How did you learn to fire your own kiln?

[High Bridge Pottery]

@tomhumf You can get away with using wet clay and making cone packs that don't blow up. I make a long thin (0.5-1cm) sausage of clay then hold/balance the cones on something flat and squish the sausage around them so it only holds at the sides, bottom of the cones sit on the shelf. Poke lots of holes. Never had one blow up. 

 

[Pres]

I started using handle extrusions to make cone packs, think I will design a cone pack die, and make a bunch at once.

 

best,

Pres

[Mark C.]

I just make them in bulk and put on heater in shop-always have a dry one.Make about 10 at a time-I use two every other week.

If you are last minute just add vermiculite as noted by another poster and poke holes in clay and make the pack very small and use a hand torch to dry-see how easy last minute is time wise???The last thing is if the pads is wet you have to fire SLOWLY until over 800 degrees.

[Housefull of pots]

On 10/18/2018 at 10:37 PM, Babs said:

Portokiln...you in Australia?

Search John Eagle a Victorian potter.

He wrote an article in Pottery in Australia  but now named "the journal of Australian Ceramics" on reduction firing.

He gets beautiful colour variances with reoxidation towards end of firing, blushes instead of the ubiquitous red and gets beautiful colours by Appling washes over the glazes he uses.

You may get insight from this potter on his firing schedules.

Hi Babs,

 

Thank you for your reply.. no I am in Cornwall, UK =)  My little port-o-kiln must be over 40 years young I reckon and it's a mystery as to how she got here,  it's in good nick and has probably passed through may hands. Thankyou for the tip re John Eagles,  very interesting man and work. I can't find the specific article you recommend but will have another look another day just in case I can unearth it. 

S

[Housefull of pots]

On 10/18/2018 at 11:07 PM, High Bridge Pottery said:

The best way to learn is to fire it  Seems like you had a good start as you already worked out less gas can be more heat. When it's real hot is the best time. I think the splintering noise you can hear is fine, not sure it is the pots. 

Think the splintering noise was fine whatever it was as the pots came out pretty well. I have some black clay that I am trying to find the correct firing temp for with a few glazes I have made up. The small plates I have made on the lowest shelves have all melted but the cups were all fine.. I think it must be something about how I have made the plates.  I think soaking will improve the next firing to even out the heat as there is a big discrepancy between the top and bottom of the kiln. Thanks for the encouragement, I feel like i am picking things up all the time =-)

[Housefull of pots]

On 10/18/2018 at 11:23 PM, Patrick said:

+1 on learn by doing. See what works and do that again.  See what doesn't work and don't do that again/make adjustments to your kiln.  The largest problems I have had with gas kilns I fashioned was stalling them out before target temp because my exit hole(s) were too small. Rather have too large of an exit flue you can close down than one that's "just the right size" based on head scratching. (+1 what Neil said.) Congrats!

Regrading hoods/vents. I've just used HVAC ducting, sheet metal, snips, rivets.  The photo will give you an idea.   Not ideal, but it's cheap and  works to get majority of the hot air out of my 100 year old wooden garage. The metal gets hot enough to screw up the galvanized finish (which is probably toxic by some measure) but that's about it.

THanks Patrick =-)

Good to see pics and hear of home made kilns pros and cons.. love the glass of red you had to put down to take the pic lol.  The hood worked fine, maybe could have been a bit wider actally as it was getting pretty hot and the finish kind of shmooshed like you said but otherwise pretty happy. I found a manual online which described how to make a hood with dimensions and it pretty much matched up what we came up with so that was cool.  Gonna do another firing this week hopefully and test out top temps with some ash glazes. 

S 

[Housefull of pots]

On 10/23/2018 at 9:57 PM, tomhumf said:

I've recently converted an electric kiln to gas.

Today I started firing it with cone packs I made the previous night. I had put holes holes in them, and they seemed pretty dry. Lucking after about an hour I looked in my burner port and saw debris in the bottom of kiln. Both my cone packs had exploded. I had to shut it off, wait until it cooled and brush off clay fragments from all my ware, and repack the whole thing. I've now made a load of cone packs that will be dry well before I need them. 

Last firing I had a load of dinner plates to bisque. I has struggled to get a low enough flame when candling the kiln. And after about 1 minute the rim of one of the plates near the flame path exploded. I pulled the flame back and continued thinking the rest were ok. I will be more careful, and keep large plates away from flames in future.

I had stacked 6 plates in pairs on shelves with sand between them, to save on kiln space. Two plates were on shelves of their own because I was worried this might end badly.  I do stack bowls with sand without problems. When I unloaded the kiln, all the stacked plates were cracked to bits, the plates on their own shelves were fine. So I won't stack plates like that again, I need to buy some more props and shelves. 

This probably doesn't help you at all, but is a reminder to me not to do stupid stuff again. Whatever you do, there will be mistakes. You've just got to learn from them. 

Ouch.  There are literally so many elemts to the making, glazing and firing process that can go up. Good luck for the next batch!

[Housefull of pots]

On 10/25/2018 at 2:42 PM, High Bridge Pottery said:

@tomhumf You can get away with using wet clay and making cone packs that don't blow up. I make a long thin (0.5-1cm) sausage of clay then hold/balance the cones on something flat and squish the sausage around them so it only holds at the sides, bottom of the cones sit on the shelf. Poke lots of holes. Never had one blow up. 

 

.. On this note @High Bridge Pottery - Excuse my ignorance - How are you supposed to see when the cones have gone?  I opened up the spyhole but the heat is so blinding - do you use some special dark goggles or something>??

[Mark C.]

Yes you need the right glasses-the ones wielders use to protect your eyes from the infrared heat rays. Get a #4 welding glass to view cones. Do nit use your eyes unprotected .

[Rex Johnson]

Yes you need welders or other infrared googles (green lens) when peering into ports or you'' end up like me having welder's cataracts at 50 years old...

I never wore correct lenses learning glassblowing nor firing kilns. Duh.

[Chilly]

And you need 

On 10/28/2018 at 11:18 PM, Housefull of pots said:

.. On this note @High Bridge Pottery - Excuse my ignorance - How are you supposed to see when the cones have gone?  I opened up the spyhole but the heat is so blinding - do you use some special dark goggles or something>??

And you need to line the cones up so they are silhouetted against an element, with a clear view across from the spyhole.  Tricky to set up, and MUST use welders goggles.

[Bill Kielb]

I will add something here. If you can master the combustion efficiency part of gas flames and you become aware of the actual combustion theory, things become very easy and intuitive. I was fortunate to teach combustion for twenty years and to potters the thermodynamics are a bit overwhelming not to mention boring. Most gas fired kilns eventually heat through radiation and conduction as convection becomes a smaller and smaller part of the equation. Unfortunately we need that correct mix of air and gas to get the most efficiency from our flame to generate the heating required. This likely sounds daunting but I assure you it really is not.

At our studio I just spent a year helping a group test and build these skills and a reduction firing schedule that saves gas but reduces better. The project was a success and they will now continue to further reduce their carbon footprint while getting great results. The project was so successful that they decided to share the schedule with the art community. Your post has inspired me to devise an easy way for folks to understand this.  Give me a month or so and we will share a simple video on how this stuff works.  I've attached their reduction schedule here and expect to put up the video on the Madison Pottery You tube channel which we envision as a place to share information.

[Housefull of pots]

On 11/15/2018 at 6:25 AM, Bill Kielb said:

I will add something here. If you can master the combustion efficiency part of gas flames and you become aware of the actual combustion theory, things become very easy and intuitive. I was fortunate to teach combustion for twenty years and to potters the thermodynamics are a bit overwhelming not to mention boring. Most gas fired kilns eventually heat through radiation and conduction as convection becomes a smaller and smaller part of the equation. Unfortunately we need that correct mix of air and gas to get the most efficiency from our flame to generate the heating required. This likely sounds daunting but I assure you it really is not.

At our studio I just spent a year helping a group test and build these skills and a reduction firing schedule that saves gas but reduces better. The project was a success and they will now continue to further reduce their carbon footprint while getting great results. The project was so successful that they decided to share the schedule with the art community. Your post has inspired me to devise an easy way for folks to understand this.  Give me a month or so and we will share a simple video on how this stuff works.  I've attached their reduction schedule here and expect to put up the video on the Madison Pottery You tube channel which we envision as a place to share information.

Hi Bill,

Thanks for sharing your groups test results, looks very accurate and scientific, but I can read the general firing schedule without knowing the measurements of oxygen etc. Is this chart recording a firing of cone 10 in 5.5 hours? How did they achieve the fast rate of the last hour? I am firing again tomorrow, quite excited. (But have forgotten to buy cones which is a bit annoying!)

[Bill Kielb]

On 11/30/2018 at 7:02 PM, Housefull of pots said:

Hi Bill,

Thanks for sharing your groups test results, looks very accurate and scientific, but I can read the general firing schedule without knowing the measurements of oxygen etc. Is this chart recording a firing of cone 10 in 5.5 hours? How did they achieve the fast rate of the last hour? I am firing again tomorrow, quite excited. (But have forgotten to buy cones which is a bit annoying!)

Thanks,

The firing  ends up to be cone 10 in just over eight hours.  They begin to candle (pilots only, minimum blower speed)  at 7:30 am and leave before five. If we let them candle overnight they would probably knock an hour or more off so  easily could be maybe 7 hours. They  have the benefit of some custom monitor equipment that allows them to dial in their rate. I’ve atttached a recent spreadsheet showing just over 8 hrs from room temp to cone 10.

There is a quick reduction 101 video that details the how and why part of their tested schedule on the Madison Pottery you tube channel ( among other self help videos). It is a channel that we recently started to share misc.  pottery  techniques, repairs, etc....as they are discovered or requested.

 

 I believe the video details the results of this firing as well with respect to reduction and carbon trapping. Nice wares! Great group of artists and consistent good results. Great group for sharing, inspirational actually.

Just to add, they do not go very fast towards the end, instead they rely on  keeping reasonable pace throughout the early firing and finish fairly slowly. They are working on bringing the reduction levels down to save more gas and believe that they will get clearer reduced reds in so doing. If they succeed in lowering their levels later in the firing without affecting their desired result they will increase their end firing speed considerably. So far It looks like 0.65 at the end will be fine with better results and much greater speed.

Since this is a group (community) they must all agree on the firing intent prior so changing (reducing) this final reduction level is going a bit slow as you might imagine.

 

 

 

[Bill Kielb]

On 10/28/2018 at 6:18 PM, Housefull of pots said:

.. On this note @High Bridge Pottery - Excuse my ignorance - How are you supposed to see when the cones have gone?  I opened up the spyhole but the heat is so blinding - do you use some special dark goggles or something>??

Sorry just started reading these …. my bad! Correct Infrared glasses here please and for heavy reduction green dot laser that you can spread the focus out to be more of a spot. Works great but don't forget your proper eyewear! The laser lights up the cones and they appear bright white and glossy ……… with your eye protection on. Also have a quick video o the Madison Pottery you tube channel if you want to watch.

 

 

[Bill Kielb]

On 10/28/2018 at 6:05 PM, Housefull of pots said:

THanks Patrick =-)

Good to see pics and hear of home made kilns pros and cons.. love the glass of red you had to put down to take the pic lol.  The hood worked fine, maybe could have been a bit wider actally as it was getting pretty hot and the finish kind of shmooshed like you said but otherwise pretty happy. I found a manual online which described how to make a hood with dimensions and it pretty much matched up what we came up with so that was cool.  Gonna do another firing this week hopefully and test out top temps with some ash glazes. 

S 

Nice Work! When we design natural draft hoods we usually rely on temperature difference to move the correct amount of air up the stack. This sounds complicated but where I usually see folks have difficulty with reduction firing is by not having the hood spaced far enough above the kiln.  All things being equal more spacing is better. The design part is actually limiting the interior chimney temperature to 500 degrees while maintaining enough velocity to scrub the moisture from the pipe walls. Most folks make the mistake of too large of a pipe and too slow a velocity.

Your setup is fine, raise it above the kiln if necessary, damper at the top of the kiln to control your firing and change the size of the flue pipe as you observe operation and desire more or less velocity to preserve the pipe. Just a note, an atmospheric hood design and double wall B vent is generally for Natural gas fuels. No wood or oil or other.  This kiln appears to be outside in adequate free air. Once you move something like this indoors it really needs to be designed by knowledgeable folks to be reasonably safe. 

 

[neilestrick]

16 hours ago, Bill Kielb said:

Since this is a group (community) they must all agree on the firing intent prior so changing (reducing) this final reduction level is going a bit slow as you might imagine.

Bill brings up a good point here. How you fire is all dependent on what your goals are. Different glazes and different clay bodies all have different firing requirements to get a certain result. A firing schedule that benefits one glaze may not benefit another.