[Clayart] fast firing protocol
vpitelka at dtccom.net
Tue Oct 4 16:46:51 EDT 2016
Jonathan Byler wrote:
"I have found that I get my most even firings by pre-heating/candling overnight at about 200-500F with just the pilots and the damper almost all the way in to encourage the gases to stay in and do their job. I run the blowers at a relatively low speed on the main burners (but no gas to them) when pre-heating also to help the heat move around in the kiln. This, combined with the mostly closed damper makes things very even at the start of the firing."
Hi Jonathan -
We have always done a similar overnight preheat, but with the main burners on very low, and the damper closed enough to create a bit of back-pressure. In the morning we crank up the burners and adjust the damper to maintain back-pressure, and we hit body reduction in about an hour with temperatures pretty even. We can finish the firing by mid-afternoon, whereas if we started the firing in the morning we'd still be firing at 6:00. So part of it is convenience, but I also believe that starting cold and cranking the kiln up high is bad for the kiln and will result in quicker structural failure. That may be part of the reason why the 45-cubic-foot IFB downdraft I built almost 23 years ago is still plugging away.
Appalachian Center for Craft
Tennessee Tech University
vpitelka at dtccom.net
From: Clayart [mailto:clayart-bounces at lists.clayartworld.com] On Behalf Of jonathan byler
Sent: Monday, October 3, 2016 4:25 PM
To: Clayart international pottery discussion forum <clayart at lists.clayartworld.com>
Subject: Re: [Clayart] fast firing protocol
I used to do the full blast turn-on procedure, but the kiln climbs between 800 and 1000F an hour for the first hour or so even on a lower setting, so I don’t dump in the heat so fast at the beginning anymore. The kiln also fires more evenly when I’ve started a bit slower. Firings are done in 8-10 hours to ^10, depending on who stacked the kiln, and how much work is in there. I am at 1750F or so when I start reduction with 3-4 hours, and button everything up 5-6 hours later. We got it all done once in 7-1/2 hours, but that is a rarity.
As with Mel, I tend to peak on the gas pressure relatively early in the firing, and am mostly turning it down from there.
Every kiln is a little different, and they all need to be fired the way that works best for that kiln. YMMV. Have fun. Learn something. Have fun learning something, and make more pots!
> On Oct 3, 2016, at 7:56 AM, mel jacobson <melpots2 at VISI.COM> wrote:
> pre heating your kiln to a rather high temp, like 1200F over night
> does nothing for your kiln.
> in fact, it destroys the insulating value of your brick.
> if your kiln is hot on the outside after pre/heat then you have wasted the thermal quality of the brick.
> what i suggest is: use a strong pilot flame and bring your kiln up to
> under 400F over night. (auto shut offs or baso valves are pretty important if you do this.) it will warm your shelves, melt the wax etc. and only the inside face of your kiln is warm. the pots are now warm and ready for firing.
> i turn my kiln to high right off the bat. as i fire, the pressure is turned down. in fact i have almost no gas pressure at cone 11.
> now you have the famous dance. gas pressure, back pressure, damper
> settings for reduction and then a down fire protocol for crystals and copper red.
> each potter will figure out what works for them.
> this system assures you a fine use of fuel, you fire faster without harming your pots or kiln.
> in many cases you will get a color or surface shift...and make sure you chart what you do.
> there are many potters that are using this system with great affect. and, it does save fuel. and if you use blue flame and modest reduction it is even better. color becomes more viable.
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