Sabbir Posted December 20, 2019 Report Share Posted December 20, 2019 Hi, i am new here and also new in ceramics industries, recently i have finished my graduation on ceramics Engineering, after joining my first job i saw that there have main problem is micro pin hole on glaze which only show when light reflect on it. Already i checked something : 1. Test all material to find out problematic material but i do not find anything. 2. Checked firing temperature also but three had no problem also 3. We used in glaze, zirconium, zinc, k feldsper, soda feldspar, quartz, calcium carbonate, talc, china clay and cmc. how can i move on next step, Please help me.. Link to comment Share on other sites More sharing options...
liambesaw Posted December 20, 2019 Report Share Posted December 20, 2019 Is there a way you can try substituting the calcium carbonate with a non carbonate source of calcium like wollastonite? I think a good goal is to limit the loss on ignition of all ingredients so that bubbles don't form in the glaze to begin with. Link to comment Share on other sites More sharing options...
Bill Kielb Posted December 20, 2019 Report Share Posted December 20, 2019 2 hours ago, Sabbir said: Hi, i am new here and also new in ceramics industries, recently i have finished my graduation on ceramics Engineering, after joining my first job i saw that there have main problem is micro pin hole on glaze which only show when light reflect on it. Already i checked something : 1. Test all material to find out problematic material but i do not find anything. 2. Checked firing temperature also but three had no problem also 3. We used in glaze, zirconium, zinc, k feldsper, soda feldspar, quartz, calcium carbonate, talc, china clay and cmc. how can i move on next step, Please help me.. Pinholes! A vexing problem for sure. It would be great to know if the pinholes originate as a result of the Claybody so do these pinholes only form on a specific body and not others using the same glaze? Some information you may want to include:: What cone is this fired to? What firing schedule? What Claybody are you using? What is the specific glaze formula so it can be analyzed. What have you tried and what were the results? The more information you can provide the more likely you will get informed opinions here. Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted December 20, 2019 Report Share Posted December 20, 2019 I have several comments (but no solutions): Bubbles (and "pin holes") can occur from multiple situations; some examples: due to application technique, glaze recipe ingredient choices, firing time temperature profiles, kiln atmosphere First read carefully Mr. Xiong's thesis, and the references therein, before jumping to conclusions on the why your glaze has almost invisible bubbles. Bubbles (and "pin holes") can occur from multiple situations. citation: Xiong, Liping. "Glaze Surface Tension Effects on Bubble Evolution". Master of Science (M.S.) Theses., Alfred University. Faculty of Ceramic Engineering. Kazuo Inamori School of Engineering. 2004. http://hdl.handle.net/1951/25193 Mr. Xiong addresses some of the multiple situations and should provide you leads to other useful literature sources. The surface tension and the viscosity properties of the glaze melting profile are key variables. High values of mean that at your firing temperature the ability of the melt to move is impaired, otherwise the glaze would move into the open space. The glaze ingredients implies that the viscosity of the glaze melt could be quite high. High viscosity melts and/or with high surface tension can produce bubbles and pinholes. Are the 'pin holes' dimples in the glaze surface, or are they suspended bubbles in the glaze, or are they open passage ways from the outer surface of the glaze to the ceramic substrate? If the holes are cleanly open from the glaze surface to the ceramic substrate, I would rate application and substrate surface higher than gas formed from carbonate decomposition. From my experience in problem solving the first step is to completely identify the problem before trying to develop a solution. Some questions to chase: Where are the 'pin holes' (PH) located on the ware? are the PH uniformly distributed in the glaze, or are they in specific patterns or locations? Are the PH all the same size, color, shape. Do the PH occur all the time, on all items, in all application thickness, in all firings, on all clay bodies? Where are the PH not found? One needs to have data on these where and when questions to understand the why question that will provide the action(s) that will solve the PH problem. LT Link to comment Share on other sites More sharing options...
Min Posted December 21, 2019 Report Share Posted December 21, 2019 @Magnolia Mud Research, that was an interesting read, thanks for sharing the link. Couple comments after quickly skimming through it, firstly I have to question if the area of further research (insofar as the op's situation) regarding the addition of 0.5% Molybdenum trioxide for the purpose of clearing bubbles is really relevant? Have you ever seen a ceramic glaze recipe that includes this for this purpose? Secondly, I wasn't keen on his research pointing to raising the RO:R2O by the addition of PbO at the expense of Na2O and the resultant decreased population of bubbles as being a safe viable solution. I agree we need more info before trying to figure the cause for the pinholes for the op. Link to comment Share on other sites More sharing options...
Hulk Posted December 21, 2019 Report Share Posted December 21, 2019 Curious, any correlation thickness - of clay, the piece - and incidence of pinholes? Looks like there's a discolored zone where the pinholes are, in the pic. Is that true? If so, describe the discolored zone? How is the piece cleaned before glazing, is the glaze coat even, no bubbles or holes, if there are bubbles/holes, how are they fixed up before firing? Any wax resist used in the process? Link to comment Share on other sites More sharing options...
Sabbir Posted December 22, 2019 Author Report Share Posted December 22, 2019 @Magnolia Mud Research thank you, already i tried to find out this orgin of problem, all type of product showed this type of ph, this is micro ph, if you see this with out extra light you can not find it, when light reflect on it You can see that all bodies have thousand of micro pin holes. Generally our firing temperature 1200 degree celcius, already increased temperature but same result, we had two kiln one is tunnel kiln &another is shuttle kiln i tried both kiln but same result, if you have any opinion about it you can share me. Link to comment Share on other sites More sharing options...
Sabbir Posted December 22, 2019 Author Report Share Posted December 22, 2019 @Hulk actually this picture did not show accurately, there had thousand of micro pin hole, which Are not possible to capture, thickness of ware not matter here, if you have any idea you can share with me. Thank You. Link to comment Share on other sites More sharing options...
neilestrick Posted December 22, 2019 Report Share Posted December 22, 2019 It's interesting that the pinholes are essentially occurring in a line, which may mean that there's something going on in the clay body or glaze application in that area. Link to comment Share on other sites More sharing options...
Hulk Posted December 22, 2019 Report Share Posted December 22, 2019 Ahh, so the pinholes are everywhere! Tony Hansen has a detailed article on the subject http://digitalfire.com/4sight/troubleshooting/ceramic_troubleshooting_glaze_pinholing_pitting.html ...you might try halving the problem space - is the problem related to the clay, the glaze, or both? Ideally, the problem has one (main) cause, not many - any road, Tony Hansen makes a case for firing balls of glaze (he rolls up glaze into a ball after drying it out some on a plaster bat) https://digitalfire.com/4sight/glossary/glossary_melt_fluidity.html He uses fancy ramps (very cool!); see also the ten gram balls that he sets on porcelain test tiles. You might try firing test balls on different clay test tiles - is the problem related to the clay? And from there, adjusting the glaze and/or firing... Link to comment Share on other sites More sharing options...
Hulk Posted December 22, 2019 Report Share Posted December 22, 2019 3 minutes ago, neilestrick said: It's interesting that the pinholes are essentially occurring in a line, which may mean that there's something going on in the clay body or glaze application in that area. Aye, that's what I'm seeing, however, I believe op says the pinholes are everywhere? Link to comment Share on other sites More sharing options...
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