Unglazed Posted August 30, 2016 Report Share Posted August 30, 2016 I just purchased five containers of Amaco Potters Choice cone 5-6 glazes. I just did a firing at cone 5 with the glazes and none of them vitrified. I also fired a few small pieces of bisque ware with the glazed items and I think that they turned out fine, although they appear more pink than what I have seen before. The glazed pieces look like they haven't been fired at all. I am trying to figure out what I did wrong, or what my kiln did wrong. I cannot imagine that 5 separate containers of Amaco glazes that were made at separate times would be at fault. Here are some details: - I cracked the kiln an inch from the beginning of the firing to the end. I did this because 2 of the small pieces I was bisquing were not bone dry yet and I thought that this could help air out any leftover moisture. The pieces were not completely moist. These were not the pieces I glazed. - The whole firing from it's peak to cooling was about 12-15 hours. - I have a Paragon xpress 1193 which I purchased in January of 2015. I have fired it to cone 5 before but never beyond that. I do not run my kiln frequently, I usually fire to cone 05 for low fire items. - As far as I know, the glazes were not shipped to the store frozen. -The items that were glazed were bisqued to cone 5. What do you think is the culprit? Do you think that my kiln needs to be repaired possibly? Suggestions? Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted August 30, 2016 Report Share Posted August 30, 2016 Sounds like you did 05 by mistake if the bisque look pinker than usual. If you did do a cone5 but also cone5 bisque the glaze application could be way too thin and not have enough glaze to melt. Link to comment Share on other sites More sharing options...
Rex Johnson Posted August 30, 2016 Report Share Posted August 30, 2016 ...could be, but if not, when in doubt with cone 5-6 glazes, fire to a complete cone 6. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted August 30, 2016 Report Share Posted August 30, 2016 I agree with the first diagnosis and the suggestion by Rex.. FIre again and use a cone 6. MArcia Link to comment Share on other sites More sharing options...
ayjay Posted August 30, 2016 Report Share Posted August 30, 2016 My first kiln was quite small and virtually gifted to me. It only fired to a maximum of 1200°C. I used to use Amaco PC glazes and always fired them to 1185°C with a 20 minute hold and they were fine. Istr reading on the Amaco website that many of their PC glazes are actually better at ^5 than at ^6. Link to comment Share on other sites More sharing options...
Pugaboo Posted August 30, 2016 Report Share Posted August 30, 2016 Ummm this might be a silly question but did you put a cone on a shelf in the kiln when you fired? If so, did it reach a full and proper bend? If it didn't then your kiln never reached cone 5 despite what the controller might have said. T Link to comment Share on other sites More sharing options...
neilestrick Posted August 30, 2016 Report Share Posted August 30, 2016 If you were bisque firing some pieces along with the glaze pieces, then you were firing to cone 05, not 5. You should not leave the lid cracked during the firing- you're just wasting electricity and you could cause the controller to get an inaccurate read. Crack it at the beginning if you want, but once it's above a few hundred degrees you're not gaining anything. In fact the top of the kiln will be colder than the rest. Leaving the top peep out will work just fine, or if you're running a vent then you shouldn't be leaving anything open because you're just spoiling the draft of the vent. Link to comment Share on other sites More sharing options...
Unglazed Posted August 31, 2016 Author Report Share Posted August 31, 2016 I am almost certain that I fired to a cone 5 because after I turned my kiln off and on again, the controller suggested that I fire at cone 5 (where it left off). I will fire again tonight at cone 6 and I will post the result here again. I will close the lid, take the bisqued ware out and just leave the stuff for glaze. I am suspicious of the last firing because cone 5 usually takes about 20-24 hours and this was not the case in this instance. I also used plenty of glaze, I do not think that was the problem. No I did not use a cone to watch the temperature, my kiln is small enough that I usually don't need to use cones. Link to comment Share on other sites More sharing options...
winstonzeddmore Posted August 31, 2016 Report Share Posted August 31, 2016 I know it can be a hassle to use witness cones with every firing, but when you're having a problem - or fire as infrequently as you do - the witness cones will tell you what did happen. Also I'm wondering why you fired bisque so high? It will leave the clay more tightly grained and can make glazing difficult... Link to comment Share on other sites More sharing options...
Unglazed Posted August 31, 2016 Author Report Share Posted August 31, 2016 I am self taught, that is why. I am 22 years old and bought my own kiln. I thought that my professor has bisqued to 10 for both bisque and glaze. I could be wrong. I have no idea honestly, I find this very frustrating. I feel like the only way I can know these things is to fail constantly, which is very time consuming. What temperature should I bisque it too? I am also confused because the bag of clay I have only says cone 5 on it. Does that mean that is its maximum temperate? It did not give me a range. Would firing to cone 6 for glaze ruin it or make it explode? Link to comment Share on other sites More sharing options...
Pugaboo Posted August 31, 2016 Report Share Posted August 31, 2016 It is very frustrating when you first start out. Don't give up, keep trying but give yourself the tools to make it easier for you to achieve good results. I would highly suggest getting a few books on firing pottery from the library I think they will be immensely helpful to you. Now to answer a question or 2... Bisque firing is usually done to cone 05 or 04. The reason is the clay needs to have the impurities burned out and the clay will become semi-vitrified yet still porous and is easier to handle for glazing. If you fire bisque to cone 5 the clay is completely vitrified. This will make the clay very hard and tight and unable to soak up enough glaze to do the job. Witness cones can be a hassle but are immensely helpful if you are having issues. I would suggest on your next firing to put one in so you can see how much actual heat work occurred during your firing. Knowing this will make it easer for you to figure out if you have a clay, glaze or kiln issue. If you don't have one download an Orton chart and use it to compare your cone results it will tell you the temperature your kiln achieved. Hopefully that will answer a lot of questions for you and give you a direction to go to get the results you want. Good luck and let us know how it goes. T Link to comment Share on other sites More sharing options...
No Longer Member Posted August 31, 2016 Report Share Posted August 31, 2016 I know it can be a hassle to use witness cones with every firing, but when you're having a problem - or fire as infrequently as you do - the witness cones will tell you what did happen. Amen, I fix a lot of stuff for various folks; a witness cone is a great tool to find out exactly whats going on. Size of the kiln has nothing to do with whether or not you should use cones or the ability of any given kiln to reach desired temp. If it ain't workin' right, it ain't workin' right. A cone will let you know if it did get to temp or not. I have no idea honestly, I find this very frustrating. I feel like the only way I can know these things is to fail constantly, which is very time consuming. Welcome to ceramics and life in general. The good news is, you've found the right place. There are many friendly knowledgeable folks here that are more than happy to help you along. The key in all of this is patience, especially if self taught. Keep a firing log so you know what works and what doesn't. A log is a great tool that will let you know when your kiln needs attention. For everything else, there's this place. Link to comment Share on other sites More sharing options...
glazenerd Posted August 31, 2016 Report Share Posted August 31, 2016 I have four Paragons: rather fond of them actually. HOWEVER; the first thing I do after running a seating (elements) firing empty: is to a do a calibration firing. I place the normal number of shelves in the kiln, and one test tile on each to check zone variances. Most importantly, I have anywhere from 10-15 cones placed around at various places to check for hot and cold spots. I program to 2232F exactly, run a medium glaze fire program and check it with a pyrometer from 1200-1800F. When cooled, I check the cones, check the tiles: and calibrate according to the readings.All have programmable controllers: and I have done 15-25F TC offset calibrations every time and on all four. All ran way cooler than the readout. I get the frustration: but the advice given to you thus far is spot on. One of the hardest things to admit is operator error ( been there and done that.) You cannot draw any conclusions about reactions of glaze or clay until the kiln is operating within designated limits. Not trying to discourage you: Nerd Link to comment Share on other sites More sharing options...
neilestrick Posted August 31, 2016 Report Share Posted August 31, 2016 If your firing normally takes 20-24 hours, then you're either firing much slower than you need to, or there's something wrong with the kiln. Are you using your own custom program, or one of the pre-programmed settings? Does that time include a preheat? Like Pugaboo said, you should be bisque firing to cone 04. Your cone 5 clay will probably work fine at cone 6. There's a small chance you'll get some bloating, but most likely not. Link to comment Share on other sites More sharing options...
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