MindyKay Posted October 13, 2020 Report Share Posted October 13, 2020 Hi all! A few months ago, I had very mysterious thing happen to me with a few glazes. (A black glaze turning blue down the middle). After fixing the kiln, I do not think the kiln was ever the issue. I've been looking into it a lot more, and found a phenomenon called Boron-Blue. However, the gloss glaze I'm using doesn't have a lot of boron. Despite this, the frits I'm using are mostly made up of SiO, and CaO. I was reading about Boron Blue on digital fire, and did a little bit of testing. (I have to re run the test for any conclusions, but the results are not why I'm bringing this topic up.) My question is, even though a frit could have little boron, would large amounts of SiO, CaO and slow cooling still contribute to a transparent glaze turning blue? (Granted this glaze is also tinted with a little bit of manganese black stain to make it a grey.) Since I'm in the ceramic tile industry, our methods are a little different, but somewhat the same in theory - especially chemistry wise. Here is some information about the frits I'm using, and the formula. SiO2 Al2O3 B2O3 Na2O CaO MgO Frit 1 64 7 - - 13.5 2 Frit 2 44 2 9 3 5 - Kaolin - 8% Frit 1 - 60% Frit 2 - 22% Zinc - 4% Silica - 7 % Overall, I'd like to just discuss, and maybe learn something that I didn't know before! Outside looking in! Link to comment Share on other sites More sharing options...
liambesaw Posted October 13, 2020 Report Share Posted October 13, 2020 Looks like it has plenty of boron, but could it be the stain? Most black stains contain cobalt as well as manganese and others. Link to comment Share on other sites More sharing options...
MindyKay Posted October 13, 2020 Author Report Share Posted October 13, 2020 I had our supplier give us a stain that didn't have any cobalt in it. Link to comment Share on other sites More sharing options...
neilestrick Posted October 13, 2020 Report Share Posted October 13, 2020 A photo would help make it easier to understand exactly what you're describing. Link to comment Share on other sites More sharing options...
Babs Posted October 13, 2020 Report Share Posted October 13, 2020 @MindyKay I am remembering a thread on this topic earlier, tile business, tiles turning blue...same business? Link to comment Share on other sites More sharing options...
Dick White Posted October 13, 2020 Report Share Posted October 13, 2020 Direct copy and paste from the Mason Color Works FAQ: WHEN I USE BLACK STAINS TO MAKE GREY SHADES THEY TURN GREEN/BROWN/BLUE/PINK ETC. WHY ARE THEY NOT SIMPLY GRAY? Do not use black stains to make gray shades by using small amounts in the glaze. Blacks are made of combinations of cobalt, iron, nickel, chromium, manganese, etc. If low percentages are used, the resulting color is often that of the predominant oxide in any particular black pigment. Care should be taken to use the correct glaze chemistry to avoid combinations that create color problems. It is better to use the gray pigments that we offer. Link to comment Share on other sites More sharing options...
Babs Posted October 13, 2020 Report Share Posted October 13, 2020 3 hours ago, MindyKay said: I had our supplier give us a stain that didn't have any cobalt in it. https://community.ceramicartsdaily.org/topic/22652-production-kiln/?do=findComment&comment=183829 Link to comment Share on other sites More sharing options...
MindyKay Posted October 15, 2020 Author Report Share Posted October 15, 2020 On 10/13/2020 at 5:19 PM, Dick White said: Direct copy and paste from the Mason Color Works FAQ: WHEN I USE BLACK STAINS TO MAKE GREY SHADES THEY TURN GREEN/BROWN/BLUE/PINK ETC. WHY ARE THEY NOT SIMPLY GRAY? Do not use black stains to make gray shades by using small amounts in the glaze. Blacks are made of combinations of cobalt, iron, nickel, chromium, manganese, etc. If low percentages are used, the resulting color is often that of the predominant oxide in any particular black pigment. Care should be taken to use the correct glaze chemistry to avoid combinations that create color problems. It is better to use the gray pigments that we offer. Oh wow! We aren't using Mason exclusively, so I had no idea! Link to comment Share on other sites More sharing options...
MindyKay Posted October 15, 2020 Author Report Share Posted October 15, 2020 On 10/13/2020 at 6:12 PM, Babs said: https://community.ceramicartsdaily.org/topic/22652-production-kiln/?do=findComment&comment=183829 Hi Babs, yes. I'm a little embarrassed to keep on about this topic, but I don't know what else to do other than fiddle with the chemistry to see if I can correct it. As Dick just posted, it could absolutely be my problem, but our material supplier hasn't told me about the possibility of it turning any color other than black. I don't think they have a grey stain, although Mason color is not out of my realm of places to purchase from. Link to comment Share on other sites More sharing options...
Babs Posted October 15, 2020 Report Share Posted October 15, 2020 So you are going for a black stain to get grey. There are grey glazes oug there... I guess you are using one glaze and many stains for uniformity Only posted your initial post as others may take time to write same thoughts on what you already have. Link to comment Share on other sites More sharing options...
Mark C. Posted October 16, 2020 Report Share Posted October 16, 2020 very non tech answer-your face is light colored -hold your breath for longer than you can and walla you turn blue stains not needed. Link to comment Share on other sites More sharing options...
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