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ayjay

Firing down

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I've finally replaced my old kiln, (it was a bit on the small side and only had a top temp of 1200°C).

 

My new (to me ) kiln is larger and will go to 1300° which obviously gives me more options with glazing, most importantly I can now fire properly to cone 6 (it's the new cone 10).;)

 

A lot of what I've read recently (particularly in MC6) suggests that firing down is important, the controller with the new kiln is a Stafford ST301, it's a fairly simple controller and has two programmable ramps for firing to the required temperature but doesn't appear have any means of firing down.

 

Is there any way to do this by reprogramming after firing is finished?

 

I wondered about putting in a programme after temperature is reached and the soak is finished to fire to maybe 800° and hold for a while, or even setting ramp two to a lower temperature than ramp one.

 

Can I input a minus figure for the temperature increase?

 

Does anyone understand any of that? :D

 

It's not wired up yet, I'm waiting for a sparks to get some free time, so being unable to test any of my theories I thought I'd ask first.

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I THINK I understand where you're at.

 

My glaze firing scheduule has 5 ramps or rates to it, the 1st 3 are heating up to top temp, the next 2 are cooling down. If ramp 3 is ?????/perhour to top temp, then enter ramp 4, and a degree rate, and a temp that is lower than peak and it will drop in a controlled manner, maintaining the slower drop that you programed in. You don't need -numbers, just lower temps, the kin will understand what you mean.B)

 

My ramp 4 is 500*/hour to 1800*, hold 30 minutes, like in Mastering ^6 Glazes. then another ramp, #5, with a rate of drop and an even lower temp. the computer controlles the drop, giving controlled cooling.

 

the kiln may not cut on very often during these dropping temps just enough to controll the cooling and not have a rapid cool down.

Hope this helps.

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I fire down manually at 150 f. per hour between 1900 and 1500. It really made a difference with my floating glazes. My cone 6 stuff looks as good as the cone 10 reduction stuff I do at work. It seems I've heard that it won't make as much difference with glassier glazes, but that it really helps with matt glazes. I've found it to be a great help, if that affirmation is helpful to you. But, I can't help in programming your machine.

 

Joel.

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Many thanks for taking the time to reply, I'm thinking I may just have to have a play around when the new electricity supply has been fixed up.

 

 

My glaze firing scheduule has 5 ramps or rates to it, the 1st 3 are heating up to top temp, the next 2 are cooling down.

 

 

I don't have that option, hence the query about re-programming (using only the two available upward ramps) after top temperature is reached.

 

 

I can tell you from experience that it is very hard to catch the temperature drop and program after firing stops ... If your programmable part has at least 5 steps you can do it as clay lover says.

 

 

I don't see any problem in seeing when firing is finished, I'm always around when the kiln is on, and even if I'm not in the same space I have a wireless monitor displaying all of my electric usage which will show me when the kiln is no longer using any electricity, but I only have two programmable ramps, both upward as far as I know.

 

I fire down manually at 150 f. per hour between 1900 and 1500. It really made a difference with my floating glazes.

 

Joel.

 

 

Can you explain just a little more about how you manually fire down, I'm unable to work out how I would do this with either the old kiln or the newer kiln. The controllers are a Bentrup TC 20 and a Stafford ST301

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I've finally replaced my old kiln, (it was a bit on the small side and only had a top temp of 1200°C).

 

My new (to me ) kiln is larger and will go to 1300° which obviously gives me more options with glazing, most importantly I can now fire properly to cone 6 (it's the new cone 10).;)

 

A lot of what I've read recently (particularly in MC6) suggests that firing down is important, the controller with the new kiln is a Stafford ST301, it's a fairly simple controller and has two programmable ramps for firing to the required temperature but doesn't appear have any means of firing down.

 

Is there any way to do this by reprogramming after firing is finished?

 

I wondered about putting in a programme after temperature is reached and the soak is finished to fire to maybe 800° and hold for a while, or even setting ramp two to a lower temperature than ramp one.

 

Can I input a minus figure for the temperature increase?

 

Does anyone understand any of that? :D

 

It's not wired up yet, I'm waiting for a sparks to get some free time, so being unable to test any of my theories I thought I'd ask first.

 

 

For some glazes I use a fire-down program, but learned a few years ago that a complicated fire-down is never necessary and often no fire-down is needed at all. I was getting ready for a show and needed to fire pots in my computerized kiln that I had set up with a very complicated ramp up and down. I had already fired two loads in it and was very happy with the glazes. But that kiln suddenly malfunctioned (none of the middle switches worked) and I didn't have time to get the parts and fix it so I fired that last load in another kiln that didn't have a computer. I decided that instead of standing there in the wee hours of the morning manually firing it down, that I'd just fire one cone hotter. I knew it wasn't the same as a controlled cool down but heat-work is still heat-work and the over-firing would at least give it more of that. To my great joy that last firing was just as good as the other two. So now, I fire most of my glazes one cone hotter because only a few need more of a slowed cool down and that one is very simple. My point is this: Often a fire-down is not needed and when it is needed it doesn't have to be a very complicated one.

 

Jim

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So now, I fire most of my glazes one cone hotter because only a few need more of a slowed cool down and that one is very simple. My point is this: Often a fire-down is not needed and when it is needed it doesn't have to be a very complicated one.

 

 

Voice of experience there. Good stuff.

 

The really important point I see in your posting there Jim, is that there is no such thing as "one size fits all" firing. I've been pounding that idea hard in my classes and written materials since the 70's. Firing is based upon the SPECIFIC clay and glazes in the kiln and the SPECIFIC results that you want to get out of them. So HOW you fire (firing cycle) is based upon that knowledge and (likely) on doing a lot of testing to GET them to work well. What works for one situation does not necessarily work for another.

 

For one simple example, SOME people might want Glaze A to develop more micro-crystalline growth

within the glassy matrix... but others might NOT want that to happen with that same Glaze A. For one person it is a "feature" ... for another it is a "defect".

 

Nothing takes the place of putting in the dues to LEARN about your materials and how to use them well. Forums, books, videos, classes and such can point you in the good directions........ but HARD WORK in the studio is what gets you "there".

 

best,

 

..................john

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Can you explain just a little more about how you manually fire down, I'm unable to work out how I would do this with either the old kiln or the newer kiln. The controllers are a Bentrup TC 20 and a Stafford ST301

 

 

I will admit that it is a huge pain. The problem is that when you reduce the heat settings, the kiln will cool at a geometrically diminishing rate; so it may be @ 2.5/min. initially, but after 50 deg. it may drop to 1.9/min. then in another 50 deg. maybe to 1.1 deg (somewhat idealized example). Ultimately I end up bouncing around for between 2 and 3 hours. Granting I don't actually know anyone who does a lot of cone 6 stuff, it remains that by using downfiring I get much more depth out of my work than anyone I know doing cone 6 locally. That being said, I've been pretty obsessive about application thickness too. My cone 6 stuff looks just as good as the cone 10 stuff we fire at work.

 

A lot goes into a good glaze firing and I'm no expert. I simply go on the presumed fact that crystals grow better with a certain negative rate-of-rise in a certain temperature range. This is surprisingly complex stuff, at first at least, unless you have someone nearby to learn rote from. I'm working out of, Mastering Cone 6 Glazes. It is serving me well. I believe that it has allowed me to skip through years of correcting bad information that applied to only a few glazes being fired in a particular kiln. It provides good general information, and that is, in my opinion, the most valuable stuff to be had. Call me headstrong, but I insist on filling in the particulars myself, :)

 

Addendum: The guy you need to talk to is Neil, he's the kiln guy. You might also post a pic of your controller or a link to a pdf manual. Intuitively, the first thing that pops into my head, is to let the kiln fire through its firing cycle, then let it drop past 1900 (or your preferred start point), about 50 deg. then turn it on and let it rise 25, turn it off, let it drop 50, turn it on, and so on. Just keep a record and chart the real downward slope and try to take 2-3 hours to get to 1500. It's time consuming, and [edit: oops, Jim, sorry] suggests it isn't necessary, but it may be worth exploring if you are using matte glazes or boron frits. PS, I over-fire about a half a cone too.

 

 

gallery_10453_418_1557543.jpg

 

 

Joel.

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You say your new kiln fires to 1300 degrees--I'm assuming you meant 2300 degrees, right? 'Cause if what you wrote is true, you'll not make it to cone 6.

 

I was assuming he was talking about 1300 Celsius.

 

best,

 

....................john

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For some glazes I use a fire-down program, but learned a few years ago that a complicated fire-down is never necessary and often no fire-down is needed at all............................ So now, I fire most of my glazes one cone hotter because only a few need more of a slowed cool down and that one is very simple. My point is this: Often a fire-down is not needed and when it is needed it doesn't have to be a very complicated one.

 

Jim

 

 

I will keep this in mind and do my first fire in this kiln with no playing around.

 

 

 

The really important point I see in your posting there Jim, is that there is no such thing as "one size fits all" firing. I've been pounding that idea hard in my classes and written materials since the 70's. Firing is based upon the SPECIFIC clay and glazes in the kiln and the SPECIFIC results that you want to get out of them. So HOW you fire (firing cycle) is based upon that knowledge and (likely) on doing a lot of testing to GET them to work well. What works for one situation does not necessarily work for another.

 

 

 

Nothing takes the place of putting in the dues to LEARN about your materials and how to use them well. Forums, books, videos, classes and such can point you in the good directions........ but HARD WORK in the studio is what gets you "there".

 

best,

 

..................john

 

 

I'm always trying to learn, but it takes longer to sink in and remain there these days, wish I'd started 50 years earlier.

 

I understand about getting to know the specifics required for each clay/glaze/kiln/fir combination, but a problem arises with the lack of output of a hobby potter, I'm not at it 40-50+ hours per week, it takes time to accumulate all the knowledge borne of experience - and so we look for short-cuts.

 

Intuitively, the first thing that pops into my head, is to let the kiln fire through its firing cycle, then let it drop past 1900 (or your preferred start point), about 50 deg. then turn it on and let it rise 25, turn it off, let it drop 50, turn it on, and so on. Just keep a record and chart the real downward slope and try to take 2-3 hours to get to 1500. It's time consuming, and [edit: oops, Jim, sorry] suggests it isn't necessary, but it may be worth exploring if you are using matte glazes or boron frits. PS, I over-fire about a half a cone too.

 

 

gallery_10453_418_1557543.jpg

 

 

Joel.

 

 

That's pretty much what I had in mind, although I've tried it on my old kiln and it wouldn't re-start, I just got an error code. It is the matte glazes I'm thinking of, they do so often please me more than a really glossy glaze, but I'll see how it goes first, there's still plenty of room on the discard heap.

 

Nice job with the Waterfall Brown.

 

Okay, I'm assuming something here, just want to know it's true. You say your new kiln fires to 1300 degrees--I'm assuming you meant 2300 degrees, right? 'Cause if what you wrote is true, you'll not make it to cone 6.

 

 

You're cherry picking, the previous line said the old kiln goes to 1200°C, I thought that set the parameters, or maybe I just missed out a C, it looked OK when I read it through.;)

 

Thanks again to everyone for their help, it is much appreciated.

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I understand about getting to know the specifics required for each clay/glaze/kiln/fir combination, but a problem arises with the lack of output of a hobby potter, I'm not at it 40-50+ hours per week, it takes time to accumulate all the knowledge borne of experience - and so we look for short-cuts.

Amen to that. I'm working out of my shop only every so often. I do pottery as a profession at work, but I'm pretty much limited to throwing production and waxing/glazing. I often never see my finished work. Almost all of my glaze training is done at home and I read and fire when I can (about once every one or two months). It is very difficult to keep one's thoughts ordered. All I can suggest is to keep records and keep samples of your work so you can compare like to like.

Joel.

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Along these lines...

 

 

I don't like to quick drop in temp when the firing is complete.

 

What I think I'll do is to shut off the vent after the temp drops below 2000F (temp reconmended by the vent manufacturer) after the ^6 firing to slow things down a bit.

 

Anyone else shut off their vent in this manner?

 

 

Thanks.

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Yedrow, good looking Waterfall.

 

I, too , am a ^6 potter, working with MC6G glazes as well. I get good looking deep, complex surfaces and great satin matts. Not many people around here down fire, but I think it is a major reason my glazes look good.

 

I am having some trouble with slight pitting and cheezy surface. More with speckled clays , but some also from white clay bodies. I drop from peak temp to 1900* at 500 * per hour like the book suggestes, but am wondering if that is to quick for that glaze. Don't pits come from cooling too fast before that bubbles can heal over?

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Yedrow, good looking Waterfall.

 

I, too , am a ^6 potter, working with MC6G glazes as well. I get good looking deep, complex surfaces and great satin matts. Not many people around here down fire, but I think it is a major reason my glazes look good.

 

I am having some trouble with slight pitting and cheezy surface. More with speckled clays , but some also from white clay bodies. I drop from peak temp to 1900* at 500 * per hour like the book suggestes, but am wondering if that is to quick for that glaze. Don't pits come from cooling too fast before that bubbles can heal over?

 

Bubbles should heal over before cooling begins. Some glazes just do better with slower everything.

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Yedrow, good looking Waterfall.

 

I, too , am a ^6 potter, working with MC6G glazes as well. I get good looking deep, complex surfaces and great satin matts. Not many people around here down fire, but I think it is a major reason my glazes look good.

 

I am having some trouble with slight pitting and cheezy surface. More with speckled clays , but some also from white clay bodies. I drop from peak temp to 1900* at 500 * per hour like the book suggestes, but am wondering if that is to quick for that glaze. Don't pits come from cooling too fast before that bubbles can heal over?

 

 

I fire pretty much the same way you described. I soak for about 10 to 20 minutes, depending on where the 7 cone is. I don't have any problem with pinholing or pitting, but I only use three dark clays and one white body. I know the glaze is 'frothing' around peak temp. but that goes away as it cools. I drop temp at or under 500/hour. I would slow that down were I problem solving the issue, but there are much better glaze people than me here for you to get suggestions from.

 

Joel.

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