Skye Jordan Posted October 17, 2021 Report Share Posted October 17, 2021 Hi, I'm using speedball underglazes. To thin them out, I added a little water and a tiny electric whisk, then replaced them in their bottles. But when I went to use them, they come out gritty and uneven. When I go thin and layer, i get a buildup that easily flakes off. Suggestions? Thanks, Skye Link to comment Share on other sites More sharing options...
neilestrick Posted October 17, 2021 Report Share Posted October 17, 2021 46 minutes ago, Skye Jordan said: Hi, I'm using speedball underglazes. To thin them out, I added a little water and a tiny electric whisk, then replaced them in their bottles. But when I went to use them, they come out gritty and uneven. When I go thin and layer, i get a buildup that easily flakes off. Suggestions? Thanks, Skye What colors? The brown is known to be gritty, but that's the only color I've run into that has that problem. Are they very old? How many layers are you applying, and at what stage is the clay? Link to comment Share on other sites More sharing options...
Pres Posted October 17, 2021 Report Share Posted October 17, 2021 Used the speedball's years ago. Some of them did seem quite gritty, so I tried a mortar/pestle solution. I ground them while wet, and the sieved them. Much smoother. Another thing you have to be careful with after mixing them is not to allow them to freeze, that causes some changes in consistency and adds to the grittiness. best, Pres Link to comment Share on other sites More sharing options...
Min Posted October 17, 2021 Report Share Posted October 17, 2021 1 hour ago, Pres said: Some of them did seem quite gritty, so I tried a mortar/pestle solution. Really would not recommend grinding any underglazes that contain cadmium inclusion stains. I contacted Speedball many years ago and asked for a list of which underglazes contain cadmium stains, there were quite a few that did. Can't get my hands on the list right now but I remember it included melon, yellow(s), orange(s), purple(s), red(s) and pink. Their product line has expanded since then so it's probably safe to say there are more than those ones now. If you grind stains that contain cadmium the stain will no longer be stable and cadmium release would be expected. The Safety Data sheet from Speedball isn't very clear on this. Just a brief mention of it here and there but not specific to each colour. If you do consider grinding (or any other mechanical process that could degrade the stain integrity) I would contact Speedball first and confirm whether cadmium stains are used in each particular underglaze in question. https://www.speedballart.com/customer-service/ Link to comment Share on other sites More sharing options...
Pres Posted October 17, 2021 Report Share Posted October 17, 2021 Thank you Min for correcting me. In the day, it was something we did not often check as the information was not readily available as it is today. That said, I would not endorse the grinding of the underglazes, unless one can confirm that there is no cadmium or other harmful materials bound in the substrate. Thanks again for pointing these facts out @Min best, Pres Link to comment Share on other sites More sharing options...
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