[Clayart] Wood-gas hybrid kiln firing advice needed

Paul Herman via Clayart clayart at lists.clayartworld.com
Wed Feb 25 17:50:39 EST 2015

Hi Bob,

First, let me caution you to NOT try firing down with wood to increase the ash glaze. That ash needs lots of heat and time to melt, and if you fire down you will end up with plenty of crusty, unmelted ash glazes, yuk!

I have not fired a wood/gas kiln, but have used propane to preheat overnight before. If you want more ash on the pots, it seems to me you need to stoke wood longer, and use the gas less. Some of the more rich ash glazed surfaces are produced with long firings. We fire the wood kiln here for 72 hours, but it’s a big one and needs that long to fire properly. It’s about 300 cubic feet inside.

So I think you just need to fire longer, and maybe start using the wood at an earlier time.

Bon feu,

Paul Herman

Great Basin Pottery
Doyle California
potterpaul at frontiernet.net

On Feb 25, 2015, at 10:31 AM, Bob Johnson via Clayart <clayart at lists.clayartworld.com> wrote:

> A friend recently built a wood-gas hybrid downdraft kiln, and she is
> learning to fire it. I plan to help her with a firing next week, in return
> for including a few of my own pots.
> Typically, she uses just propane to get the kiln up to 1500 degrees or so,
> then starts stoking with wood, until cone 10 falls. So far she has been
> unhappy with the amount of ash glaze she gets on the pots, so it appears
> that the kiln needs a longer period of wood firing to get better ash
> deposits.
> So, here are the questions:
>   1. Does anyone have experience with a wood-gas kiln? And would you share
>   your firing protocol?
>   2. Any opinions on whether it would it be better to extend the
>   wood-fired soak at cone 10 or to continue to feed wood while firing down?
>   Or some combination of both?
> Thanks!
> Bob
> --in Southern Oregon
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