[Bill R.]

As a self taught potter who has only fired in an electric kiln I have been fortunate to have acquired a small gas kiln (10 cu. ft.) and am very excited about delving into the world of reduction firing. I have researched what I need as far as the basics of firing reduction but am a bit perplexed as this kiln has a computer controller. Not only am I unable to find any information on firing a computer controlled gas kiln but my lack of experience makes it hard to even begin to understand how this will function. Obviously the computer will only operate the burners on this kiln (very basic controller) and reduction will still need my help but how would I establish a firing schedule.

[neilestrick]

The controller probably doesn't operate the burners, either. It functions as a high temp safety shutoff device that opens and closes a gas valve. You'll have to manually control the gas going to the burners. Is there a brand name or model number on the controller? Most gas kilns have controllers that are not made specifically for kilns- they're temperature process controllers used by industry- so you can usually find manuals online. What brand is the kiln?

[Mark C.]

The only gas controller I know anything about is a dd1 on a Geil kiln as a friend has one.You input a temperature say 1,800 and the kiln will at 1,800 turn itself very low and somewhat hold or not surpass this Temp.You control the gas in terms of how much ON (the amount you want to ramp up) you want. You do all the damper controls.
His new kilns now have some reduction (damper controls) I think and you can read about them on his web site.
This is all controlled with valves and a temperature probe.
As you start learning to use this kiln you will still need cones to see what temps/heat work.
On a Glaze I would set this temp to a bisque temp 1st and then reset after getting to that to a temp near your final cone temp. You will want to learn what this shut off probe temp is vs real cone temps are. The only way is use some cones spread around.
What brand is this kiln?
Your controller may not be anything like the one I described.
Mark

[Bill R.]

[quote name='neilestrick' date='09 February 2013 - 08:48 AM' timestamp='1360428531' post='29138']
The controller probably doesn't operate the burners, either. It functions as a high temp safety shutoff device that opens and closes a gas valve. You'll have to manually control the gas going to the burners. Is there a brand name or model number on the controller? Most gas kilns have controllers that are not made specifically for kilns- they're temperature process controllers used by industry- so you can usually find manuals online. What brand is the kiln?

The controller is a "Perfect Fire". The kiln is an "Estrin" made in Vancouver B.C. (no longer in buis.)
There are no manual controls on the kiln except of course dampers. I was able to find a manual for the controller online but there is no info in the manual regarding reduction firing. I have seen these controllers on electric kilns.
I am fairly certain the controller operates the gas valves and I presume you would setup the rate of temp. increase as in an electric kiln but I don't understand how to set up a firing schedule that would incorporate a reduction segment.

[Bill R.]

Mark C., on 09 February 2013 - 10:01 AM, said:

The only gas controller I know anything about is a dd1 on a Geil kiln as a friend has one.You input a temperature say 1,800 and the kiln will at 1,800 turn itself very low and somewhat hold or not surpass this Temp.You control the gas in terms of how much ON (the amount you want to ramp up) you want. You do all the damper controls.
His new kilns now have some reduction (damper controls) I think and you can read about them on his web site.
This is all controlled with valves and a temperature probe.
As you start learning to use this kiln you will still need cones to see what temps/heat work.
On a Glaze I would set this temp to a bisque temp 1st and then reset after getting to that to a temp near your final cone temp. You will want to learn what this shut off probe temp is vs real cone temps are. The only way is use some cones spread around.
What brand is this kiln?
Your controller may not be anything like the one I described.
Mark

Your description of the firing process sounds something like what I was thinking. The controller on this kiln is a "PerfectFire" and I have seen it on electric kilns The kiln itself is locally built by a company called "Estrin". They are well built and were in the buisiness for years before closing their doors aroung 15 years ago. Everybody here in Vancouver knows the Estrin name but I cannot find anyone familiar with this kiln and controller.
I am thinking I will be able to set the ramp up speed to a set temp.(ramp 1 might be to early body reduction) then a second ramp for a glaze firing would take it to the glaze maturation temp. followed by a light reduction and then the controller would shut the kiln off. Something like that ???

[neilestrick]

You'll have to manually set the damper, and possibly the air flow on the burners. Does it have power burners or venturi burners? Most people who fire venturis can get away with just using the damper to control reduction, whereas power burners require adjusting the blower and the damper to achieve reduction.

I'm thinking a possible downside of your controller is that the rate of climb will likely get slower as the kiln gets hotter, so if the controller simply keeps turning up the gas to try and increase temperature, it will affect the atmosphere in the kiln. You'll be at the mercy of the controller. Is this the older model controller that only has a 1 segment program? That could make fore very inefficient firings.

[neilestrick]

Just thought of another option that may work. Put a manual gas valve and pressure gauge before the controller gas valve. Program the controller to run full on, like 2000 degrees per hour, so it has the automatic valve fully open, then control the actual gas flow with the manual valve. Then controller only functions as a high temp safety shutoff, and you can fire the kiln manually.

[Mark C.]

I think Neil said this best what type of burners as this will matter-forced air (blower driven) or venturi natural draft??
This will matter on advice given
for venturi

You just need a ramp schedule you like and you do all the reduction when and how much when you like as well-Think of the controller only as a gas control device.
If its forced air you will need to do some air flow control at fan most likely.
The other thing is call that ceramic supply place in BC ( I have forgotten the name ) they will know this kiln and maybe hook you up with a potter who uses one.
Mark

[Bill R.]

neilestrick, on 09 February 2013 - 11:49 AM, said:

You'll have to manually set the damper, and possibly the air flow on the burners. Does it have power burners or venturi burners? Most people who fire venturis can get away with just using the damper to control reduction, whereas power burners require adjusting the blower and the damper to achieve reduction.

I'm thinking a possible downside of your controller is that the rate of climb will likely get slower as the kiln gets hotter, so if the controller simply keeps turning up the gas to try and increase temperature, it will affect the atmosphere in the kiln. You'll be at the mercy of the controller. Is this the older model controller that only has a 1 segment program? That could make fore very inefficient firings.

The kiln has two venturi burners. The controller is capable of multi segments.
What you mentioned about the rate of temp. climb slowing down makes total sense (even to a rookie like me)
All this helpful insight has really got me thinking. I am thinking there may not be a tremendous advantage to a conputer controller on a gas kiln.
In actual fact it may be a hindrance to someone like me who has never experienced reduction firing and perhaps could learn more by doing things the simple manual way.

[Bill R.]

neilestrick, on 09 February 2013 - 11:52 AM, said:

Just thought of another option that may work. Put a manual gas valve and pressure gauge before the controller gas valve. Program the controller to run full on, like 2000 degrees per hour, so it has the automatic valve fully open, then control the actual gas flow with the manual valve. Then controller only functions as a high temp safety shutoff, and you can fire the kiln manually.

I am starting to think along these same lines.

[Bill R.]

Mark C., on 09 February 2013 - 02:06 PM, said:

I think Neil said this best what type of burners as this will matter-forced air (blower driven) or venturi natural draft??
This will matter on advice given
for venturi

You just need a ramp schedule you like and you do all the reduction when and how much when you like as well-Think of the controller only as a gas control device.
If its forced air you will need to do some air flow control at fan most likely.
The other thing is call that ceramic supply place in BC ( I have forgotten the name ) they will know this kiln and maybe hook you up with a potter who uses one.
Mark

As I responded to Neil, I have venturi burners so that makes it a bit less compicated.
As far as a ramp schedule do you have any suggestions. I have zero experience with gas reduction firing so even creating a schedule is a bit of guesswork on my part.

[Mark C.]

In my 35 cubic car kiln I usually get up to 1800 in about 6-7 hours or so then I fire the rest of the way to soft cone 11 in reduction. I start a bit earlier if I have reds in the fire.
I fire all loads of porcelain in reduction.
I took Nels Lou advice years ago about firing as fast in the early stages as the furniture can take as the thermo mass soaks up the BTUs if you let it. I go slower till red heat then let it fly.A typical glaze fire is 12-14 hours
Mark

[Bill R.]

Mark C., on 09 February 2013 - 04:29 PM, said:

In my 35 cubic car kiln I usually get up to 1800 in about 6-7 hours or so then I fire the rest of the way to soft cone 11 in reduction. I start a bit earlier if I have reds in the fire.
I fire all loads of porcelain in reduction.
I took Nels Lou advice years ago about firing as fast in the early stages as the furniture can take as the thermo mass soaks up the BTUs if you let it. I go slower till red heat then let it fly.A typical glaze fire is 12-14 hours
Mark

Based on your firings what do you think of a firing schedule like this
ramp 1 - 150 deg./hr to 300deg
ramp 2 - 300 deg./hr to 1800 Hold for 1 hour, put the kiln in heavy reduction
ramp 3 - 100 deg./hr to C10 with kiln in light reduction

[Mark C.]

Bill R., on 09 February 2013 - 07:50 PM, said:

Mark C., on 09 February 2013 - 04:29 PM, said:

In my 35 cubic car kiln I usually get up to 1800 in about 6-7 hours or so then I fire the rest of the way to soft cone 11 in reduction. I start a bit earlier if I have reds in the fire.
I fire all loads of porcelain in reduction.
I took Nels Lou advice years ago about firing as fast in the early stages as the furniture can take as the thermo mass soaks up the BTUs if you let it. I go slower till red heat then let it fly.A typical glaze fire is 12-14 hours
Mark

Based on your firings what do you think of a firing schedule like this
ramp 1 - 150 deg./hr to 300deg
ramp 2 - 300 deg./hr to 1800 Hold for 1 hour, put the kiln in heavy reduction
ramp 3 - 100 deg./hr to C10 with kiln in light reduction

I am assuming you are firing stoneware?

I would not hold it at 1800 and not do Heavy reduction but if its stoneware and you want some claybody color you will need to be a little heavier for say 1/2 hour then ramp
it at least 150 per hour
Remember the reduction will slow it down no matter what you dial in on ramp speed-reduction slows the fire down
use cones to see what the probe says when you reach your final cone temp then shut it off
next fire you can set it near that temp-so you will need to be there to watch the cones fall
Did you consider calling that supply hose in BC for tips on this unit?
Mark

[Bill R.]

I will definately call them. It's a 3 day weekend here in B.C. so they have shut-er-down for the holiday.

I am firing stoneware and I will heed your advice regarding hold and reduction. I think the slow rate of climb from 1800 up will work with the controller. Neil's idea about installing a manual valve and pressure gauge before the controller valve might be a good one just in case.
I love the excitement and challenge of trying something new. I just fret a bit over experimenting with a kiln load of pots that I worked so hard to create. But I am already feeling more confident after all the advice I am getting. I will definately watch the first firing closely.

[Mark C.]

One thing to always remember is they all can be made again if they get messed up in the fire-
Mark

[neilestrick]

When I fire reduction, I always stall the kiln for about 45 minutes at cone 012 (or whenever you choose to reduce). This guarantees that I get good reduction throughout the kiln before the temp gets too high and prevents good reduction. Then I fire in light reduction to neutral atmosphere up to cone 11, then stall out in oxidation for about 15 minutes at the end. Lots of different ways to fire.....

[Marcia Selsor]

When I fire reduction I always reduce for body reductio between 09-04. Anyone else do that?
Nils is a great person to get advice for kilns. '

Marcia