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Showing results for tags 'pitting'.
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
I've been having problems with pitting in glazes lately and am wondering is it good practice to fire an empty kiln to burn off any potential lingering fumes to help glazes? Have been firing non-stop with about 2 months now, and in the last few weeks a lot of work is coming out of the kiln with pits. Have been in touch with my clay and glaze supplier and they are stumped! Have tried many firing schedules, from slow to fast, with up to 45min soaks at top temp and tried a drop and hold schedule but nothing seems to work. Have also tried bisque firing high to 1020oC with a 45min soak at 780oC on the way up and 45min at top temp but no success. It leaves me wondering should I fire an empty kiln, and would that "freshen up" the atmosphere within? Could the bricks be holding onto residual fumes from firings and could this be causing the glaze issue? I have an extraction fan that runs for the full firing until the firing is finished. And allow the kiln to cool naturally with the fresh air valve closed (as per operational instructions). Any advice would be much appreciated. Thanks in advance.