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Showing results for tags 'dark clay'.
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Hello helpful potters! I need help with an 04 bisque firing schedule. I'm having problems with pinholing in the 266 Standard Ceramic cone 4-6 dark brown clay that I'm using. About 50% of the time I'm getting a few pinholes, generally on the bottom but also on the sides. When I slow glaze, my cone 5 witnesses goes all the way down and the 6s are at about 2:00. The glaze I'm using is Potters Choice for cone 5/6, 3 coats as suggested by Amaco Brent, and this problem is happening pretty much just on the 266 and not the lighter color clays I use. I know pinholing can be a symptom of a variety of things, but I'm ready to try a slower bisque schedule in case they're being caused by gases or other impurities that haven't completely burned out during the bisque. Maybe it should go faster to 1100 and then slower for the next 1000 degrees? Or have a hold in there somewhere? I've tried to work out a schedule myself but it always ends up being about 18 hours long. Here's the cone 04 preset firing schedule I'm using in my LL kiln: 80 per hour to 250 (2 hrs) 200 per hour to 1100 (4 hours) 100 per hour to 1100 (1 hour) 180 per hour to 1676 (3 hours) 80 per hour to 1926 I also add a 10 minute hold at the end. When I use this cycle it tells me the end temp will be 1945 instead of 1926, ( 1926 is what it says on this firing schedule. It does end up at around 1945. I unplug the vent when it's done firing. Any ideas will be greatly appreciated, as would any suggestions about other things I may be doing, or not doing, that could be causing the pinholing. oh also I don't stack my bisque in the kiln. Would stilting the pieces give better air flow or deform them? Thanks! Irene
Turquoise stone and white matte ^6 ox on calico dark red clay. A couple very wonky vases that developed decent sized cracks from uneven drying, this was one of the first things I made after taking a hiatus of 3 years from clay, be gentle! I needed to keep a few unsatisfactory pieces to try my experiments. I am totally head over heals in love with the color combo, but am very sad all the pieces developed pin holes on them... I talked to the professor and she is going to go over how to avoid that next time and keep my work together as to have a more consistent firing.