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Hello, I am a new member (and new to pottery in general) and have struggled to find the answer to the glaze defects I have been experiencing on previous posts in this forum. I am having trouble with pinholing/pitting/airbubbles (not sure exactly what to refer to it as). Most of my glazed pottery either has loads of little holes (this is especially bad with black underglaze topped with clear) or lots of tiny bubbles trapped beneath the surface. To provide a background, the clay I have been using is Scarva Earthstone ES5 Original White Stoneware Clay, which has a firing temperature of 1200-1290°C and some grog in. I have primarily been using Amaco velvet underglaze, which I apply on cone 04 bisqueware and top with Amaco clear gloss (HF-10), before firing to cone 6 on slow. I only use the standard programmes on my little Skutt Firebox as I have not figured out setting up my own yet (i.e. with soaks). Using tips from previous posts, I have tried wet-sanding bisque fired pieces before glazing, and making sure they are washed and dust free. I have also experimented with slow firing vs medium. The sanding helped a lot and I have fewer pinholes now, but am still getting loads of tiny little pits on (specifically) the black underglaze. I am not sure why this is different to the other colours or clear gloss over bare stoneware (but this still has lots of airbubbles underneath, they just aren't breaking the surface). I have attached some close-up photos of the issues, which hopefully are good enough quality to be visible. I am not sure what is causing this and would be really grateful if anyone has any ideas? Thanks, Ellie
Please help!! I have been using all commercial bisque and commercial underglazes (duncan and mayco) with duncan pure brilliance dipping glaze for several months now with mostly good success. This latest piece is troubling and I am not experienced enough to know what the problem is or how to fix it. Please see the attached photos. The black lettering is not "attached" to the body of the piece in a few areas and there seems to be tiny clear bubbles laying on the surface of only the black lettering. Also, the colored glaze is cracked in places, but only near the lettering... A few other side notes that may be helpful to know. #1--I attached a picture of the pyrometric cones used during this firing. The curved tip indicates that the kiln fired hotter than cone 06, correct? Is this what caused the problem? If so, how do I correct it? #2--The Pure Brilliance Dipping glaze is supposed to have a viscosity of 19-24. I was getting a 16-17. I'm pretty sure I accidentally introduced water to the glaze when wiping down the sides of the container with a sponge. I will try to siphon some of the water out, but could this lower viscosity level be the problem. #3--I had several other pieces firing at the same time and all of them turned out okay. Could the problem have been the thickness of the black underglaze applied? I am truly hoping one of you can help me, but I am also interested in other resources for troubleshooting, so I don't have to bother people. I would welcome recommendations of all kinds--books, websites, etc...