 am

Thanks for the input, guys. A combination of both methods seems to work. Smearing a small layer makes sense but in practice the pressure needed to smear takes off about as much of the delicate core as I can apply. I made a wet paste and moistened the area a little, then pressed in small amounts. I'll keep doing this in small layers until it's built back up. If that doesn't work I'll make a small cube that I can drop into the burn chamber and slide over, the press in a new roof around it.
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Re: Broken Core

Postby hpmer » Tue Oct 07, 2014 1:30 am

It probably goes without saying, especially for those of you that work with masonry on a regular basis, but a trick I learned through trial and error is that it's much easier to apply the mix if you wet your tool (hand, trowel, drywall knife, etc) before grabbing the mix. And then keep the tool wet by dunking it in a bucket of water regularly. Makes the application nice and smooth, and the mix doesn't stick to your tool and pull more off than you're applying.

Makes it easier to work the mix into tight crevasses when patching as well.
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