Jump to content

Cone 5 Glazes - Matured Or Not..?


Rex Johnson

Recommended Posts

I fired my new to me Olympic 2827G propane kiln for the first time Sunday.

More on that here: help needed evening out my kiln temp differences

I haven't used glazes for some time though used the Laguna Versa cone 5 glazes in aother kiln with decent results.

 

I used mostly Moroccan sand MS128 Iron Phoenix and MS97 Mandarin Orange plus some Versa glazes this time.

I could use some feedback.

 

First pic is a bottom shelf piece, smooth and matured.

Second pic is the same next to a a mid-top shelf piece same glaze, but is rough and dry.

Third pic is the MS97 which also isn't glossy and mid shelf.

The mid and upper Versa glazes weren't glossy either.

 

All glazes where sprayed evenly.

The kiln of course fired hotter on the bottom where those pieces seemed matured.

The bottom cones fell nearly an hour before the top cones.

Total firing was 6+ hours including a 45 minute soak.

I was afraid I'd over fired as the Pyrometer read 2250F at one time.

 

At this point, even though the kiln was up to and past cone 5, I'm thinking maybe I should shoot for cone 6 and a longer soak?

Or maybe just a longer firing and soak both. This unit can fire very quickly as many know.

I'm all ears here. Kind of scratching my head on this one...

 

 

IMG_4463-L.jpg

IMG_4464-L.jpg

IMG_4468-L.jpg

 

Link to comment
Share on other sites

Your first photo does not look over fired. But it is hard to tell from pics. I have used many of the Laguna Morroccan Sand glazes. I have found that most will be over fired at cone 6, but not all. Do a search, there are many threads here on how to even out your firing. 6 hours is really fast for a glaze firing. Was your kiln full? I found mine fires more even when totally full. Lightly loaded areas have a tendency to over fire and cool to quickly.

Link to comment
Share on other sites

Chantay, Thanks for your input, I don’t seem to be getting any on this thread…

I have read all I can find on the MS glazes and this kiln in particular including yours.

Good stuff.

 

The firing was full albeit mostly with bowls and s few junker pots. I don’t make a lot of smaller pieces to fill the spaces.

The main reason I bought this monster is t fire 10â€-12†bowls.

 

I’m thinking the same as you, the firing time is short. This beast will fire to temperature very quickly due to its design or lack thereof.

So, this is what I'm going to do. I’m going to lengthen the firing/soak by at least 2 hours.

There is also the issue of flame exposure, making the glazes have hot spots.

(See next post)

Here’s  few pics of the stack:

 

Bottom shelf 6" off the floor.

IMG_4441-L.jpg

 

Second shelf had the shallow bowls, and third was 1/2 shelf.

That's the flue blocker in the middle.

IMG_4443-L.jpg

 

chimney

IMG_4460-L.jpg

Link to comment
Share on other sites

Now, Since this cylinder just shoots the flames straight up the sides and out the flue I did what another suggested and made 2 ports to direct flame under the bottom shelf.

These two pics are of the first port modification:

IMG_4438-L.jpg

 

IMG_4434-L.jpg

 

This time around I'm redesigning the targets so that all 4 burners will hopefully swirl under the bottom shelf.

I want flame away from the ware.

I'll still have a hotter on the bottom issue. I don't think that's fixable unless I make it into a downdraft kiln.

This and slowing and lengthening the firing just might help.

Sorry for all the talk-a-lot folks, but I like to write my thoughts down ;) ...

 

This is the new design...

IMG_4469-L.jpg

 

IMG_4470-L.jpg

Link to comment
Share on other sites

I think it’s going to be hard to get a definitive answer on how fast you can fire those commercial glazes as you have no way of knowing what their make up is. In industry very rapid glaze fires can be done because they use highly fritted glazes with very low loss on ignition with very even kiln temps throughout the kiln. 


 


With your kiln firing so unevenly I would definitely slow down the firing and try and put more mass in the hotter bottom part of the kiln and less mass in the cooler part. I’m useless as gas kiln design so hopefully others will chime in on how to even out the temp better.


Link to comment
Share on other sites

Noted.

I have fired quite a few of the Versa glazes with total maturity in aother kiln though.

 

With all my goings on here, the main mystery is why the glazes appear to be not matured even though all the cones had dropped.

 

The few mature pieces where at the bottom and reached temp first, so therefore had a longer at-temperature firing.

Theorizing here, but I think a longer overall firing at temp (soak) should help.

I'm going to re-fire some of these pieces in the next test.

Link to comment
Share on other sites

With all my goings on here, the main mystery is why the glazes appear to be not matured even though all the cones had dropped.

 

I was going to post this earlier, but since I don't know a lot about gas kilns I didn't post it. Since you asked this specific question I am going to answer it to the best of my ability.

 

If your cones are bent, then your heat work was achieved. This however doesn't mean the proper heatwork was required for your glazes to preform correctly was met. Glazes have to do three things: begin to melt, form their surface, and cool/heal properly. If your firing quickly and cooling quickly you can skip the middle step. Which is why if you fire to quickly to cone 6, you can end up with vastly different surfaces on the insides of bowls or cups with the same glaze on the outside doing just fine. This is also the reason you can have pots on one shelf do fine and pots on another shelf look terrible with the same glaze and the same heatwork. 

 

For example, I used to fire cone 6 in my electric kiln in 6 hours and 45 minutes. I would get good results on the outsides of my pots and bad results on the inside. I was achieving the heat needed on the outsides of my pots, but not enough on the inside. Which caused me to have really odd surfaces on the most important parts of my pots.

 

I later learned that I needed to do a soak to even the kiln, well that soak raised my cone to high. So I came up with another solution, fire slower to the maturity and use a hold to achieve heatwork required.

 

I started going to 1700 then at 108F/h to 2150 then holding for 15-20 minutes depending on how dense the load was. This worked pretty well and the insides of my pots started looking like the outsides. Later as I begin to vary the amount of pots in my kiln by a great deal I realized I was having bad surfaces again as the kiln was cooling to quickly and my pots weren't healing over properly as they cooled. I had surface defects I didn't want. So I added another step, I would control my cooling down to 2050 and hold my kiln for another 30 minutes. Then again at 1950 for another 30 minutes. This allowed my glazes to cool and heal over to form beautiful surfaces. 

 

After this I started thinking about how the next part is important too, and I didn't want larger denser loads that cooled slower from 1900 to 1500 to look different from my smaller loads. So I created a controlled cooling of 200 an hour to 1500. So now no matter how dense or sparse the load is. I always get constant results, or as close as I can control it.

 

So think about all that when you think about your kiln. If the top part of your kiln is much cooler, your either going to need to put glazes that have a lower melting point and heal over faster, or your going to need to figure out a way to even out your kiln as it approaches the heat work needed for cone 6.

 

My main concern is I have no idea how reduction kilns work, and all of the above could be completely incorrect for what your doing. But I assume glazes in reduction have the same types of heat melt point requirements and surface problems that oxidation glazes have. You might achieve those surfaces in a different way, but every single glaze has different melting, running, healing properties that need to be met. To me the red glaze in your last picture looks to be incorrectly melted. It looks like it started and then stopped, I can't tell by the pictures but it looks to have a lot of surface defects that probably would have healed if more heatwork was added and it was decreased in temp slower.

 

Another thing to think about is that normally gas kilns are in very thick brick and they cool very slow. I am assuming your kiln cools pretty fast as it looks to just be similar to an electric kiln in brick size and type. Which means you might have to figure out some way to control your cooldown slightly so that everything melts and smooths properly.

 

I just want to note that I have never fired reduction, so I could be incorrect in a lot of my assumptions, but I have read a lot about glaze problems as I have worked on my surfaces for the last 4-5 months endlessly.

 

Hope this helps a little. Good luck on your next test!

Link to comment
Share on other sites

Bingo! Thanks for the input Joseph.

That is exactly what I'm thinking as well.

 

A calculated ramp up at a slower pace, then a longer soak at cone 6, and finally ramp down slower.

This is great.

I'm getting hopeful ;)

 

There will be a collection of glazes, some used in the past and sitting on the shelf and a couple I used last firing plus I'll re-fire a few from the last firing.;

 

Coyote Shino ^6                 sunriseshinosmall.jpg    I think this is the one I have...

 

Coyote Pam's Blue ^6        pams_blue_small.jpg    I've used this before

RE-FIRE MS128 Iron Phoenix ^5 - ^6      ms128.jpg smoothed out nicely when fired at the bottom, but it was gold/beige in color

RE-FIRE MS97 Mandarin Orange ^5 - ^6 ms97.jpg underfired w/rough surface

RE-FIRE MS310 Roman Violet ^5 - ^6     ms310.jpg   also underfired and looked like a very pale pink w/rough surface

 

I know there's alot of variation in the glazes here but I think the firing itself is the key.

More after the weekend...stay tuned...

Link to comment
Share on other sites

Second firing went pretty good. Cones melted down bottom and mid shelves and ^6 on top bent.

I reduced for 30 minutes at about 1650 degrees for 30 minutes on the way up.

Also soaked 30 minutes at the top and generaly slowed the schedule down to 8+ hours.

 

I used the Coyote glazes I had, ^6 Shino and Pam's blue and also a ^6 clear blue/green I had laying around.

Everything matured and no drips.

 

I did have a couple pots that showed spiral cracks thru the body that otherwise wouldn't have shown.

Maybe due to it being ^5 clay?

Maybe I should start using cone 10 clay.

Will the ^5-6 glazes react the same on ^10 clay?...I use Laguna B-Nix ^5 clay.

 

Laguna MS128  ^5-6 Iron Phoenix - actually kind of had some crystals. (on the top shelf)

Turned out in a blue/gray mottled with gold-ish refrain. Last firing it looked smooth and solid gold/tan.

The interior is a Laguna ^5 MS-311 Black which appears fine.

I like this.

 

IMG_4502-L.jpg

 

Coyote Shino ^6 - totally matured and colors as they should be. (on the bottom)

 

IMG_4509-L.jpg

 

The clear blue/green ^6 (on the bottom) nicely matured and shiny.

This has cobalt applied on the rim prior to bisque.

 

IMG_4513-L.jpg

 

So far so good.

 






 





 

Link to comment
Share on other sites

Looks good.

 

For your clay body, try to find something that is like ^6-7 or ^6-8. If your using a ^5 body and your bottom shelf is hitting ^7-7.5 might be causing the issue you describe.

 

If you go as high as ^10 and your firing to cone ^6 your going to have glaze fit issues as well as your clay not being vitrified which will make your functional pots weaker.

 

Or you could put different clays in the bottom part and cooler clays in the top part. So load cone ^6 clays in top, and ^6-8 clays in bottom. 

 

Just some ideas. Your glazes look much better than the previous firing, everything looks like it had time to melt and heal much better. Nice job.

Link to comment
Share on other sites

Thanks G,

I'm sort of limited to Laguna Clays as they are close buy, I can pick it up.

 

The other ^5 Versa glazes didn't improve, the orange and the violet, and gold. However those were just put back in and re-fired.

I figured they might come glossy at the higher temp, but no, not really.

No biggie, to many variables there.

I can always fire those Versa glazes separate firing.

 

O.T.

Had some pretty surprising results firing them in my other big clunky gas kiln.

Fun with maiolica...

 

IMG_3540-L.jpg

Link to comment
Share on other sites

  • 3 weeks later...

Well, happy to say I had a near 95% good glaze test firing using The Pete's Black, Malcolm's Shino, and the Ceramics Daily Temmoku found here.

3 pieces plus a load of tiles. Everything very inspiring.

again the bottom of the Olympic 2827G fired hot, probably ^7, where the top was ^5-6, but reduced well.

The bottom piece got hot enough to fracture the foot, but I have a plan for that next go-round

These where all glazed with a cup and bucket, therefore thick and thin.

 

Malcolm's Shino ^6-10 (bottom) w/RIO and some other splatterings, orangey to white-ish.

Really pleased with this.

 

IMG_4690-XL.jpg

 

Pete's Black, ^5-10 (middle) actually lustered a bit. Photo doesn't catch the luster.

 

IMG_4691-XL.jpg

 

Temmoku ^ 6-10 (top) a nice rich reddish, with almost orange where it broke or was thinner.

 

IMG_4689-XL.jpg

Link to comment
Share on other sites

6 hours is a very fast fire. I'm not a cone 5-6 person but fire hotter and there is time needed so have the glaze mature-That time is usually achived by two ways first a slow glaze melt at your high limits or if its a fast fire then hotter temps by a cone or two depending on firing speed.

There is a time temp relationship to the maturing of glazes. It's not a single function.

Fire slower or hotter-take your choice-both will work.

I choose the slower approach.

Mark

Link to comment
Share on other sites

Yeah, these last two firings where definitely long and, er, slower, and hotter than the first.

Both with better results than the first.

 

I candled for a good 1/2-2 hours until it reached 500-600 degrees then brought it up to reduction temp at a gradual ramp.

I reduced for at least 30 minutes in the 1640-1730 range and after that it was another two hours up around 2100.

After that as slow as possibly to cone 6, really tapering off the gas and monitoring the flue. This kiln is super touchy to fine adjustments.

Trying to catch up the top cones to the bottom cones is a slow dance.

Once to temp I soaked for at least an hour and shut it down with full pluggage, including covers on the burner ports.

 

Total time was about 9 hours this go-round.

 

At any rate, I think Ive got her sorted considering the design.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.