jasmin Posted March 29, 2016 Report Share Posted March 29, 2016 I am new to using my own kiln, I have an electric one. I use cone 10 porcelain but I don't glaze, I just underglaze. The porcelain after being fired to cone 10 does not come out very white and this is southern ice so it should. The only thing i can think of is that I am putting on a bisque setting till cone 10 (which was recommended by the company L&L Kilns) since I don't do any glazing. Can someone help me out here? Please? Thanks in advance! Link to comment Share on other sites More sharing options...
neilestrick Posted March 29, 2016 Report Share Posted March 29, 2016 You're firing on a fast bisque setting to cone 10? What's your total firing time? Any reason you're firing to cone 10? You can get the same results at cone 6, and put a lot less wear and tear on your kiln. I doubt the firing cycle is contributing to the color issue. Some good photos would help us to see what you're talking about. Is it coming out gray or yellowish? Link to comment Share on other sites More sharing options...
Chris Campbell Posted March 29, 2016 Report Share Posted March 29, 2016 Southern ice is very white even raw, so are you sure it has not been contaminated somehow? Also, are you sure you are reading the L & L book right? I have never heard of bisque firing to Cone 10 ... Seems like it would take forever. ( I admit I could be wrong though!) I fire my Southern Ice to Cone 8 with a 20 minute hold ... This gives me an even Cone 9 throughout my kiln. I have not found much difference between firing to 10 or 9 myself. Link to comment Share on other sites More sharing options...
rayaldridge Posted March 29, 2016 Report Share Posted March 29, 2016 Chris, the L&L controller allows you to fire to any temp up to 10, using any of the 4 standard firing schedules There are slow and fast bisque and slow and fast glaze schedules. You're right that it would take much longer to fire a bisque program to 10. L&L recommends an initial break-in firing to Cone 5, if I recall correctly, using the bisque program. Link to comment Share on other sites More sharing options...
neilestrick Posted March 29, 2016 Report Share Posted March 29, 2016 They probably recommended the bisque schedule because (I'm assuming) you're single firing to cone 10. That way you don't have any issues at the low end of the firing. However porcelain dries very quickly and is very low in impurities, so using a faster schedule won't cause any problems as long as your work can handle it, that is if it's relatively thin and even. I often use the 'Fast Glaze' setting for bisque if I'm in a hurry, and have never had any problems. Link to comment Share on other sites More sharing options...
jasmin Posted March 29, 2016 Author Report Share Posted March 29, 2016 Hi thank you all for the replies. Yes Neil, I am single firing to cone 10. But the porcelain looks whitish gray at the end of the firing not the nice white that southern ice yields. And my work isn't super thin. it is southern ice and it says it should be fired to cone 9 or 10, that is why I went so high but I wouldn't mind if I could fire it to a lesser temp.. The L&L costumer service guy told me to bisque it but he didn't sound too sure himself. But I think his advice is wrong. Because even though there was no loss, the color is way off. Do any of you have a suggestion on how I should fire next time. The slow bisque preset on the kiln takes 12 hours and I am putting in my greenware bone dry... It hasn't been contaminated, this has happened with another batch of southern ice. It looks grayish in real life than the pic attached. My camera just sucks lol. Link to comment Share on other sites More sharing options...
glazenerd Posted March 30, 2016 Report Share Posted March 30, 2016 Will go with Neil on this: highly unlikely the firing cycle is producing greyish color. All clays have iron or magnesium in them: some even have trace amounts of manganese. As general rule, the darker the clay the more iron, the lighter the clay -much less. White porcelains (Frost) or Aardvark still have some iron in them regardless of their color. The whiter raw clays usually have much higher calcium contents than darker clays ( in general). From reading your post, you said this has happened before. So can I assume that it happened with some boxes, then stopped when you got new boxes, then started again with this batch? Clays like all minerals have veins of purity/contaminants: iron and magnesium would be very high up on the list of culprits. White porcelain bodies usually run 0.10 to 0.18% iron.: takes very little to change the color. Nerd Link to comment Share on other sites More sharing options...
oldlady Posted March 30, 2016 Report Share Posted March 30, 2016 can you contact the clay manufacturer to get a clarification on using their product the way they recommend? the kiln will do whatever that is once you know what it should be. Link to comment Share on other sites More sharing options...
jasmin Posted March 30, 2016 Author Report Share Posted March 30, 2016 Thanks I will do that too. Link to comment Share on other sites More sharing options...
neilestrick Posted March 30, 2016 Report Share Posted March 30, 2016 Most of the samples of cone 10 clay bodies that the manufacturers show are fired in reduction, and just like stoneware bodies, reduced porcelain (gas fired) looks different than oxidized (electric fired). However usually impurities are more evident in reduction than oxidation so it's a bit odd. Link to comment Share on other sites More sharing options...
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