kevinmansfield Posted January 18, 2014 Report Share Posted January 18, 2014 Hi Folks, I recently asked a question about my crazing problem using Duncan Envision Glazes. I was advised to try firing at Cone 05 instead of my usual 06 and then slow down the cooling. Unfortunately I have always fired at Cone 06 for my bisque firing and glaze firing and it is only recently I have had the crazing issue. My worry is how the things in the kiln will react. Will I get any warping? Cracking? Or other problems with the bisque? Problems with the glaze?I tend to use Mayco Stroke and Coat, which says fire to Cone 06 on the bottles and Duncan Envision together on earthenware clay. Many thanks in advance, Kevin. Link to comment Share on other sites More sharing options...
bciskepottery Posted January 18, 2014 Report Share Posted January 18, 2014 Many folks working at earthenware temperatures will bisque one cone higher than their glaze temperature. The higher bisque removes more impurities. With a lower glaze, you get less chance of off-gassing from the claybody that can't escape the glaze cover. Maybe try bisque at 05 and glaze at 06. Link to comment Share on other sites More sharing options...
neilestrick Posted January 18, 2014 Report Share Posted January 18, 2014 I would bisque at 04, and glaze anywhere from 06 to 04. Fire you glazes as hot as they can handle without running too much. Most low fire glazes handle 05 just fine, and many can go to 04. Link to comment Share on other sites More sharing options...
Benzine Posted January 18, 2014 Report Share Posted January 18, 2014 In my classroom, I bisque at 04, glaze at 05. I haven't had any issues with glaze defects. Sometimes the glazing comes out looking somewhat bland or even hiddeous, but that may be an application issue on the part of the maker....... Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 18, 2014 Report Share Posted January 18, 2014 I've said this one a million times on the forums............ One of the things that you can never get around in studio ceramics is the need to "test, test, test". There are so many variables involved in any given situation that the only way to know for certain is to try it (and try it repeatedly to verify results). best, .................john Link to comment Share on other sites More sharing options...
Pres Posted January 18, 2014 Report Share Posted January 18, 2014 Years ago, I was doing low fire (^06) earthen ware. We were using Amaco glazes at the time. I had always bisqued to ^06, and did then. I had been glaze firing to ^06 also, but found that some of the glazes did not seem to be quite right, and some had some crazing problems. I also noticed that I had a problem with some pin holing on some glazes. I decided to try different firing cycles, and tested with many witness cones. After all was said and done, I decided to move to ^05, and be cognizant of which glazes needed higher temps and which were in need of cooler ones. The Amaco glazes used to say 05-06 and I believe that was for ease of labeling as not all of them are 06. Best bet is to become very familiar with your kiln, and with your glazes. Link to comment Share on other sites More sharing options...
kevinmansfield Posted January 19, 2014 Author Report Share Posted January 19, 2014 Many thanks for the replies. I usually fire my bisque and glaze firing together. Will I have any problems if the glaze firing is a higher temperature than the bisque firing? I say this because I have several tiles which I have already bisque fired to Cone 06 and glazed, would it be dangerous to fire these to Cone 05 now? My goal is to eliminate the crazing which I have experienced on my last couple of firings using Duncan Envision glazes and I was advised to try a Cone 05 firing. I currently hold the temperature 998º for 10 minutes, could it be worth holding for longer? Link to comment Share on other sites More sharing options...
Benzine Posted January 19, 2014 Report Share Posted January 19, 2014 I used to fire my class kiln , with both greenware and glazed bisqueware together. I don't do this now, if I can avoid it, because it seems that every time I try, something is thicker than it seems, or has an unknown void, which haven't dried, and I end up with bits of bisqueware stuck on the glazed projects. Annnnnnyway, you would not have an issue refiring those tiles. I've refired projects multiple times, to get the glaze to turn out better. I will say, the last firing, a stress crack did appear, so there are limits. In regards to holding, I wouldn't think this would help with crazing, as crazing has more to do with the glaze fit. So instead of holding, you'd be better off slowing the cool down. The only way to know for sure, is to do what John recommended; test, test, test. Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 19, 2014 Report Share Posted January 19, 2014 FYI....... some low fire glazes are sensitive to the gases given off from bisquing clay (like sulphur dioxide) and it can cause glaze defects. best, ..............john Link to comment Share on other sites More sharing options...
Pres Posted January 19, 2014 Report Share Posted January 19, 2014 Ditto on what John just said. I never fired the two firings together in those days. Most glazes at the lower range are sensitive to gasses from the bisqueware. Yellows, reds and oranges in particular. It can also effect the blues to some degree making them a little less clean. Link to comment Share on other sites More sharing options...
NancyAmores Posted January 21, 2014 Report Share Posted January 21, 2014 Hi Kevin, I probably should have mentioned that I have noticed a slight color change at 05 with the Envisions, they tend to darken. These glazes don't move at all, even at 05, and I haven't had any problems with warping or cracking on either a white talc based body (Laguna #10-T). I used a cooling ramp of 250F to 1500F but I'm still testing to see if I can speed that up and get the same results. Link to comment Share on other sites More sharing options...
Carrick Posted February 25, 2019 Report Share Posted February 25, 2019 As a newbie I stick to 04 to bisque and 06 to glaze fire on earthenware clay . Never had any problems in my electric kiln . love reading all feed back from a wealth of experienced potters. thank you Link to comment Share on other sites More sharing options...
Jodi Posted January 5, 2020 Report Share Posted January 5, 2020 I am a rookie Potter. I make baby hand and footprint impressions. I have been using Laguna -Miller 110 clay. I have been firing my greenware to cone 6. I also fire my glazed bisque to cone 6 and have been using primarily Duncan Envision. My last fire (glazed bisque) I had 2 of my handprints crack starting at the edge and about 1 inch all the way through. I have an older manual kiln (and it has thus far worked perfectly). My glazed pieces were positioned in the kiln very close to the heating coils. Would that have caused them to crack? I was going to attempt to repair them by using WareRepair then glaze over it and refire. I have reglazed and refired pieces before when my glaze wasn’t even. It has worked beautifully so far. I have found it’s hard to disguise a crack trying to fix it the “ceramic way” - rather than , for example , filling the hairline crack with gorilla glue then using an extra fine sharpie at just the right color to cover the crack and use a touch of high gloss clear nail polish gel to add back the gloss. Any suggestions?? The cracks are too thin to add crushed bisque mixed with anything. Will the Ware Repair fill in the crack or just melt out? Thanks Link to comment Share on other sites More sharing options...
Mark C. Posted January 5, 2020 Report Share Posted January 5, 2020 All of theses products -Marks ware repair or amaco bisque fix all can work-Marks ware reapair is more fluid than all other like products-They all will leave a mark of a different color so glaze need to cove them-They will NOT run out as you mentioned . Testing is the only way to know for sure about color matching-again use glaze over them to cover the non colora match. I have used them for years and thats the olny way to learn what they do and how they look. Glue and markers is not a valid way to fix an item for anyone unless its for yourself. Link to comment Share on other sites More sharing options...
Louise H Posted October 11, 2020 Report Share Posted October 11, 2020 I have been using Duncan Envision glazes and they are driving me nuts! Initially, they were amazing - true colour - great for my students. Now they are crazing! Like crazy - all of my sculptures will come out of the kiln fine and then sometimes within hours sometimes months later they start crazing! I also ended up with mini meteorites shooting everywhere with a purple glaze. I have never experienced this problem in 28 years of firing. I have fully programmable kiln and I make sure pieces are fully cool before removing. Is this a problem with the Duncan glazes? Link to comment Share on other sites More sharing options...
Bill Kielb Posted October 11, 2020 Report Share Posted October 11, 2020 On 1/18/2014 at 5:59 AM, kevinmansfield said: only recently I have had the crazing issue Crazing is generally a glaze fit issue with the claybody where the coefficient of expansion differs. Firing to a different cone may change the COE of your claybody enough. Assuming the glaze has not changed any chance the claybody has? Just thinking here, do all variety’s of Envision craze or is it limited to several? Link to comment Share on other sites More sharing options...
Hulk Posted October 11, 2020 Report Share Posted October 11, 2020 Hi Louise! Good news (might be) that it takes a while for the crazing to manifest - indicates slight misfit (as opposed, say, to an immediate bb sized craze pattern). Any road, if you're using the same glazes (not new bottles), same firing pattern, but new bag(s) of clay, look to the clay. Hopefully, there's only one new factor to look into... Link to comment Share on other sites More sharing options...
Min Posted October 11, 2020 Report Share Posted October 11, 2020 10 hours ago, Louise H said: I also ended up with mini meteorites shooting everywhere with a purple glaze. Can you post a picture of this? Lime pops or shivering? Link to comment Share on other sites More sharing options...
Iraima Posted December 22, 2020 Report Share Posted December 22, 2020 On 10/11/2020 at 9:10 AM, Min said: Can you post a picture of this? Lime pops or shivering? Link to comment Share on other sites More sharing options...
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