docweathers Posted February 15, 2015 Report Share Posted February 15, 2015 From time to time I'm having problems with Stephen Hill's watercolor green pitting. It's not as bad when I put it over SCM. Sometimes it's just fine. In all cases, I'm using G mix 6 w/ grog Fired to cone 6. All the results are from the same small batch of glaze. This is the formula that I'm using Water Color Green (Cone 6) Custer ... 47.8 Silica ... 16.9 Lithium Carb ... 4.0 Frit 3124 ... 5.0 Whiting ... 16.0 Strontium Carb ... 7.5 Bentonite ... 2.9 Copper Carb ... 8.0 As a side note, on one pot the pitting actually looked pretty cool since it was very evenly distributed and the color was darker around each pit. Not what I would have planned but an interesting result. Link to comment Share on other sites More sharing options...
TJR Posted February 15, 2015 Report Share Posted February 15, 2015 It's probably your clay body. If you are using a coarse clay is it pitting along your trimming line? You could also have dust on your bisque ware. Or you are firing your kiln too fast. TJR. Link to comment Share on other sites More sharing options...
Babs Posted February 15, 2015 Report Share Posted February 15, 2015 Need a slow down and soak towards the end?? Got any pics? Link to comment Share on other sites More sharing options...
docweathers Posted February 15, 2015 Author Report Share Posted February 15, 2015 Actually the rim is one of the least. areas. Given the distribution of the pits and it's intermittent appearance, I think it's very likely that it's from dust on the bisqueware. I've probably been pretty sloppy about cleaning things off before glazing. I am firing pretty slowly with slow cooling... Jon Britt's E3 schedule. I'm hesitant to post pictures, unless it is critical, since last year I ran over my quota and could post no pictures. Link to comment Share on other sites More sharing options...
docweathers Posted February 16, 2015 Author Report Share Posted February 16, 2015 I wonder if there's a way to actually use this dust caused pitting in a decorative way. Rather than studio dust could one seed the pits with particles of colorant? Link to comment Share on other sites More sharing options...
TJR Posted February 16, 2015 Report Share Posted February 16, 2015 After you bisque, sand your work with coarse sand paper. Then dip your pieces in clean water. Let dry a day. The sand will collect in the bottom of the bucket. you can put it back in your reclaim clay bucket if you wish. that's about it. TJR. Link to comment Share on other sites More sharing options...
neilestrick Posted February 16, 2015 Report Share Posted February 16, 2015 8% copper carb? For real? Link to comment Share on other sites More sharing options...
docweathers Posted February 16, 2015 Author Report Share Posted February 16, 2015 Actually there is a slight inaccuracy. It works out to 7.44% copper carbonate. I Mix at 8% in a looks great. Here's the URL where I got it http://www.lakesidepottery.com/Pages/Glaze-recipes-at-Lakeside-Pottery.htm There are a lot of other nice glazes in that list. Link to comment Share on other sites More sharing options...
neilestrick Posted February 16, 2015 Report Share Posted February 16, 2015 Actually there is a slight inaccuracy. It works out to 7.44% copper carbonate. I Mix at 8% in a looks great. Here's the URL where I got it http://www.lakesidepottery.com/Pages/Glaze-recipes-at-Lakeside-Pottery.htm There are a lot of other nice glazes in that list. I wouldn't use that in functional pieces without testing it first. When you say pitting, do you mean pinholes with rounded edges like a dimple, or sharp edges pits, more like a burst bubble? Link to comment Share on other sites More sharing options...
docweathers Posted February 17, 2015 Author Report Share Posted February 17, 2015 They looks like burst bubbles that didn't heal. Link to comment Share on other sites More sharing options...
neilestrick Posted February 17, 2015 Report Share Posted February 17, 2015 They looks like burst bubbles that didn't heal. In my experience this is due to the glaze being over fluxed. If you check the limit formulas you'll see that it's at the low end of alumina and silica. Try adding equal parts koalin and silica in 1-2% increments. Link to comment Share on other sites More sharing options...
docweathers Posted February 18, 2015 Author Report Share Posted February 18, 2015 That's worth testing. Thanks Link to comment Share on other sites More sharing options...
Babs Posted February 19, 2015 Report Share Posted February 19, 2015 A tried and true glaze, a known clay body, with a tried and true firing schedule in someone else's kiln, someone else's clay eetc. .....may need a slowing and to try a 15min soak at end of firing. This glaze has obviously, or not, matured nicely for someone somewhere under certain conditions so perhaps testing the high end of the firing may negate the need to fix the glaze. That's where I'd be starting. Perhaps.......testing in your own kiln, nothing beats it. Link to comment Share on other sites More sharing options...
David Woodin Posted February 20, 2015 Report Share Posted February 20, 2015 The original glaze on the website you gave makes it difficult to convert because the Bentonite and Copper Carb are usually added as a % later. Therefore your glaze is slightly different than the website. At any rate it will run. should be Custer 49.92 Silica 17.2 Lith carb 4.05 3124 5.06 whiting 16.19 Stront 7.59 Total 99.98 Bent 3.04 Copper Carb 8.09 Link to comment Share on other sites More sharing options...
docweathers Posted February 20, 2015 Author Report Share Posted February 20, 2015 thanks for the correction in the glaze formula. In my digging around to find the source of the pitting i found this article that explains one cause http://http://www.highwaterclays.com/files/Preventing%20Pinholes,%20Blisters,%20Craters,%20and%20Bubbles.pdf Link to comment Share on other sites More sharing options...
Crusty Posted February 20, 2015 Report Share Posted February 20, 2015 Im with Neil, I wouldn't use it on anything I was eating or drinking from... I do like the color though, I been using a lot of greens here lately... Link to comment Share on other sites More sharing options...
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