[sutra]

Hello,
this is my first question to the forum and am hoping for some answers. am doing glazing on stoneware and facing trouble reaching cone5 (1200 deg centrigrade). am not sure if am using the damper effectively. should it be left half open to reach the desired temp.? the temp. rise was happening very slow and had great trouble pushing it up. tried opening the damper to little more than half and the rise in temp did happen but slow...any suggestions on effective use of the damper??

[neilestrick]

Assuming the gas and air are set high enough to reach the desired temperature, and are set at the desired degree of reduction/oxidation, the damper should be set so there is back pressure out both the top and bottom spy holes. One spy hole will have a lot of back pressure, the other will have just a little. Which is which will depend on if you have an updraft or downdraft kiln. All of these variables have to work in unison to get the kiln to do what you want it to do.

[Mark C.]

sutra, on 28 February 2012 - 02:39 PM, said:

Hello,
this is my first question to the forum and am hoping for some answers. am doing glazing on stoneware and facing trouble reaching cone5 (1200 deg centrigrade). am not sure if am using the damper effectively. should it be left half open to reach the desired temp.? the temp. rise was happening very slow and had great trouble pushing it up. tried opening the damper to little more than half and the rise in temp did happen but slow...any suggestions on effective use of the damper??

Leave the damp open al the way till body reduction say around 1800 then push in the damper till you get a little back pressure on lower spy plug-keep checking now and then so this pressure remains-this may mean more damper adjustments-as post above mentions we need to know more about what type of kiln-updraft or downdraft????
The amount the damper is in is all about the reduction back pressure not about 1/2 or any other amount-The temp should climb slowly during this reduction phase till you get whatever cone you need to turn it off-then close damper all the way when off.
Mark

[neilestrick]

I like to stall out the kiln at body reduction for about 45 minutes, then lighten up on the reduction, even go neutral, and let it climb until done. That way I can be sure I get good reduction before the body starts to tighten up.

[bciskepottery]

You might find Nils Lou book, The Art of Firing, helpful on understanding gas firing and how to adjust dampers, etc.

[TJR]

Place a low fire cone with a tiny bowl about an inch long at the base of the cone. Make two of these out of clay. Poke holes in the clay so they don't blow up. Place a cone 012 in both of these little cone packs. Put them in front of your other cone packs which will be cones 4,5 and 6. Your low fire cone packs should face the opposite way as in slanting to the left, then your other cones slant left to right. I would have the damper in half way until body reduction which happens after the 012's are down. Then you push your damper in to one third open. If you get too much back pressure out of your spy holes, pull out the damper slightly. You should have a green flame out of the top spy. If you get a lot of black smoke, your damper is in too far. When you get your damper to where you like it, mark a line with iron oxide on the damper. It will take you a few firings to find what you like.Enjoy!
TJR.
I am speaking about firing a downdraft kiln with gas burners.

[Marcia Selsor]

updraft or downdraft?
Marcia

[Mark C.]

Can we really talk someone thru this on the net ?like talking a non pilot to land a plane
I guess we can try till it crashes.

Mark

[sutra]

bciskepottery, on 29 February 2012 - 06:46 AM, said:

You might find Nils Lou book, The Art of Firing, helpful on understanding gas firing and how to adjust dampers, etc.

yeah, i think i should get one...thanks.

[sutra]

Marcia Selsor, on 29 February 2012 - 07:46 AM, said:

updraft or downdraft?
Marcia

downdraft

[sutra]

TJR, on 29 February 2012 - 07:22 AM, said:

Place a low fire cone with a tiny bowl about an inch long at the base of the cone. Make two of these out of clay. Poke holes in the clay so they don't blow up. Place a cone 012 in both of these little cone packs. Put them in front of your other cone packs which will be cones 4,5 and 6. Your low fire cone packs should face the opposite way as in slanting to the left, then your other cones slant left to right. I would have the damper in half way until body reduction which happens after the 012's are down. Then you push your damper in to one third open. If you get too much back pressure out of your spy holes, pull out the damper slightly. You should have a green flame out of the top spy. If you get a lot of black smoke, your damper is in too far. When you get your damper to where you like it, mark a line with iron oxide on the damper. It will take you a few firings to find what you like.Enjoy!
TJR.
I am speaking about firing a downdraft kiln with gas burners.

Yes, I have a downdraft kiln. Never tried firing using cones. Can you help me understand how to figure out/sense the back pressure. The single spy hole provided in my gas kiln is on the door (front loading kiln) and quite large, almost 3" by 3". Given this size, can I open the spy hole during higher temperatures?

[sutra]

Marcia Selsor, on 29 February 2012 - 07:46 AM, said:

updraft or downdraft?
Marcia

Downdraft, front loading, 2 burners

[neilestrick]

You'll literally have flame coming out the spy holes. The top will have a lot, the bottom will have just a puff. When the entire kiln has pressure inside it means that the reduction atmosphere is getting to all parts of the kiln, and helps it to fire more evenly. You may, of course, have to make adjustments as the kiln gets hotter. Generally the pressure will increase as the kiln gets hotter, and you'll have to open the damper more. Just keep an eye on the bottom spy hole.

Like Marc said, though, this is a tough thing to teach over the net. Is there anyone that can help you in person? Most of this depends on what the kiln is doing, and the settings will change some from firing to firing, depending on how the kiln is loaded, weather, etc.

[TJR]

Mark C., on 28 February 2012 - 08:22 PM, said:

Can we really talk someone thru this on the net ?like talking a non pilot to land a plane
I guess we can try till it crashes.

Mark

I tried. If the guy is up in the air without a parachute, wouldn't you try to talk him down?This is in the spirit of helping.
TJR.

[Marcia Selsor]

[quote name='sutra' date='02 March 2012 - 12:33 PM' timestamp='1330713200' post='14429']

Marcia Selsor, on 29 February 2012 - 07:46 AM, said:

updraft or downdraft?
Marcia

downdraft

[Marcia Selsor]

Start with a gentle flame. do you have a target brick in place?For the body reduction II use cones 09 and 04 with a reservior for their puddles. I place them in front of the 5,6,7 cones.
the cone pack sit inside the peep hole and yesy you should open at high temperature when checking pressure and looking at the cones.
to make the flame harder , increase the air pressure. I fire with the damper more than half shut most of the time. when I get to 09 start reducing by closing the damper a little and cut back on the air pressure.Check for some back pressure from the peephole. At body reduction there usually isn 't that much but the flame should lick in front of the peep hole and may be greenish. usually the greenish purple flame is at the higher glaze reduction. I reduce for 45 minutes then open the damper to about half and turn up both gas and air. you can get a hard flame to bounce off the target brick to get the top hotter. a hard flame has more air. When cone 5 is going start reducing. Again cut the air and shut the damper back a little at a time until the purple greenish flame comes out the peephole and can be seen when you peek in the damper. you can hole a thin stick in this flame and it won't burn due to the lack of oxygen. this indicates reduction. It will flame up when removed from the reduction flame. I reduce for another 45minutes, clear the kiln for 5 minutes and shut it down.
Marcia.

[sutra]

neilestrick, on 03 March 2012 - 01:15 AM, said:

You'll literally have flame coming out the spy holes. The top will have a lot, the bottom will have just a puff. When the entire kiln has pressure inside it means that the reduction atmosphere is getting to all parts of the kiln, and helps it to fire more evenly. You may, of course, have to make adjustments as the kiln gets hotter. Generally the pressure will increase as the kiln gets hotter, and you'll have to open the damper more. Just keep an eye on the bottom spy hole.

Like Marc said, though, this is a tough thing to teach over the net. Is there anyone that can help you in person? Most of this depends on what the kiln is doing, and the settings will change some from firing to firing, depending on how the kiln is loaded, weather, etc.

Thanks Neil for all your suggestions. I am doing one more glaze firing mid April and this time I ve asked a Senior potter from Mumbai to guide me through the firing process...I will keep you all posted on the results...

[sutra]

Marcia Selsor, on 04 March 2012 - 10:16 AM, said:

Start with a gentle flame. do you have a target brick in place?For the body reduction II use cones 09 and 04 with a reservior for their puddles. I place them in front of the 5,6,7 cones.
the cone pack sit inside the peep hole and yesy you should open at high temperature when checking pressure and looking at the cones.
to make the flame harder , increase the air pressure. I fire with the damper more than half shut most of the time. when I get to 09 start reducing by closing the damper a little and cut back on the air pressure.Check for some back pressure from the peephole. At body reduction there usually isn 't that much but the flame should lick in front of the peep hole and may be greenish. usually the greenish purple flame is at the higher glaze reduction. I reduce for 45 minutes then open the damper to about half and turn up both gas and air. you can get a hard flame to bounce off the target brick to get the top hotter. a hard flame has more air. When cone 5 is going start reducing. Again cut the air and shut the damper back a little at a time until the purple greenish flame comes out the peephole and can be seen when you peek in the damper. you can hole a thin stick in this flame and it won't burn due to the lack of oxygen. this indicates reduction. It will flame up when removed from the reduction flame. I reduce for another 45minutes, clear the kiln for 5 minutes and shut it down.
Marcia.

Great...this info should help me great deal, planning a reduction firing (luster glazing) sometime in April...thanks.