[Clayart] Flame movers

Terrance Lazaroff via Clayart clayart at lists.clayartworld.com
Wed Feb 18 15:38:17 EST 2015

Could the problems with this kiln be trying to rush the firing?  


Enjoying Spanish sun.

Sent from my iPad

> On Feb 18, 2015, at 7:32 PM, James Miner via Clayart <clayart at lists.clayartworld.com> wrote:
> A bigger problem I have is that the smaller Torchbearer  (23 inch diam) has
> a 3-burner configuration, all in a row, which puts a burner in the center
> of the kiln, necessitating split shelves and putting flame right on the
> center of the ware, producing very uneven heating because all the burners
> are in a line down the middle.  I get a LOT of warping of bowls and cups,
> to the point that I don't make them anymore.  Tried different clays
> (necessitating new glazes as well), but found nothing that solves the
> problem.  Sure, there might be craftsmanship problems, but I think that is
> not the main issue.  I'm thinking of replacing mine with either a larger
> Torchbearer (which would NOT have a center burner), but I'm not sure the
> heating would be much more even.  Perhaps there is some other inexpensive
> downdraft (I am not a professional and cannot really justify $7000+ for a
> "good" kiln).  Any suggestions from the group for a better kiln or a new
> way to look at the problem?
> A used kiln would also be welcome, but they seem to be hard to come by in
> Illinois (I've looked at Craigslist, Ebay, and other on-line resources for
> 2 years).  Anyone know of one?
> Thanks
> Jim
> On Wed, Feb 18, 2015 at 10:28 AM, Snail Scott via Clayart <
> clayart at lists.clayartworld.com> wrote:
>>> On Feb 18, 2015, at 8:29 AM, Deborah Thuman via Clayart wrote:
>>> ...in the Olympic. Cold bottom, hot top...
>> It's a tricky critter, those round Olympics. Not much room (physically or
>> metaphorically) for options.
>> In general: hot on top = damper too wide, up to a point. then it works the
>> other way.  Heat rises when it can, and when the updraft helps it out, it
>> rises a lot, and lurks there at the top like the jam-up at exit after a
>> concert,
>> unless the damper is so open that less heat is actually retained, making
>> the
>> top cold. If it's too hot on top, you gotta retain heat lower down.
>> Tightening
>> the damper is one factor - sometimes it's enough; sometimes it ain't.
>> Setting
>> the shelves wider apart as was suggested, to create an inner gap and close
>> up the one at the sides, is another way to hold the heat down and keep it
>> from sprinting out the top, along with any other modest obstructions.
>> Having
>> a flame that's directed at an angle so it spirals instead of running
>> straight
>> can help, too, if the burner port allows for it. The loading counts for
>> just as
>> much if not more than the shelf stacking. In addition to widening the shelf
>> positions apart from one another to create that inner (split) path, you can
>> use shelf scraps to create slowdowns for the flame even beyond the shelf
>> perimeter. It's all about getting the flame/air to flow where it's needed,
>> at the
>> best speed.  Like training dogs for those agility courses, you can guide,
>> but it works best when what you want dovetails naturally with what it wants
>> to do anyway.
>> In architecture school, we had a course in things like passive solar
>> design,
>> airflow, heat retention, and suchlike. The professor had a concept he
>> scathingly called 'smart arrows' - those authoritative-looking arrows in a
>> drawing of airflow, stating the the air would go here or there, apparently
>> knowing where the architect wanted the air to go rather than obeying any
>> actual laws of physics.  House, kiln...all the same. Want the heat from the
>> floor register to not go straight to the ceiling? Park a table on top of
>> it: a
>> stylish multi-purpose household bagwall...or whatever we wanna call it.
>> Turbulence slows things down: that's what happens when the air path
>> is obstructed, like a quarterback trying to run the ball past the other
>> team's defense, or dodging those perfume demonstrators at the entry of
>> a department store.
>> I'm not a fan of the Olympic gas round. It's an attempt to make inroads
>> into
>> a market niche (gas kilns) at a lower, more accessible price point than
>> most, using the carcase of a product (round electric kilns) that they
>> already manufacture. It can be made to work, but it's not a naturally
>> accommodating design. It's fussy, and it's limited in what you can do
>> with it. You can make it work, but it will take fine-tuning and a very
>> consistent load pattern. No one else's tweaks will work for you the way
>> they do for them, because your load is not the same. And if your own
>> loading varies, so will the firings.
>>            -Snail
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