How can I single fire to cone 6?

[Kakes]

Hi all,

Newbie here! Although I've been working with clay for several years, I'm new to doing my own firing. I recently acquired a new kiln & it's been a huge learning curve. I would like to try single firing my pieces to cone 6. I will not be glazing for the most part - just oxide wash or terra sig.  Most of my pieces are slab constructed, some horizontal and some vertical, fairly large. Could someone recommend a firing schedule for this? For an electric kiln? (I'm still learning how to program my own ramp/hold program). Thank you!

[dhPotter]

Look up Steven Hill.

Here is my single fire schedule. The schedule handles pinhole issues and allows crystals to grow. Been single firing for 2 years. Never looked back to doing bisque. Some people glaze when their pots are hard leather hard. I wait till completely dry. I spray glazes normally but dip test tiles. Good Luck.

Kiln - Olympic 2327 HE

Glaze cone 6...

Segment    Rate F*/HR   Temp   Hold

   1                       200              220     30-60

   2                       100              500       0

   3                       400              2050      0

   4                       108              2185^  15

   5                      9999             2085     20

   6                      9999             1700      0

   7                        50               1600    60

   8                        50               1500      0

[Kakes]

Thank you so much, dhPotter, I will try it. If I'm reading this correctly, the target temperature is 2185, right? Is that lower than the usual cone 6 firing?

I read Steven Hill's articles which were helpful but couldn't find an actual schedule. 

[liambesaw]

There's a 15 minute hold there which is usually enough to drop a #6 cone (or close enough).  That's where the "heatwork vs. temperature" comes in.

[Chris Throws Pots]

2185 with a 15 minute hold should get you to 6 in a way that'll allow you to get into your controlled cooling segments of the firing while limiting the risk of glazes running all over the place at peak.  But you should include cones in your firing to inform how best to adjust top temp if the program doesn't get you to 6.

[dhPotter]

Steven Hill's ^6 firing schedule is here ---> https://ceramicartsnetwork.org/daily/firing-techniques/electric-kiln-firing/glazing-and-firing-techniques-atmospheric-like-effects-in-an-electric-kiln/

Yes the cone is a perfect ^6 according to Orton for SSB cones. My kiln is cooler for the top shelf by about 1/2 cone. But this doesn't seem to affect the glazes on the top shelf. The kiln has a single TC only. I always have 3 cones on each shelf for every firing. I was firing to 2195 with the 15 minute  hold and this proved too hot for the Laguna 609 clay. Would occasionally get bloat, which seemed to be happening more often. That is why the 2185 top temp. Interesting, when I first started firing my own kiln 10 years ago, 2185 was the top temp then and was till about 2 years ago. I have no idea why I went to 2195, maybe to see if the grass was greener with more heat?

[Kakes]

Thanks for the link, dhPotter. Am I understanding correctly that segment 5 begins the cool down? I'm confused by the "9999". Sorry, this is all     new to me.

[liambesaw]

The 9999 is the rate at which it is heating or cooling per hour.  Basically on the way up, it's "high" setting, on the way down it's a natural cool (instead of controlled)

[nancylee]

I took a workshop with Steven Hill and single firing worked great with his glazes, but when I tried to do it with commercial glazes, everything came out with pinholes, or “lumpy,” just horrible. Ugh. I followed his schedule, so maybe a different schedule may have worked.

nancy

[dhPotter]

these 2 segments are imperative to no pinholes...IMO...both recommended by potters on this forum. Has worked very well for me. My clay is Laguna 609.

  4                       108              2185^  15

   5                      9999             2085     20

The 9999 tells the controller to free fall cool.

[Stephen]

What is the advantage of single fire and is it worth the risk of handling greenware? I would be worried about damage going undetected and produce a flawed pot. Dry un-fired clay just does not seem sturdy enough to me that I could trust my process. 

[dhPotter]

The hardest part for me was to remember to have completely dry hands when handling greenware while glazing. It took me about 5 kiln loads of spraying glaze to figure out the thickness of glaze to properly apply and to figure out the proper Specific Gravity. Closed forms, mugs and pitchers, have the interior poured then spray all of these vessels upside down on a pedestal. This helps to keep overspray out the interior. Bowls are sprayed upside down to spray the outside then flipped over to spray the interiors. Take a look at my gallery and you will see all sorts of forms being sprayed and so they are being handled much like you would bisque. It is time consuming to spray. The need for equipment is a drawback. OldLady sprays outside, but this also has its limitations. The Critter sprayer is cheap and I have 3 of them. I usually use at least 3 glazes to finish a piece. I bought a dozen plastic pint jars that fit the Critter perfectly. This allows for multiple glazes to be ready for the sprayer. The air compressor is an 8 gallon, 125 psi from Harbor Freight. The Critter likes 40 psi.

Stephen I may not have answered your question, but maybe I have. I did not find it difficult to use greenware. The worse happening was I broke the cup off a goblet stem, but it was poorly attached and used spooze to fix it. Then when I was pouring the liner I completely forgot this piece was the previously broken piece after the pour was finished. 

Steven Hill say single firing keeps him engaged with his work because he doesn't have the down time involved with a bisque firing. I do it to cut out a process that, to me, is not really needed and my time in the studio is short.

[Kakes]

So is it necessary to set the cooling rate at 9999 rather than letting the kiln cool naturally at that point (basically having no more segments) because of the holds at segment 5 & 7?

I just unloaded a cone 6 slow firing (I have a skutt). I included some green test tiles with washes and various commercial glazes brushed on, & they all came out pretty identical to a 06/6 two step firing. The ones that pinholed with the 2 fires also pinholed with the single fire, the ones I deemed successful with the 2 fires were also successful. I'm using mostly matte glazes though - maybe they're more forgiving? I'm using standard clays 420 & 710 which are both high grog. I was surprised how easy the green test tiles were to handle & brush glaze on. Now if I can only manage to not break the larger pieces...

i plan to try dhPotter's schedule in a week or two when I'll have pieces I can afford to experiment with & I'll report back then. Thank you again for everyone's input! This forum is the best thing that's happened to me since buying my kiln!

[dhPotter]

I don't know how else to tell the kiln to naturally cool while in the middle of a firing schedule. This is how to program a Bartlett V6-CF controller. Your controller may have a different command it uses to free fall cool. 

[Kakes]

dhPotter & others, is there any reason that this single firing schedule might put too much stress on larger flat pieces? My pieces are essentially like a cross between a tile & a platter. I've been putting sand and/or coils underneath when bisque firing to cone 6 with good results.

i guess I'm wondering whether a two step firing is "gentler" on large fragile items than a single firing?

[glazenerd]

Quartz inversion occurs at 563C, 1064F.  Do a search for the "quartz inversion" thread. Not that big of a deal for small pieces, but large, heavy, or large foot print pieces can crack. Program a 100F ramp from 1000 to 1100F if firing big pieces; then return to your normal firing cycle. 

T

[Kakes]

Thanks, glazenerd. I fear this is a stupid question, but if I program a 100F ramp from 1000 to 1100F, this means it will take an hour to go from 1000 to 1100F, right?  So, if I were to do dhPotter's schedule, which is 400/hr to 2050, I would slow it down to 100/hr between 1000 and 1100F, then resume 400/hr?

[glazenerd]

Correct.  When firing a large piece like you propose. You already mentioned putting sand under it, also a good choice. Kiln shelves have low thermal expansion, while your piece has significantly more at quartz inversion.

T

[Kakes]

Ok, thank you glazenerd. I did a search on quartz inversion as you suggested and fell deep down that rabbit hole -- it's a miracle that anything I made ever survived! I have a lot of questions but I think I should start another thread on the topic...

[dhPotter]

My firing schedule does not look "quartz inversion friendly".

I have always wondered why no clay problems with the firing schedule, going up, blowing past the 1063*F temp?? I can understand when coming down in temp because the kiln is cooling slowly all by itself. None of the broken pots show any clay problems. An evenly thrown bowl has a nice ring to it when rapped with a piece of wooden broom handle.

Is the 1063*F on the way up something to be concerned about or just keep on keeping on?

Thanks

[Stephen]

On 10/1/2018 at 10:28 AM, dhPotter said:

Stephen I may not have answered your question, but maybe I have. I did not find it difficult to use greenware. The worse happening was I broke the cup off a goblet stem, but it was poorly attached and used spooze to fix it. Then when I was pouring the liner I completely forgot this piece was the previously broken piece after the pour was finished. 

Steven Hill say single firing keeps him engaged with his work because he doesn't have the down time involved with a bisque firing. I do it to cut out a process that, to me, is not really needed and my time in the studio is short.

Ya did, thanks! I can respect that.

I think I am just to clumsy for it to work for me but seems cool to only flow through one firing. Moving around 50-60 pieces of greenware from drying rack through glazing and loading, I know I would have lots of 'accidents'.

Now we do have 2 kilns and that time sink of waiting for one to fire and cool before the next could be started caused a backup and was the reason for the 2nd one.  

[glazenerd]

DH:

inversion is on the way up. Unless you are firing large format platters or bowls with large foot rings, or heavy pieces: not something that will have a bearing on a firing. Porcelain is more susceptible than stoneware because of composition. 

T

[oldlady]

kakes, congratulations on the huge step of having your own kiln.  you will be learning a great deal over the next 20 firings.

i have been single firing for a number of years.  there are a few things you might think about.  you have not mentioned the brand name of the kiln you have or its size.  i use an L&L with a controller.   it is large enough for me to make huge, shelf size,  platters and trays.  sometimes i have a hard time fitting a rectangular tray into the  corners of the decagon because of its size.

my controller has a slow glaze setting.   i always use it, never tried outguessing the engineers or experts at the kiln factory on ramping up and down.  i use the slow glaze and choose the preheat which takes my dry clay to something over 200 degrees over a couple of hours, i think.   i have had no problems except when i do something stupid.   last month i refired a large platter because there was a dragonfly on it that i had not colored and some of the background was a little pale.  i reglazed it and then did the stupid thing.   i put it on the new shelf i had kiln washed but not put sand on.   naturally, the platter split down the center like a jagged lightning bolt.  when i opened the kiln, it had a 1/4 inch space between the halves.  it now lives on the wall of shame in  my studio.

my kiln controller offers me the choice of slow or fast firing or using my own ramp.   the ONLY way to use preheat, which i consider paramount, is to use the factory settings, not my own ramp.  so, i use preheat and slow glaze.   i pack my kiln very tight, sometimes using 9 shelves only 1 1/2 inches apart.   this makes a firing take a long time, about 12 hours these days with the elements no longer new.    and i always check for the temp when i close the peepholes and make sure all the water vapor is gone.  have a neat 8x10 mirror to do this with.   

for people who use a shared studio, you have no hope of trying single firing.   the shared firings make the tech set rules so everyone has a chance to get work successfully fired.  hence, bisque  firing is required.   once you have your own studio kiln, you can try single firing if you like and the work you do will allow it.   handling greenware is NOT difficult.  you have an instinctive soft touch, like picking up a baby,  that will save your work from  damage.  watching carefully as you move work, so you do not let it smash into something else that might be in the way, comes with your messing up a few times.  you quickly learn to let the clay DRY before firing.

i hope your new kiln gives you the results you want, kakes, and you love every piece you take out of it.  and hope you find that single firing, which has been done for centuries, will work for you.

 

 

[Kakes]

On 10/12/2018 at 12:44 AM, oldlady said:

kakes, congratulations on the huge step of having your own kiln.  you will be learning a great deal over the next 20 firings.

i have been single firing for a number of years.  there are a few things you might think about.  you have not mentioned the brand name of the kiln you have or its size.  i use an L&L with a controller.   it is large enough for me to make huge, shelf size,  platters and trays.  sometimes i have a hard time fitting a rectangular tray into the  corners of the decagon because of its size.

my controller has a slow glaze setting.   i always use it, never tried outguessing the engineers or experts at the kiln factory on ramping up and down.  i use the slow glaze and choose the preheat which takes my dry clay to something over 200 degrees over a couple of hours, i think.   i have had no problems except when i do something stupid.   last month i refired a large platter because there was a dragonfly on it that i had not colored and some of the background was a little pale.  i reglazed it and then did the stupid thing.   i put it on the new shelf i had kiln washed but not put sand on.   naturally, the platter split down the center like a jagged lightning bolt.  when i opened the kiln, it had a 1/4 inch space between the halves.  it now lives on the wall of shame in  my studio.

my kiln controller offers me the choice of slow or fast firing or using my own ramp.   the ONLY way to use preheat, which i consider paramount, is to use the factory settings, not my own ramp.  so, i use preheat and slow glaze.   i pack my kiln very tight, sometimes using 9 shelves only 1 1/2 inches apart.   this makes a firing take a long time, about 12 hours these days with the elements no longer new.    and i always check for the temp when i close the peepholes and make sure all the water vapor is gone.  have a neat 8x10 mirror to do this with.   

for people who use a shared studio, you have no hope of trying single firing.   the shared firings make the tech set rules so everyone has a chance to get work successfully fired.  hence, bisque  firing is required.   once you have your own studio kiln, you can try single firing if you like and the work you do will allow it.   handling greenware is NOT difficult.  you have an instinctive soft touch, like picking up a baby,  that will save your work from  damage.  watching carefully as you move work, so you do not let it smash into something else that might be in the way, comes with your messing up a few times.  you quickly learn to let the clay DRY before firing.

i hope your new kiln gives you the results you want, kakes, and you love every piece you take out of it.  and hope you find that single firing, which has been done for centuries, will work for you.

 

 

Thank you so much for all this information and your supportive words! (and apologies for my delayed response). I am finally doing my first single firing tonight and will try the slow glaze setting (to cone 6) this time. Next time I'll try dhPotter's schedule to compare.