Julie P Posted November 20, 2021 Author Report Share Posted November 20, 2021 Not evaporation. I took a sample and added more water but that crumbled on the test tile because there was too much water. The SG will be the same because it is just the base glaze with 1% CoCO3, so no change in the water:solids ratio. I have had a useful suggestion from someone on Glazy who seems to understand the chemistry that it might be the batch of CoCO3 so I am going to thoroughly wash a measured sample and see if that makes any difference. Will report back Link to comment Share on other sites More sharing options...
Min Posted November 20, 2021 Report Share Posted November 20, 2021 On 11/20/2021 at 6:00 AM, Julie P said: I have had a useful suggestion from someone on Glazy who seems to understand the chemistry that it might be the batch of CoCO3 You had that suggestion here also. 4th post from your first one. Hence my suggestion and request for someone else to mix up a small test batch. edit: @Jeanetta recently had a colour issue with a glaze containing a new batch of cobalt carbonate, this thread. I wonder if there is a recent supply of cobalt carb that had incomplete processing and/or contamination. I don't know how many facilities there are that process cobalt ll acetate into cobalt carb. Link to comment Share on other sites More sharing options...
Beebop Posted November 21, 2021 Report Share Posted November 21, 2021 I had this happen to a glaze once too. It was a kaki recipe I made up, I was very perplexed and still am, but I thought it could have been too much bone ash flocculating the glaze. Maybe that combined with some other factors, not sure, but it didn’t include zinc or cobalt. I guess I’m just wondering, is there any chance you could have used bone ash by mistake instead of whiting or dolomite? Link to comment Share on other sites More sharing options...
Julie P Posted November 21, 2021 Author Report Share Posted November 21, 2021 no - definitely no bone ash in this glaze. I also have a kaki glaze with bone ash but haven't had that problem with it. It really looks like we get odd batches of materials at times. Link to comment Share on other sites More sharing options...
Jeanetta Posted December 10, 2021 Report Share Posted December 10, 2021 Interesting indeed. Thanks @Minfor making the connection - I wonder !!! im doing another firing this week with my blue… fingers crossed i don’t get more of this weirdness ! Link to comment Share on other sites More sharing options...
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