sulamaye Posted September 15, 2012 Report Share Posted September 15, 2012 Hi, I've just moved from a hard water area to a soft water area and my first stoneware firing in a small mini bar controlled kiln using no. 8 like I usually do resulted in overfiring/ running of the glazes. I am assuming that the water is making the rhodes white I am using more fluffy, that's how it feels and I need to fire lower than my kiln has been achieving by going straight up full blast to min bar shut down. Am I right in thiniking that if I ramp the firing more slowly this will make the mini bar bend at a lower temperature? Or is it the other way round and the faster I fire the higher the bar bends? Thanks for your help Link to comment Share on other sites More sharing options...
neilestrick Posted September 15, 2012 Report Share Posted September 15, 2012 Yes, the slower you fire the lower the temperature of the cone. But it won't matter if you fire fast or slow, the cone will bend when it has enough heat work, and the melt will be the same. Heat work is a function of temperature over time. You can cook a roast at 350 for an hour or 275 for 3 hours, but either way you get a cooked roast. I would first check the calibration of your kiln sitter before altering your firings or glazes. Link to comment Share on other sites More sharing options...
sulamaye Posted September 16, 2012 Author Report Share Posted September 16, 2012 Yes, the slower you fire the lower the temperature of the cone. But it won't matter if you fire fast or slow, the cone will bend when it has enough heat work, and the melt will be the same. Heat work is a function of temperature over time. You can cook a roast at 350 for an hour or 275 for 3 hours, but either way you get a cooked roast. I would first check the calibration of your kiln sitter before altering your firings or glazes. Yes you're right it didn't work if anything they are more fired, £500 of work down the drain. I really don't think it is the kiln, I am checking temperature with an electric pyrometer as well and there's no reason to think there is anything wrong with the kiln - I am firing it regularly over the year and it is a lovely realiable little kiln. I'm pretty sure when I get my bigger kiln wired in the glaze will come out the same - whereas what I do know is that the water here is very soft and on the other side of the UK it was very hard. I can feel how different the glaze is, it is fluffy. Has anyone any experience of different waters and their effect on glaze? What I am going to try now is watering some glaze down to really thin and testing. Anyone any other ideas? Link to comment Share on other sites More sharing options...
DAY Posted September 16, 2012 Report Share Posted September 16, 2012 If you think the water is the problem, then "harden" it. Wiki sez: Water's hardness is determined by the concentration of multivalent cations in the water. Multivalent cations are cations (positively charged metal complexes) with a charge greater than 1+. Usually, the cations have the charge of 2+. Common cations found in hard water include Ca2+ and Mg2+. These ions enter a water supply by leaching from minerals within an aquifer. Common calcium-containing minerals are calcite and gypsum. A common magnesium mineral is dolomite (which also contains calcium). Rainwater and distilled water are soft, because they also contain few ions.[1] A bit of Googling should turn up more options. Link to comment Share on other sites More sharing options...
sulamaye Posted September 16, 2012 Author Report Share Posted September 16, 2012 If you think the water is the problem, then "harden" it. Wiki sez: Water's hardness is determined by the concentration of multivalent cations in the water. Multivalent cations are cations (positively charged metal complexes) with a charge greater than 1+. Usually, the cations have the charge of 2+. Common cations found in hard water include Ca2+ and Mg2+. These ions enter a water supply by leaching from minerals within an aquifer. Common calcium-containing minerals are calcite and gypsum. A common magnesium mineral is dolomite (which also contains calcium). Rainwater and distilled water are soft, because they also contain few ions.[1] A bit of Googling should turn up more options. Thanks - perhaps I should add more dolomite then, but seems slightly adhoc. I could also import water 300 miles. But I think I'll start by adjusting the the glaze from single cream to milk in thickness. I will report back in case anyone else has that problem. Link to comment Share on other sites More sharing options...
neilestrick Posted September 17, 2012 Report Share Posted September 17, 2012 If you typically fire in a different kiln than the one you are using now, I would definitely check the calibration of the sitter. The two kilns could be calibrated very differently. If all is well there, I would not alter your glazes, but rather fire a cone lower. It's the simplest solution. Plus the results from kilns of different size can be very different. My little test kiln gives radically different results than my larger kilns. Link to comment Share on other sites More sharing options...
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