swalger Posted May 7, 2017 Report Share Posted May 7, 2017 Our studio inventory consists of Cone 6 Clay Bodies and Glazes. We use L&L Electric Kilns primarily. Our local suppliers have not kept a reliable stock of Cone 6 inventory and we have started looking into other options. One is Aardvark. They do not seem to supply much Cone 6 Clay and I was wondering to what extent Cone 5 clay will handle Cone 6 firing. To be clear, we would be looking to fire Aardvark, Cone 5 Clay bodies with Cone 6 glazes in our electric kilns until we can either find a reliable source of Cone 6 Clay or migrate our inventory over to Cone 5 Clay and Glazes. Might anyone have working experience in this situation? Link to comment Share on other sites More sharing options...
Guest JBaymore Posted May 7, 2017 Report Share Posted May 7, 2017 Most of their clay bodies show a rather high Apparent Porosity rate (2% and up) ........ which says they likely will tolerate cone 6 just fine. SOme are so high as to be questionable for functional table wares at cone 5. But as always........ test, test, test. best, .....................john Link to comment Share on other sites More sharing options...
Pres Posted May 7, 2017 Report Share Posted May 7, 2017 As John says, test. . . often. I have used cone 5-6 bodies quite a while, and as I have an L&L that is fired by site cones with no setter, I have overfired when tired, or have over napped. I can say that I have fired to cone 8 and had bloating, fired to cone 7 and no problem, but don't recommend it. I do have a tendency to fire to a hard cone 6, where cone 6 is touching the shelf, and 7 is nearly 40 degrees. I have found that for my colors, thickness of glaze, and clay bodies that this is my best target. I use Standard Ceramics and over the years have used 112,211, 225, 553, and now 630. All have been great to work with, as have been the folks at SC in PIttsburgh. I don't notice a location for you on your profile, that may help folks when you ask questions like your present one. best, Pres Link to comment Share on other sites More sharing options...
Denice Posted May 7, 2017 Report Share Posted May 7, 2017 The only problem I can think of is that the top of the kiln could get to C7 and the work might slump. I had that happen when I was holding a temp and down firing, Other than that I think you would be alright and you pots will be truly vitrified. Denice Link to comment Share on other sites More sharing options...
glazenerd Posted May 7, 2017 Report Share Posted May 7, 2017 (Long three paragraphs of detailed chemical explanations, with two more paragraphs of formulation differences) yes, it will work just fine. Nerd Link to comment Share on other sites More sharing options...
Pres Posted May 7, 2017 Report Share Posted May 7, 2017 I often down fire, but not as much since I got the thicker lid. I like to hold a bit around ^6.5, then drop 30% for 1/2 hr. Kiln pretty even as I do not turn top all the way up, and witness will be very slightly more than target at mid peep. best, Pres Link to comment Share on other sites More sharing options...
BornonSunsetCeramics Posted November 11, 2017 Report Share Posted November 11, 2017 I'm having issues with an Aardvark cone 5 clay body right now! Particularly, SBF, a clay body I love to throw but when fired to cone 6... bloat!! I even used Steve's custom bisque firing problem to try to rid the issue (iron - gases) and alas, my glaze fire to cone 6 with a 10 minute soak came out bloated. At cone 5 it fired fine, and they assured me that with little difference between 5 and 6 it would be ok, and I trust them, so I'm over here scratching my head. At 5 I wasn't in love with my glaze maturation so I'm curious how long I can soak at 5 before bloating occurs... Link to comment Share on other sites More sharing options...
neilestrick Posted November 11, 2017 Report Share Posted November 11, 2017 11 hours ago, BornonSunsetCeramics said: I'm having issues with an Aardvark cone 5 clay body right now! Particularly, SBF, a clay body I love to throw but when fired to cone 6... bloat!! I even used Steve's custom bisque firing problem to try to rid the issue (iron - gases) and alas, my glaze fire to cone 6 with a 10 minute soak came out bloated. At cone 5 it fired fine, and they assured me that with little difference between 5 and 6 it would be ok, and I trust them, so I'm over here scratching my head. At 5 I wasn't in love with my glaze maturation so I'm curious how long I can soak at 5 before bloating occurs... I would first try getting rid of the soak at cone 6. You're just adding heat work there, getting to 6+. Link to comment Share on other sites More sharing options...
BornonSunsetCeramics Posted November 11, 2017 Report Share Posted November 11, 2017 Hi Neil! I've tried just going to 6 with this clay and it bloated as well. The last firing was a batch that I ran custom bisque firing on before the glaze fire (as opposed to just running the Skutt "slow" program that comes on the kiln. I've fired it to cone 5 with no issue, I just wasn't thrilled with my glaze. Can you recommend a soak time at cone 5? Thanks! Link to comment Share on other sites More sharing options...
neilestrick Posted November 11, 2017 Report Share Posted November 11, 2017 If it bloats at 6, I would get a different clay. Many glazes need to go up to 6 to work well, so it will be limiting to be stuck at 5. But if you really want to make it work, I would start with a 10 minute hold and increase by 10 minute increments each firing. It'll take a few firings to figure it out. Put some cones in every time to see where you're actually getting. It could be that it works at 5 3/4, but bloats at 6. Link to comment Share on other sites More sharing options...
Guest JBaymore Posted November 11, 2017 Report Share Posted November 11, 2017 19 hours ago, BornonSunsetCeramics said: I'm having issues with an Aardvark cone 5 clay body right now! Particularly, SBF, a clay body I love to throw but when fired to cone 6... bloat!! I even used Steve's custom bisque firing problem to try to rid the issue (iron - gases) and alas, my glaze fire to cone 6 with a 10 minute soak came out bloated. At cone 5 it fired fine, and they assured me that with little difference between 5 and 6 it would be ok, and I trust them, so I'm over here scratching my head. At 5 I wasn't in love with my glaze maturation so I'm curious how long I can soak at 5 before bloating occurs... Just as an added thought..... are you using witness cones on the shelves, or trusting the computer program to say you are going to cone 6 with a soak? If you are trusting the computer........ you may be going with more heatwork than a cone 6 level... and that might be the source of the bloating. best, ................john Link to comment Share on other sites More sharing options...
Min Posted November 11, 2017 Report Share Posted November 11, 2017 3 minutes ago, JBaymore said: Just as an added thought..... are you using witness cones on the shelves, or trusting the computer program to say you are going to cone 6 with a soak? If you are trusting the computer........ you may be going with more heatwork than a cone 6 level... and that might be the source of the bloating. best, ................john ha ha, I think I was typing at the same time you were, on the other thread about this clay. Link to comment Share on other sites More sharing options...
C dub Posted April 1, 2019 Report Share Posted April 1, 2019 I am using a new clay and am not super experienced in pottery and ceramics. I taught it at a very basic high school level and had a lot of help with presetting the kiln for the work that needed to be done with a person who had studied ceramics. Now I am at a new school and the kiln is the same brand but has very different control panel. The other art teacher here seemed to know how to use it and showed me what he used to do, he is also very unexperienced. I was told the clay we had was a cone 6 and fired it accordingly. I did some testing of this clay at a local place and when they cam out of their kids they were the nice light pink color you would expect. This round of student work came out a light gray and doesn't seem to be right. I'm wondering if we didn't hold it long enough or it isn't firing properly somehow? Anyone have any suggestions or ideas and what we did wrong- besides not running a test before loading a whole class of projects in (my colleague assured me that he knew what he was doing...)? Link to comment Share on other sites More sharing options...
Hulk Posted April 1, 2019 Report Share Posted April 1, 2019 Hi C! Some questions - electric kiln? Can you identify the clay(s)? The controller type/model? Given your clay (and glazes!) should mature at cone 5/6, your bisque (first firing) target temp should be well below that (I'm shooting for 06); for the glaze fire, you'll go hotter... From there, my (very limited!*) experience says let cones be your guide - put a cone pack (your target, one higher, one lower) where you can see it (use appropriate glasses !!!); better yet, put a cone pack on each shelf, and even better, be able to see all of them whilst firing. Cones tell you what is happening (what happened) from the clay's point of view - heat plus time. Your thermocouple won't reflect "heat work" and typically they read high or low... Perhaps you're not glazing? Same deal, cones are the way to go. *very limited, yah, have run two bisque and glaze loads in my very used manual kiln, have learned loads (e.g. made many mistakes); details to follow under my status, having just unloaded glaze firing yesterday - just have t'finish assessing, then snap some pics... Link to comment Share on other sites More sharing options...
Min Posted April 2, 2019 Report Share Posted April 2, 2019 10 hours ago, C dub said: I was told the clay we had was a cone 6 and fired it accordingly. I did some testing of this clay at a local place and when they cam out of their kids they were the nice light pink color you would expect. This round of student work came out a light gray and doesn't seem to be right. I'm wondering if we didn't hold it long enough or it isn't firing properly somehow? Sounds like you did a firing of greenware up to cone 6, is this correct? Off-white clay bisque ware is sometimes a slight peach/pink colour and will mature to an off-white / buff / greyish white when fired to maturity. Are the pieces glazed? Link to comment Share on other sites More sharing options...
C dub Posted April 2, 2019 Report Share Posted April 2, 2019 yes, that is what I did. Was I totally wrong in doing that? Those were the directions given to me by the clay vendor... Link to comment Share on other sites More sharing options...
Pres Posted April 2, 2019 Report Share Posted April 2, 2019 C dub, you may find that your supplier told you ^06, not ^6 for your bisquefire. Identify your clay body for us, and we can help you out a bit more. best, Pres Link to comment Share on other sites More sharing options...
C dub Posted April 2, 2019 Report Share Posted April 2, 2019 19 minutes ago, Pres said: C dub, you may find that your supplier told you ^06, not ^6 for your bisquefire. Identify your clay body for us, and we can help you out a bit more. best, Pres Pres, it is something called B mix. Does that help? Link to comment Share on other sites More sharing options...
Pres Posted April 2, 2019 Report Share Posted April 2, 2019 Is there a number for the clay body, like WC-401? There are a lot of B-mix clays by Laguna out there, so a number would be helpful. These are porcelainous bodies, and quite popular. best, Pres Link to comment Share on other sites More sharing options...
Min Posted April 2, 2019 Report Share Posted April 2, 2019 "yes, that is what I did. Was I totally wrong in doing that? Those were the directions given to me by the clay vendor..." It should have been a firing to a lower cone for the first firing. Cone numbers go down with the firing temperature, cone 14....6,5,4,3,2, 1 it then goes to 01, 02, 03.... etc down to 022. Most people glaze bisque ware, this is when the clay is fired to a cooler cone than the glaze firing, bisque cone can range but usually in the 06 - 04 range. After the first firing if you touch your tongue to the clay it should stick a little bit. If it doesn't stick then it will no longer be porous enough to get a glaze on it easily. You have a load of clay that has been fired to cone 6 and isn't going to be porous so getting the glaze to stick to it is going to be difficult. If your students are using brushing glazes you could try glaze the pieces but it's going to take at lot of patience and results probably won't be stellar. The confusion over firing cone number has happened to a few people here on the forum, going forward just remember that for bisque (first firing) you want to go to approx 06 to 04 and for a cone 5/6 clay like WC 401 BMix you want the glaze fire to go to cone 5 or 6. Also, the glazes you use must be rated to go to cone 5 or 6 also. (unless you want to run experiments) Any chance the students made just decorative work and they could use acrylics on it? Link to comment Share on other sites More sharing options...
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