Setting the core

[hpmer]

Does it matter if the initial burn to set the core is done in a single burn session vs. multiple shorter sessions?

I'm building a new bbq stove and plan a 3" thick core. Since heat is supposed to move through cob at roughly one inch per hour, getting the heat all the way through is a minimum of a three hour burn, although I expect that longer is needed to really set it once it is up to temperature (?)

Since it is an outdoor cooking stove, it will be used much less frequently, and for shorter periods, than the typical rocket so I wonder if an initial prolonged burn session might be wise to set it all the way through to get it started off on the right foot.

Or does it even matter???

[Donkey]

I usually start a little slower. There's a LOT of water in the cob that's going to take possibly weeks of use to get out of the system.
Get the stove hot, but don't fire it for too long the first couple times. Give it a steam-off time, then start it again.
After a couple of days of this, you can let it rip.
(With Rocket Stoves, I like to run the stove WHILE I'm building it.)

On the other hand, sometimes when the clay is right and the mix is right, you can let it rip, full out right at the beginning and be it'll be solid as a rock from then on.

Experience is gonna tell you one way or the other. Anyway, it's mud and can be patched over or re-built very easily.

[hpmer]

Thanks, Donkey.

In the past I've built and then let them sit for a few weeks before initial firing thinking that turning the imbedded water to steam immediately might force it out too quickly and thus ruin the structure of the surrounding mix. Interesting that you burn WHILE you're building.

[Donkey]

The thing about burning while you build is there are no surprises after it's built. If you drop a big wad of cob in the flow-path, or crush the pipe (or something), you get INSTANT feedback and can easily address the issue on the spot, while it's easy.
Drawbacks are working around hot parts that steam and often smoke actively. I've accidentally made so much steam that the cob super-saturated, became too wet and slumped out. Fortunately, the easy fix is to put out the fire and keep building.
Hot parts will steam off and dry into position faster and can be carved into shape as they dry.