bluedawg Posted October 18, 2011 Report Share Posted October 18, 2011 I am a beginner and trying to mix a nice variagated turquoise cone 6 glaze. I have tried two different recipes and they both came out gunmetal black. After the first one I thought for sure I did something wrong but now I am wondering if maybe it's something else. My materials are very old... is there a shelf life to carbs and oxides? I attaching a photo of the glaze. You can see it on the top portion of the vase. It kind of breaks green at the edges but you can see where the gunmetal black has pretty much taken over... This is the second recipe I tried (I no longer have the first) : 3) Weathered Bronze Green - Cone 5-6 Lithium Carbonate 50 Strontium Carbonate 1000 Neph Sye 3000 Ball Clay 500 Flint 450 Also add: Copper Carbonate 250 Titanium Oxide 250 Link to comment Share on other sites More sharing options...
Pres Posted October 19, 2011 Report Share Posted October 19, 2011 I am a beginner and trying to mix a nice variagated turquoise cone 6 glaze. I have tried two different recipes and they both came out gunmetal black. After the first one I thought for sure I did something wrong but now I am wondering if maybe it's something else. My materials are very old... is there a shelf life to carbs and oxides? I attaching a photo of the glaze. You can see it on the top portion of the vase. It kind of breaks green at the edges but you can see where the gunmetal black has pretty much taken over... This is the second recipe I tried (I no longer have the first) : 3) Weathered Bronze Green - Cone 5-6 Lithium Carbonate 50 Strontium Carbonate 1000 Neph Sye 3000 Ball Clay 500 Flint 450 Also add: Copper Carbonate 250 Titanium Oxide 250 Is it possible you have it on too thick. I see that where it is breaking at the rim, it is broken green. The other question I have is what the other glaze was, and how high on the pot was that dipped? Link to comment Share on other sites More sharing options...
JLowes Posted October 19, 2011 Report Share Posted October 19, 2011 I have attached a picture of what this glaze looks like fired at Cone 6 oxidation. It is much thinner than your application, so I think Pres may be on to something there. The dark color in my piece comes from a second glaze, Tea Dust, squirted on the Weathered Bronze. I really wouldn't call it a turquoise, and it does have some tannish tones (the bronze I presume). Try again on a smaller piece to see if you can get another result. I wipe off my pot with a wet sponge before dipping in glaze, and don't stay in there too long. John L. Link to comment Share on other sites More sharing options...
JLowes Posted October 19, 2011 Report Share Posted October 19, 2011 I have attached a picture of what this glaze looks like fired at Cone 6 oxidation. It is much thinner than your application, so I think Pres may be on to something there. The dark color in my piece comes from a second glaze, Tea Dust, squirted on the Weathered Bronze. I really wouldn't call it a turquoise, and it does have some tannish tones (the bronze I presume). Try again on a smaller piece to see if you can get another result. I wipe off my pot with a wet sponge before dipping in glaze, and don't stay in there too long. John L. Link to comment Share on other sites More sharing options...
JLowes Posted October 19, 2011 Report Share Posted October 19, 2011 Sorry; I didn't have the how to attach a picture down right on my first try. John L. Link to comment Share on other sites More sharing options...
Lucille Oka Posted October 19, 2011 Report Share Posted October 19, 2011 Try ball milling the ingredients and straining through a finer sieve several times. Link to comment Share on other sites More sharing options...
bluedawg Posted October 19, 2011 Author Report Share Posted October 19, 2011 Thanks! I am going to try all of these these ideas. One question to JLowes... Are you firing oxidation or reduction? I am using an electric kiln, oxidation. The color you have is exactly what I was hoping for. Link to comment Share on other sites More sharing options...
Bobg Posted October 19, 2011 Report Share Posted October 19, 2011 Bluedawg, What's the glaze on the bottom of your pot? I also would suggest thinning the glaze and try it again. Bobg Link to comment Share on other sites More sharing options...
bluedawg Posted October 19, 2011 Author Report Share Posted October 19, 2011 Thanks Bobg, I can't really remember what I mixed for the bottom of this pot. I have since began keeping better notes But I had some pots where the weathered green was not over another glaze and it looked the same.... lots of them in fact I am learning as I go. It's a slow process. Link to comment Share on other sites More sharing options...
Guest JBaymore Posted October 19, 2011 Report Share Posted October 19, 2011 For Cone 6 this glaze formula is WAY oversupplied with SrO flux at 0.47 moles. Also oversupplied with the KNaO fluxes at 0.43 moles. Then you add in the fact that the percentage of copper carbonate addition is pretty high at 5% of the batch weight. The excess of the SrO and the KNaO is going to cause the glaze melt to "attack" the underlying clay body a bit, thereby pulling some of the iron out of the body into the glaze melt. So the amount of disolved metallic coloring oxides is getting on the high side in the melt. Where there is some thickness to the glaze melt, likely the thermal mass of the glaze is keeping it a tiny bit hotter during the cooling cycle than the thinner parts and it is more isolated near the surface of the glaze from any extra alumina picked up from the "attacked" clay body. This is likely retarding the cooling a bit, nor is providing an inhibitor to re-crystalization, and is allowing the heavy saturation of metals (mainly copper oxide) to percipitate out on the surface of the cooling glaze. Hence the black semi-matte surface where thick. The combination of the imbalance of the fluxing oxides and the high percentage of copper says to me to keep this one off of the "working surfaces" of functional ware. Working in its favor to make the glass stronger is the high alumina number and the reasonable silica number. But still rather questionable. 50.00 Lithium Carbonate 1000.00 Strontium Carbonate 3000.00 Nepheline Syenite 500.00 OM #4 Ball Clay 450.00 Flint 250.00 *Titanium Dioxide 250.00 *copper 0.04* CaO 0.05* Li2O 0.01* MgO 0.10* K2O 0.33* Na2O 0.47* SrO 0.01 TiO2 0.57 Al2O3 2.89 SiO2 Take that fired glaze, particularly where black, and place a sample of it into a glass cup that is 1/2 full of vinegar. Place the sample into the glass so that the vinegar covers only about 1/2 of the fired sample. Let it sit there for a few days, replenishing the vinegar as it evaporates. DON'T change the level in the glass! You want that demarkation line where it is in the vinegar and where it is not to remain absolutely constant. Take the test piece out, throw out the vinegar, wash the sample with water, and then dry it off very well. Maybe let it sit for half a day so that the surface is really, really dry. Take a magnifying glass or a loupe and look at the surface where it was immersed in the vinegar and the part that was not. See if you can see surface reflectivity or color changes in the two parts. I'd be surprised if you did not. best, ...................john Link to comment Share on other sites More sharing options...
bluedawg Posted October 19, 2011 Author Report Share Posted October 19, 2011 Thanks John, I have been studying Rhodes "Clay and glazes for the potter" so that level of detail is good for me to hear. It's tough for me to learn at my age, or maybe it was drug use in my younger years, but I am determined to understand... Regarding the vinegar test, What would the surface change indicate? Link to comment Share on other sites More sharing options...
Guest JBaymore Posted October 19, 2011 Report Share Posted October 19, 2011 Regarding the vinegar test, What would the surface change indicate? You are welcome. Those kinds of changes show a number of potentialities. That the glaze surface is being affected by a material whose Ph is in the range of food products. In other words, that substances in the glaze can leach out of the fired "glass" into food stuff. That the glaze might be eroded by stuff like dishwashing cleaners. That the glaze surface is not "stable" and the appearance will change over time. That in installation locations like outdoor sculptures the surface could be affected by things like acid rain and pidgeon poop. And so on. Just becasue something LOOKS like a "glaze" to the eyeball.... does not necessarily mean that it is a "good" glass. And just because the recipe is published somewhere does not mean that the glaze originator knew anything about glaze chemistry. Or that the originator wanted it USED on functional wares. Or that the originator tested it for use in outdoor installations of tile or sculpture. It is easy to make "assumptions"...... and you know what ASSumptions do. best, ...................john Link to comment Share on other sites More sharing options...
bluedawg Posted October 19, 2011 Author Report Share Posted October 19, 2011 Thank John, Makes perfect sense. Link to comment Share on other sites More sharing options...
Pres Posted October 19, 2011 Report Share Posted October 19, 2011 For Cone 6 this glaze formula is WAY oversupplied with SrO flux at 0.47 moles. Also oversupplied with the KNaO fluxes at 0.43 moles. Then you add in the fact that the percentage of copper carbonate addition is pretty high at 5% of the batch weight. The excess of the SrO and the KNaO is going to cause the glaze melt to "attack" the underlying clay body a bit, thereby pulling some of the iron out of the body into the glaze melt. So the amount of disolved metallic coloring oxides is getting on the high side in the melt. Where there is some thickness to the glaze melt, likely the thermal mass of the glaze is keeping it a tiny bit hotter during the cooling cycle than the thinner parts and it is more isolated near the surface of the glaze from any extra alumina picked up from the "attacked" clay body. This is likely retarding the cooling a bit, nor is providing an inhibitor to re-crystalization, and is allowing the heavy saturation of metals (mainly copper oxide) to percipitate out on the surface of the cooling glaze. Hence the black semi-matte surface where thick. The combination of the imbalance of the fluxing oxides and the high percentage of copper says to me to keep this one off of the "working surfaces" of functional ware. Working in its favor to make the glass stronger is the high alumina number and the reasonable silica number. But still rather questionable. 50.00 Lithium Carbonate 1000.00 Strontium Carbonate 3000.00 Nepheline Syenite 500.00 OM #4 Ball Clay 450.00 Flint 250.00 *Titanium Dioxide 250.00 *copper 0.04* CaO 0.05* Li2O 0.01* MgO 0.10* K2O 0.33* Na2O 0.47* SrO 0.01 TiO2 0.57 Al2O3 2.89 SiO2 Take that fired glaze, particularly where black, and place a sample of it into a glass cup that is 1/2 full of vinegar. Place the sample into the glass so that the vinegar covers only about 1/2 of the fired sample. Let it sit there for a few days, replenishing the vinegar as it evaporates. DON'T change the level in the glass! You want that demarkation line where it is in the vinegar and where it is not to remain absolutely constant. Take the test piece out, throw out the vinegar, wash the sample with water, and then dry it off very well. Maybe let it sit for half a day so that the surface is really, really dry. Take a magnifying glass or a loupe and look at the surface where it was immersed in the vinegar and the part that was not. See if you can see surface reflectivity or color changes in the two parts. I'd be surprised if you did not. best, ...................john Good analysis john, I don't have the patience to go through such a thorough breakdown, unless I am doing it for myself. Your point about the clay metals is important and something oft over looked. I am glad there is someone here to remind of us the reaction of glaze and clay in the totality of a ceramic piece. Link to comment Share on other sites More sharing options...
lynny Posted October 20, 2011 Report Share Posted October 20, 2011 Hi all I read here every day from Australia and am constantly grateful of the sharing of knowledge and support given to other potters. But this post blew me away! How envious I am of such 'senior' knowledge in the world of clay. As someone who started this journey in my 50's after retirement I have heaps to learn, but am getting there. Wow John your head contains amazing info! Thanks for these discussions Link to comment Share on other sites More sharing options...
bluedawg Posted October 20, 2011 Author Report Share Posted October 20, 2011 I agree Lynny! Link to comment Share on other sites More sharing options...
Benhim Posted October 20, 2011 Report Share Posted October 20, 2011 I didn't see this mentioned in any of the posts maybe I just missed it, but Lithium does decay in a wet glaze. Any lithium recipe needs to be mixed and used immediately. If let set in the studio for more than just a day or two it will begin to change drastically. Link to comment Share on other sites More sharing options...
bluedawg Posted October 20, 2011 Author Report Share Posted October 20, 2011 I didn't see this mentioned in any of the posts maybe I just missed it, but Lithium does decay in a wet glaze. Any lithium recipe needs to be mixed and used immediately. If let set in the studio for more than just a day or two it will begin to change drastically. More good info. Thanks Benhim! Link to comment Share on other sites More sharing options...
EarthnElements Posted October 24, 2011 Report Share Posted October 24, 2011 I am a beginner and trying to mix a nice variagated turquoise cone 6 glaze. I have tried two different recipes and they both came out gunmetal black. After the first one I thought for sure I did something wrong but now I am wondering if maybe it's something else. My materials are very old... is there a shelf life to carbs and oxides? I attaching a photo of the glaze. You can see it on the top portion of the vase. It kind of breaks green at the edges but you can see where the gunmetal black has pretty much taken over... This is the second recipe I tried (I no longer have the first) : 3) Weathered Bronze Green - Cone 5-6 Lithium Carbonate 50 Strontium Carbonate 1000 Neph Sye 3000 Ball Clay 500 Flint 450 Also add: Copper Carbonate 250 Titanium Oxide 250 I use Weathered Bronze Green on many items - it is not a food safe glaze - don't use on functional wares. (Most any matte turquoise should not be considered food safe unless tested in a lab for leaching) It needs to be thick in order to get the green, where thin it will be black. I mix it so that it is as thick as split pea soup, seriously. ) WEATHERED COPPER BRONZE GREEN 60 Neph 20 Strontium 10 Ball Clay 9 Flint 5 Copper 1 Lithium 5 Titanium add Cmc for brushing I can point you in the direction of some of my items that have been glazed with it if you like, I tend to use it most frequently layered over a few other glazes to vary the tone of the green. Also reducing the amount of copper carb will lean you more towards turquoise. PS - your copper carb or any "old" oxides are fine unless they have become contaminated with some foreign materials, there is no shelf life so to speak. you can see some in my etsy shop for examples www.earthnelements.com Link to comment Share on other sites More sharing options...
bluedawg Posted October 24, 2011 Author Report Share Posted October 24, 2011 Nice thanks! I looked at your shop, Really nicely done. I will try this. Just a question or two...what is the number before the item and I see you have copper listed twice is that a typo or on purpose. Also is this oxidation or reduction? Are you firing to cone 6? Thanks! Link to comment Share on other sites More sharing options...
bluedawg Posted October 24, 2011 Author Report Share Posted October 24, 2011 Oh wait - duh I get it the second number is just half recipe Link to comment Share on other sites More sharing options...
EarthnElements Posted October 24, 2011 Report Share Posted October 24, 2011 Nice thanks! I looked at your shop, Really nicely done. I will try this. Just a question or two...what is the number before the item and I see you have copper listed twice is that a typo or on purpose. Also is this oxidation or reduction? Are you firing to cone 6? Thanks! Yes a typo I just corrected. Sorry about that Also I had the 1/2 batch amounts noted to the right of the chemicals, forgot to delete that out before posting. I have a couple of other nice turquoise glazes in matte finishes very similar if you are interested in trying. Cone 6 oxidation Link to comment Share on other sites More sharing options...
bluedawg Posted October 24, 2011 Author Report Share Posted October 24, 2011 Yes, Please. I would love to try them. Link to comment Share on other sites More sharing options...
JLowes Posted October 24, 2011 Report Share Posted October 24, 2011 Bluedawg, The glaze in the picture was fired electric oxidation to Cone 6. It is a Pete Pinnell glaze developed for Cone 9, but it does "look" nice at Cone 6. Like the others said, not for inside food containing vessels. Check out the link to John Hesselberth's site Frog Pond Pottery for a data sheet posted on the glaze: http://www.frogpondp.../glaze0022.html John L. Link to comment Share on other sites More sharing options...
EarthnElements Posted October 25, 2011 Report Share Posted October 25, 2011 Yes, Please. I would love to try them. Here is one of my favorites - best on light body/white clays. Not food safe, use a different glaze for a liner. MY TURQUOISE MATTE 15 Strontium Carb 60 Custar Feldspar 20 Dolomite 5 EPK 3 Copper Carb 1 Bentonite Link to comment Share on other sites More sharing options...
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