Rex Johnson Posted June 26, 2012 Report Share Posted June 26, 2012 A weird thing happened the other day. Using some Coyote cone 5 glaze and Laguna cone 5 B-mix clay. Also had a few pices with their cone 10 "woodfire" body. Anyhow, I glazed the inside of a few bisqued pieces. The body is very white. Something happened I've never seen before. I could see the moisture of the glaze showing through to the outside of the pieces. The only reason I mention this is that I was using a new glaze, and had some iffy results, mostly crawling (bare spots) this time around. But some pieces were glazed with the same cone 5 clear from Laguna I used successfully before, ad they crawled... Not sure what went on here. Bisque was at cone 05 as usual. Maybe not bisqued hot enough? The cones were all down, and I soaked it a good 30-40 minutes before shut down. FYI, my studio is outdoors. the bisque pieces had sat on the shelves fore a week or so but I did try and make sure they didn't have dust on them. I'm all ears... Link to comment Share on other sites More sharing options...
neilestrick Posted June 26, 2012 Report Share Posted June 26, 2012 So after firing the glaze had come through the body? Is that what you mean? Or was the moisture just visible after applying the glaze, before firing? If you bisqued to cone 05 and then soaked for 40 minutes, you probably got to cone 03. But that's still within the acceptable range for bisque.... Link to comment Share on other sites More sharing options...
Rex Johnson Posted June 26, 2012 Author Report Share Posted June 26, 2012 I need to clarify. First point was after bisque at cone 05 I glazed and could see the moisture thu the wall of the piece(s). Second (and possibly related) point was I had a lot of crawling I don't normally get. I have no idea if one has anything to do with the other... It was just odd to see the moisture coming thru the pot. Never seen this before. Link to comment Share on other sites More sharing options...
neilestrick Posted June 26, 2012 Report Share Posted June 26, 2012 When pots are thin, the wall of the pot can be easily saturated by the water in the glaze, and show through on the other side. If the piece is too thin and totally saturated during glazing, it can cause the glaze to crawl. Might not be the reason for the crawl, but I think there's a good chance it is. My students are obsessed with making thin pots, but I always remind them that too thin can make glazing difficult. The pot must be thick enough to absorb all the water present in the glaze during glaze application. In my studio we dip the glazes. If the pot is too thin, it can't take in enough water, and the glaze will be too thin. Plus it takes forever to dry or even starts to run off if it can't dry fast enough due to the pot being saturated. Link to comment Share on other sites More sharing options...
Rex Johnson Posted June 26, 2012 Author Report Share Posted June 26, 2012 I do try to throw thin(ner), but rarely am able due to my 're-skilling' after many years away from production throwing, and many years older... I did notice that the glazes were quite thin when mixed to spec using a hydrometer. That said, I didn't let the glaze set 24 hours as recommended. Maybe that was the problem. As far as thin pots, these where no less than previous pots. Seeing the moisture come thru the wall gave me to think (besides a thin glaze) that maybe the bisque was off, and they lacked density. Link to comment Share on other sites More sharing options...
Woody Sheep Posted June 27, 2012 Report Share Posted June 27, 2012 Hi. You are not bisque firing hot enough. I use the Laguna B-mix and I had a similar problem, but it was with excessive pinholing. I finally solved it by bisque firing to cone 3 and glazing at Cone 6. (Yes, this cone 10 clay works great at Cone 6) It seems excessive, but it tested all the way from cone 05 up and finally got the pin holes to stop at bisque cone 3. Link to comment Share on other sites More sharing options...
StefanAndersson Posted June 27, 2012 Report Share Posted June 27, 2012 Hi. You are not bisque firing hot enough. I use the Laguna B-mix and I had a similar problem, but it was with excessive pinholing. I finally solved it by bisque firing to cone 3 and glazing at Cone 6. (Yes, this cone 10 clay works great at Cone 6) It seems excessive, but it tested all the way from cone 05 up and finally got the pin holes to stop at bisque cone 3. Sounds like you got a good solution. I can surly see why this would be and many clays have this problem more or less. If the pinholes appear directly after glazing you have a solution but if they appear first during the firing an option could be to fire the glaze kiln slower in the cone 05-1 range to fire out the organic material creating the holes. With the crawling it really sounds like the oversaturation is the problem. I have that problem on raw glazed pots if the glaze if applied to soon. Lowering the amount of water in the glaze and bisquing higher is a option if the glaze doesn't become to thick. Another option is to bisque lower if the pieces doesn't fall apart when glazing. Link to comment Share on other sites More sharing options...
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