tag:blogger.com,1999:blog-3580639918656230427.post7316981437304758812..comments2024-03-22T17:41:17.625+13:00Comments on Peter's Pottery: Cone 6 glazes, bowls, tiles, and tomato sex!!Peterhttp://www.blogger.com/profile/03078608554226394069noreply@blogger.comBlogger74125tag:blogger.com,1999:blog-3580639918656230427.post-61699970236063108102023-06-30T15:45:33.442+12:002023-06-30T15:45:33.442+12:00Hi Samy,
Thank you for getting in touch. Welcome t...Hi Samy,<br />Thank you for getting in touch. Welcome to the world of making and glazing pots! Potting is a wonderful thing to be doing as there is always something to learn, in fact more than a life time full of things to investigate! A very wise older potter said to me when I was right at the start of learning about glazes, that it was best to begin with a clear glaze, a matte glaze, and maybe one other, and to really get to know what they can do. Those simple glazes can be made different colours by adding metal oxides to them, or glaze stains, and the clear could be made opaque by adding zirconium or tin oxide, or maybe some titanium dioxide. <br /><br />I mostly ignored that good advise and tested lots and lots of glazes, and spent many hours making things that didn't always do what I really wanted.<br /><br />One thing that it would be good to decide very early on is what temperature you will fire to. If you are firing your work at a local pottery club, then they may well require that their kilns only be fired to Cone 6 (about 1220 C or 2228 F) so if that is the case, then the clay that you make pots from should also be a stoneware clay that will mature at that temperature (a cone 10 stoneware would be under fired at Cone 6). <br /><br />The post that you have left your comment on is about cone 6 glaze, and I would recommend trying the simple glaze recipe that you will find with this post, the one that has equal amounts of 5 ingredients, (Feldspar, China Clay, Quartz, Wollastonite, and a borax frit). You can add some colour to this base recipe with any of the common metal oxides that are used in potting, copper, iron, manganese, cobalt. Have a good look at the photos that are with my blog post, there are lots of test tiles and most are the same glaze base with different metal oxides or glaze stains colouring them.<br /><br />You might also visit digitalfire.com for a whole library of information about glazes. A glaze forum where people upload recipes and photos of glazes is glazy.org this is a really good place to search for recipes of glazes that suit what ever temperature you may wish to fire to.<br /><br />As to 1000s of questions, it is best just to make a start with a simple glaze recipe and see what you can learn from that. <br /><br />Let me know how you get on,<br /><br />Peter<br /><br />Peterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-43197558179906889432023-06-30T10:13:44.651+12:002023-06-30T10:13:44.651+12:00Hello Peter,
I am new to the pottery world. I have...Hello Peter,<br />I am new to the pottery world. I have recently started learning about glazes.. I have 100's of 1000's of questions and glazes i want to try out, can you help me with some questions? Let me know where i can connect with you maybe insta or email. It would help me a lot to learn from your experience as i am a noob in this field and eagerly trying to learn everyday.Samy21https://www.blogger.com/profile/11176431119402641336noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-91973538947140512592018-07-10T01:07:46.981+12:002018-07-10T01:07:46.981+12:00Hello Peter; You do very beautiful work. I really ...Hello Peter; You do very beautiful work. I really like the Chrome tin Red. I Thank you for being so generous with your findings. Thanks for sharing. I can’t wait to try them out. I am new to the world of pottery. I’ve only been doing it for a few yr’s. It can be a little overwhelming if you look at the big picture and all that there is to know. It might scare someone away. ha I love working with clay and now am starting to experiment a little. Its fun become more confident in this field. I know there is still tones I need to learn, but I’m excited about the possibilities. Web pages like yours keeps fanning the flame and giving me direction. I still have that beacon in my mind telling me to move cautiously where experiment with glazes is concerned. I still have some attachment to my pieces. Most times I find opening the kiln the most exciting thing. Its is always surprising and exciting seeing what your glazes have done. Thanks again for your site I’m so glad I found it. May waves of positive energy fill your sails.BackYard Potterhttps://www.blogger.com/profile/14712115191880649680noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-67179554300887368962018-04-06T14:58:21.702+12:002018-04-06T14:58:21.702+12:00Hi Patrick,
How sad that the tiles didn't turn...Hi Patrick,<br />How sad that the tiles didn't turn red, that is very strange and frustrating. The thought about Tin oxide was interesting, and it certainly would be a good idea to try some from a different source, just in case the one you are using is not all it claims to be! <br /><br />Best Wishes,<br /><br />PeterPeterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-86773153626777439702018-04-06T14:28:53.060+12:002018-04-06T14:28:53.060+12:00Hi Peter,
The last test tiles also didn't ...Hi Peter,<br /><br /> The last test tiles also didn't turn red. I have now confirmed that if the glaze is on too thin then it stays white/grey. I'm running another round of test but this time I'm doing 3 and 4 coats. I'm going to have these tiles sitting on a pot lifter so it doesn't stick to the kiln shelf in case it runs. I'm also putting it on a glossy black glaze as the 2nd layer just to see how it interacts with other glazes.<br /><br /> The Kaolin (Tile #6) didn't produce much of a different result than the EPK one. So I can rule that out. I found out the origin of my ball clay and it turns out to be Kentucky OM#4 Ball Clay which is very popular and prevalent in many recipes. What I noticed though is that when OM4 is used in a recipe, it's usually in conjunction with a Frit 3134. Usually it 14% Frit 3134 and 18% OM4 Ball clay.<br /><br /> I'm wondering whether my Tin Oxide is low quality or something. We bought it from somebody else that was closing their pottery studio and I have no idea how good it is. I'm getting a different Tin Oxide from a reputable vendor so that I know that I can trust the chemical. I bought Chrome Oxide from an actual pottery supply place so I know it's good. It's just so weird that getting red can be this hard when I read in many books that Tin Chrome red is quite easy to produce. It's interesting because it seems as if the Tin didn't react with the chrome much at all.<br /><br /> I also made a Floating Blue glaze which is quite popular and the recipe is consistent. That one actually turn out OK on the test tiles. I'm running one more test over a glossy black glaze to see how it looks. I'll do another run with a small bowl and then do a leaching test to check for food safety. Once that's done, I'm going to scale it up to a 5 gallon bucket. It'll be my first made-from-scratch glaze! Once I got more reliable food safe working glaze, we can cut down on the commercial glaze we buy and that should save us a lot of money! <br /><br /> Thank you so much for getting me hooked on making glaze. Your blog is what really inspired me.<br /><br />Anonymoushttps://www.blogger.com/profile/16288888023463494196noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-87224236652916466652018-04-01T21:14:56.568+12:002018-04-01T21:14:56.568+12:00Hi Patrick,
Well done! I wish I could employ you t...Hi Patrick,<br />Well done! I wish I could employ you to make up my glazes for me you are doing a great job. You are right in your calculations, although I must say that x 5 seems one less step than x 10/2! You put more effort into glaze preparation than I do. I don't do much of a dry mix, just a light stir, careful not to create dust. I put a measured amount of water into a mixing bowl and add the dry ingredients to water, and generally just let it sit for a while without stirring. I usually don't have the time to leave glazes for hours, but ideally leave a glaze to sit over lunchtime. When I resume work I then stir things up before sieving. A paint stirring attachment for an electric drill is a great invention and works really well for larger quantities, or I sometimes use a small kitchen blender for small amounts. If I make 2 liters or so of glaze I often put a bucket of glaze on my electric potter's wheel and get the wheel to spin the container of glaze whilst I hold a stirring paddle steady! Works well and isn't as noisy as a drill so I can listen to the radio whilst the wheel does the work!<br /><br />The brown clay is probably not the ideal body for this, but I would have thought that the magic should still happen and red appear!<br /><br />Best of luck with the new test tiles, I do hope something works!<br /><br />Peter<br /><br /><br />Peterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-61564596431244720312018-04-01T13:45:09.810+12:002018-04-01T13:45:09.810+12:00Hi Peter,
I calculated the recipe out by weigh...Hi Peter,<br /><br /> I calculated the recipe out by weight before I started mixing the dry chemical together. I started the calculation out at 1000 g so I could just easily multiply the recipe you have just by 10 since your recipe is for 100 g. I then divide everything by 2 to get to my 500 g batch. The 500 g doesn't count the additives (Tin and chromium). I just did the same thing with them (multiply 10 then divide by 2). I guess I can alternatively just multiply everything by 5. My latest batch I just made 100 g as you suggested in the last post. I learned quickly that 500 g is a bit much to waste when the glaze doesn't work. In any case, here's my 500 g batch:<br /><br />Gillespie Borate 105g<br />Neph Syenite 80g<br />EPK 55g<br />Whiting 100g<br />Silica 160 g<br />Tin Oxide 25 g<br />Chromium Oxide 0.75g<br /><br />If I take 0.75g / 500 g, I get 0.0015 or 0.15% for Chromium Oxide. So I think the math is correct for the weight of the ingredients.<br /><br />I mixed the dry chemical together first and then slowly added water until I get to about 450 g of water weight in. I measured out the water ahead of time to get about 45:50 ration water:dry ingredients. I guess I'm treating like how I mix stuff when I do baking. I was reading in some books that it's better to have a bucket of water and add dry chemical to it so that the powder has time to settle in the water. I actually didn't wait overnight to mix the wet and dry glaze together as I discovered later suggested in this book. I just started mixing the ingredients with my electric drill and a mixing head. I ran the mixture through a 100 mesh sieve twice. I wasn't sure if I have lost too much stuff from the mixture since I notice that not all the dry stuff got through. Do you normally wait a day to mix the glaze and then run it through the sieve? I just purchased an 80 mesh sieve since the book suggested using an 80 mesh.<br /><br /> After everything went through the sieve twice, I measured the specific gravity by putting the glaze in a cup and then divide that weight by water weight of the same volume. I ended up with 1.7 at first and I added more water to get to 1.53. I just picked that because I was mixing a commercial dry glaze just before doing my own. That particular glaze called for a 1.53 specific gravity, but it was a black Temoku glaze so maybe it needed to be thicker. The other commercial glaze I use have varying suggested specific gravity from 1.3 to 1.65 so I just used that as the ball park value.<br /><br /> One thing I didn't mention last time was that my test tiles were bisque brown clay rather than white clay. I wonder whether that could contribute to the problem. I should try making test tiles from white clay as well. Both brown and white clay types were for cone 6 vitrification so that the glaze doesn't craze on the clay body (which it didn't). The fired glaze texture was smooth and shiny with no bubbles, cracks, or crazing. It's just the streak of red and mostly white/light grey being the result.<br /><br /> I'm anxious to see the result of the new test tiles since I mixed the glaze up very thoroughly and diluted it down to sp.g = 1.45 as I mentioned in the last post. The glaze did apply thinner so I'm curious to find out whether it works better. I also mixed up another batch but using Kaolin Georgia Tile #6 instead of EPK. This batch I also mix all the main ingredients first thoroughly and then added Tin Oxide and mixed thoroughly and then finally added Chrome oxide. I just tried to make sure that I really get everything mixed together. I didn't wait 24 hours but I did wait 30 minutes before running the glaze through the same 100 mesh sieve. I only did it once this time since I only had a 100 g batch and it went through the sieve pretty easily with almost not clumps left over on the sieve.<br /><br /> I'm crossing my finger and hoping that either of the batch would work this time. I'll let you know once the tiles come out.<br /><br />Thanks,<br />PatrickAnonymoushttps://www.blogger.com/profile/16288888023463494196noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-30074555983279389282018-04-01T11:05:30.807+12:002018-04-01T11:05:30.807+12:00Hi Patrick,
Sorry you didn't get the red, but ...Hi Patrick,<br />Sorry you didn't get the red, but I am glad there were some spots of red there... that is a start!<br /><br />I don't think that the specific gravity will make much difference with this. My own experience of this glaze is that it is red unless very thin, such as over rims of cups, when there is sometimes a "break" to white with just a hint of very pale green. Where very thick I get a more purple version of the red.<br /><br />I rechecked the recipe, and the amounts of everything are correct (I had wondered if I had made a typo like getting the decimal point in the wrong place for the Chromium Oxide!) <br /><br />It is interesting that your glaze has red in some spots, but not in others, and that it is worse when the glaze is thicker. I realize that you have probably done this very well, so please forgive me for asking this, .... did you sieve the glaze through at least an 80 mesh sieve? I would do this 2 or 3 times. (It might be worth trying 100 mesh). It sounds from your description like the chromium may be unevenly distributed in the glaze batch.<br /><br />Another cause for this would be if your weighing of 0.15 was out for some reason and the amount you put in was a lot less, 0.015?? (I have been known to make a power of 10 error in an oxide in the past with one glaze that I made up, on that occasion I added 10 times too much cobalt... Decimal points are frightening things, and such an error is horribly easy to do!).<br /><br />My other thought is that, if you have any of your glaze batch left over, you could try adding an extra bit more chromium oxide (add only a tiny bit), and sieve really well to disperse it. <br /><br />The Gerstley vs Gillespie is interesting. I think you should definitely try the Gerstley Borate, as I know that the chemistry of it and its various substitutes can vary quite a bit.<br /><br />Your EPK should be OK and no need to substitute for another Kaolin.<br /><br /><br />Good luck with the testing. Sorry this is being difficult, but I am glaze you are quite enjoying it. I will think of you when I am next stirring glazes. <br /><br />Best Wishes,<br /><br />Peter<br />Peterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-52392157018527261602018-03-29T11:43:05.433+13:002018-03-29T11:43:05.433+13:00Hi Peter,
The book is excellent. It's really...Hi Peter,<br /><br /> The book is excellent. It's really is a potter's dictionary explaining so much essential information.<br /><br /> The test tile came out after my recipe as followed:<br /><br />21 Gillespie Borate<br />16 Nepheline Syenite<br />11 EPK<br />20 Whiting<br />32 Silica<br /><br />Add: 5 Tin Oxide<br />Add: 0.15 Chromium Oxide<br /><br />The tile came out white with some red in some spot. Looks almost like a red peppermint candy cane with more white than red. Or maybe like a tub of yogurt with some red strawberry sauce. When using 2 coats, it's definitely more white with little red streaks compared to one coat. I don't know whether the glaze was too thick. I measured it to be at 1.53 specific gravity. Maybe this should be more liquid? I'm going to try to mix it down to 1.3 specific gravity so it's a bit thinner and see what happen. Using EPK makes it not runny like Ball Clay did so that's good, but I was a little disappointed that it's not entirely red. Do you happen to know what your specific gravity was for your recipe?<br /><br /> I also did some leaching tests on my accident green glaze using the lemon and vinegar leaching method. The leaching didn't happen so the glaze is pretty safe. I didn't keep the glaze though since it was way too runny. I'll do the test on this red one after I figure out how to get it to be more red than white.<br /><br /> I might try a new batch using Gerstley Borate instead of Gillespie Borate to see whether that would make a difference. We just got some Laguna Gerstley Borate to try. I also just got some Georgia Kaolin to try instead of EPK but maybe that's another experiment.<br /><br /> This is quite fun actually. I'm going to try to make 100 g batch like you suggested so that I can make several combinations to try out. Maybe one will finally work.<br /><br />Thanks,<br />PatrickAnonymoushttps://www.blogger.com/profile/16288888023463494196noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-79604266776541149462018-03-25T22:27:37.579+13:002018-03-25T22:27:37.579+13:00Hi Patrick,
Good to hear from you. I'm just he...Hi Patrick,<br />Good to hear from you. I'm just heading off to bed, but thought I'd check the emails and so on before I did, and found your comment there. Glad you are trying the glaze again. EPK should work well I think. I was a bit perplexed by the green glaze being extremely runny and it makes me a bit suspicious about the Ball clay that you used, have you made other glazes with it? The glaze has never been particularly runny, and I am surprised that the switch from china clay to ball clay would make so much of a difference. I might try that myself sometime and see if I get a similar result.<br /> <br />I find that I can make quite small amounts of glaze for testing these days, now that I have electronic scales and can measure accurately! If the glaze is a simple one, I might just make 100 g of dry ingredients, but if the glaze has very small amounts of an oxide, as in the case of this one, I will often make 200 g of the dry ingredients up instead of 100 g. <br /><br />These days I also always weigh the water that I add. As a "rule of thumb" most glazes need roughly an equal weight of water to the dry ingredients.... in other words, 1kg of materials = 1kg of water (which is 1 ltr). I would usually start by adding 900 g of water to 1000 g of dry ingredients then top it up with additional water once I have sieved the glaze and have got more idea of how thick or thin the glaze is. <br /><br />Very pleased you have ordered the book, it is one that you should find useful for many years. <br /><br />Any help I can be is my pleasure :-)<br /><br />Peterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-86679595557109181842018-03-25T14:28:15.630+13:002018-03-25T14:28:15.630+13:00Peter,
Wow, I love the line measurement techni...Peter,<br /><br /> Wow, I love the line measurement technique you have. Very clever! I didn't even think about how I can measure 10 grams easily with the scale and all I had to do was divide it into 10 units to get 1 gram precisely! I did get a very precise electronic gram scale and just measured out 0.75 g today to make a new batch. I decided to cut the batch size in half so I don't waste the ingredients if this recipe didn't work out.<br /><br /> I decided to not keep the green glaze since it was extremely runny and the test tiles were stuck to the kiln. My suspicion was that the Ball Clay of unknown origin might have contain too little silica and alumina compared to China Clay. We bought Ball Clay from a bankrupt studio for cheap but it didn't have any information on it other than "Ball Clay" on the 5-gallon bucket. So my new batch of Chrome Tin Red uses Edgar Plastic Kaolin (EPK) instead of Ball Clay that I have. I was reading about how to fix running glaze and many people suggested adding more Silica or Alumina. I didn't try changing Silica percent since Ball clay is already high in Silica so maybe what I need more of is the Alumina, I figure try using EPK first since it's higher in Alumina content than Ball Clay. EPK = 37% Alumina, 46% Silica. Ball Clay = 25% Alumina, 59% Silica (according to DigitalFire.com). I also think EPK is closer to China Clay content (Alumina: 36.3% Silica: 47.8%)<br /><br /> I'm crossing my finger to see how this new batch turns out. We are doing a Cone 6 firing tomorrow. I'm more cautious with the test tile this time and have a catching bowl underneath in case it runs again. I'll let you know how it comes out.<br /><br /> Thank you for the book suggestion. I have ordered it and it's going to be a great read. I also want to thank you for all your guidance. It's quite amazing that I have gotten to talk to a very experienced and responsive potter at the other side of the world.Anonymoushttps://www.blogger.com/profile/16288888023463494196noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-6482079609863720472018-03-21T18:43:02.453+13:002018-03-21T18:43:02.453+13:00Hi Patrick,
Hey... you've just invented a gree...Hi Patrick,<br />Hey... you've just invented a green glaze! :-) <br /><br />I suspect that 0.8 would be too much for the red.. so more accurate measuring is essential. One trick I used in the bad old days before I finally gave in and bought some nice accurate electric scales, was to weigh out 10 grams of chromium oxide and carefully make a line of it on a clean piece of paper. The line would be about 1 cm wide, a couple of millimeters thick and as long as 10 grams needed. I would then carefully divide this line into 10 with a knife, so that each piece now weighed a gram. Then I would cut a one gram piece in half, giving me 2 half gram pieces, and half again, giving me 0.25 pieces. It was possible to be accurate enough to get chrome reds reasonably well that way although good electric scales make things so much easier!<br /><br />I often have used Gillespie borate instead of Gerstley, and that has worked well.<br /><br />Regards "quarantine", 0.8% is still a very low amount of chrome oxide in the glaze and my own feeling is that it would be very safe and unlikely to do harm to anyone. <br /><br />Regards "a lot of learning to do", one of the really great things about making pots is that the learning never needs to stop! This means that going into the studio to make pots can be a daily adventure, rather than a boring chore. One of my favorite books is "The Potter's Dictionary of Materials and Techniques" by Frank Hamer. I suspect that it would be available through Amazon or other book sellers. The Potter's Dictionary is nicely written and makes wonderful "bedtime" reading! <br /><br />Good luck with the Chrome/Tin glaze, I'm sure you'll start to get results when you measure more accurately.<br /><br />PeterPeterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-49625887339540361832018-03-21T16:34:18.658+13:002018-03-21T16:34:18.658+13:00Hi Peter,
We just did a cone 6 fire of the Tin/ch...Hi Peter, <br />We just did a cone 6 fire of the Tin/chrome glaze tonight and the result came out somewhat disappointing. It was green!!!<br /><br />I think I added too much Chrome Oxide. My scale was not able to get a sub decimal places for grams. I was making a small match using a the recipe to get to about 1000 mg dry weight. With the recipe, I need 1.5 grams of Chrome Oxide and 50 grams of tin oxide. I think the tin oxide was correct, but I think chrome oxide was probably close to 8 grams by mistake (0.8% instead of 0.15%). I also accidentally substituted China Clay with Ball Clay. I also found that we used Gillespie borate instead of Gertley Borate because that's all we had and it was supposed to be a 1:1 substitute.<br /><br />I think the Gillespie Borate and Ball Clay substitutes might have been ok, but the too high percentage of Chromium Oxide is what turned the glaze green instead of red/purple I was expecting. Do you think that's a correct assumption?<br /><br />I'll mix up another batch but this time I'll get a more precise measurement of the chrome oxide with my new scale that has a 0.01 gram precision.<br /><br />I only glazed my test tile and a couple of small bowls with this glaze. Should I quarantine them since the chrome oxide level is a bit too high. Not sure how safe it is being at 0.8% instead of 0.15% of chrome oxide. What's the rule of thumb in terms of percentage vs. toxicity for chrome oxide? I know that copper carbonate and cobalt carbonate should be under 2%. I'll have to try a leaching test to see.<br /><br />You make glazing look easy, Peter. I do have a lot of learning to do.<br />Thanks,<br />PatrickAnonymoushttps://www.blogger.com/profile/16288888023463494196noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-72664307463277063112018-03-14T11:15:11.545+13:002018-03-14T11:15:11.545+13:00Hello Patrick,
Fear not! The clay content of this ...Hello Patrick,<br />Fear not! The clay content of this glaze is not all that high, at 11 percent, so the "contamination" by trace elements from ball clay will probably not be very significant if it is a white ball clay, so I would not be surprised if the colour was unaffected. Definitely give it a try. We occasionally used to be able to get a local ball clay here that was very rich in iron oxide, and was an earthy yellow colour, and something like that may have been a problem, but the usual commercial varieties seem fairly low on iron oxide. It is possible that the glaze will mature at a very slightly lower temperature than if it were made with China Clay, but this should not be a problem as I know from my own experiments that this glaze will cope with being fired to above cone 7 and a little below cone 6.<br /><br />Regards China Clay, I use what ever China Clay I have on hand at the time, and don't make any attempt to use a really pure one such as Grolleg. Grolleg Kaolin would be useful if I was making a blue celadon for reduction firing, or making a porcelain body, but most of the time is not really needed. <br /><br />Ball clay shrinks more than china clay as it dries, so you may find that you have minor shrinkage cracks in the freshly applied glaze. The modest amount of clay in this glaze should mean that this isn't really a problem. You could lightly smooth over any cracks in the dry glaze with your finger, but these will very likely heal when fired.<br /><br />Good Luck!Peterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-72874169078525612212018-03-13T15:05:44.549+13:002018-03-13T15:05:44.549+13:00Hi Peter,
Looks like I messed up the recipe fo...Hi Peter,<br /><br /> Looks like I messed up the recipe for my first batch I made this weekend. I have not tried firing the glaze on my test tile yet to see what would happen, but I will. I accidentally substituted China Clay with Ball Clay. Please correct me if my information is wrong. Technically Ball Clay is a Kaolinite mixture and it's a secondary clay so it's not as pure like China Clay (Grolleg Kaolin). Bally Clay is also more plastic than pure Kaolin. I didn't have Grolleg on hand but I'm getting some soon so I'll mix up a correct batch to test also. <br /><br /> Do you have any ideas of what the result might be with Ball Clay substitution in place of China Clay? I imagine it's going to be a lot duller in color since Ball Clay is not as pure and white. The contamination of various minerals in Ball Clay would probably affect the end result as well. I looked up the chemical make-ups of Ball Clay and it seems similar to Grolleg Kaolin but it has about 10% lower content of Al2O3 but 10% higher content of SiO2. The other chemical (CaO, MgO, K2O, Na2O, TiO2, Fe2O3) are similar. Shrinkage (LOI) is also about the same at 12%. <br /><br /> I guess I'll just try it anyway and see since I have seen Ball Clay and China Clay in the same recipe for other glazes but usually a lot higher percentage of China Clay compared to Ball Clay. Hopefully the glaze won't be crazing since having a high plasticity clay might make it not stable.Anonymoushttps://www.blogger.com/profile/16288888023463494196noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-51639775856240903812018-03-09T22:13:49.813+13:002018-03-09T22:13:49.813+13:00Hi Patrick,
I'm impressed by your care with gl...Hi Patrick,<br />I'm impressed by your care with glaze preparation, you sound like you are doing a great job.<br /><br />I think that it would be good practice for the children to wear gloves when glazing, particularly young children. The hazard whilst actually glazing is probably quite minimal, but the real difficulty with children (and adults!!) is to make sure that the hands are well washed afterward and there isn't glaze trapped under fingernails and so on. If gloves were worn when glazing, and taken off afterwards, it would reduce the risk of a child walking away with glaze on the hands and sucking a thumb, or eating lolly or lunch! <br /><br />Do let me know how the chrome/tin glaze works out for you. I find it really helpful to make sure that chrome/tin reds are sieved through at least an 80 mesh sieve 2 or 3 times to make certain that the chrome is well dispersed through the glaze. 0.15 is a tiny amount, but should work well. If you wanted to you could experiment with a little more chrome oxide, but 0.5 is probably the absolute maximum. Additions of very small amounts of cobalt carbonate can shift these glazes from red through a useful range of purples to blue.<br /><br />Best Wishes,<br />Peter Peterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-73515190602938519962018-03-09T18:20:47.248+13:002018-03-09T18:20:47.248+13:00Thank you so much, Peter. I do feel much better a...Thank you so much, Peter. I do feel much better after reading your comments. I'll be the only one handling the chormium oxide in the studio as far as dry ingredients go. We actually have a separate area where I do all the mixing outside near the dry chemical storage with a fine particle filter dust mask and safety goggles. I also always wear rubber gloves when working with any of the ingredients. Are there some potential hazard for kids to use the liquid glaze if they want to do the dipping method? The 0.15% of Chromium oxide along with other ingredients mixed with water should be quite diluted I imagine. Maybe I should still have them wear gloves when using this glaze. Perhaps I should just make that a practice for any children using the glaze anyway so that they never have to get their skin in contact with the chemical. OK, I'm excited to see how this Red Tim Chrome glaze comes out. Thanks again.Anonymoushttps://www.blogger.com/profile/16288888023463494196noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-78308033405861886352018-03-09T16:18:03.340+13:002018-03-09T16:18:03.340+13:00Hello Patrick,
Good to hear from you. The question...Hello Patrick,<br />Good to hear from you. The question of toxicity of glaze materials is an important one, especially if you are dealing with children in your pottery programme. Without being paranoid, I still treat most glaze materials as if they were potentially hazardous. One of the most insidious hazards in a clay workshop is actually the dust from dry clay itself, and aprons and work areas should be kept clean and spills mopped up. Regarding Chromium Oxide, as a raw material I would not let young children work with it. Some Teenagers, maybe, but only if sensible and under supervision, and with disposable dust masks. <br /><br />Chromium oxide as part of a fired glaze. I am confident that, if this particular glaze is fired correctly, the tiny chromium oxide content will present no hazard. I also would be confident that, at cone 6, this glaze is unlikely to contaminate other work in the kiln, or the kiln itself. <br /><br />Regarding testing, I have not sent a sample of this glaze to a lab for testing. <br /><br />As a "rule of thumb" I like to keep any hazardous metal oxides at below 2 percent in any glaze that I make that might be used on domestic ware. I would normally use a safe "liner" glaze inside a mug,cup, teapot or food container. A simple and reliable tenmoku glaze is what I often use for that, and if any metal was released from the glaze, it could only be iron oxide... which might even be of benefit if it were ingested!<br /><br />I know that many potters, including those running children's classes, use glaze stains. And some manufacturers advertise them as being "safe". I still would treat such things with caution, and the "safe" claim with skepticism! I would try to keep to a relatively low percentage of them as colouring in a glaze to make quite sure that they were well incorporated into the glaze matrix.<br /><br />Hope this of is of some help. <br />Peter<br /><br />Peterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-83301858716465860802018-03-09T14:30:43.360+13:002018-03-09T14:30:43.360+13:00Additionally, have you sent out a piece of the Chr...Additionally, have you sent out a piece of the Chrome-Tin red to a test lab for leaching and toxicity test at places like BSC lab? <br />http://www.bsclab.com/Pottery_Testing.html<br /><br />I'm thinking about sending it out for an analysis so that I can feel safe enough to use it in our studio. <br /><br />Thanks,<br />PatrickAnonymoushttps://www.blogger.com/profile/16288888023463494196noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-75821407698526788532018-03-09T14:26:54.006+13:002018-03-09T14:26:54.006+13:00Hello Peter, this is a wonderful blog article. I&...Hello Peter, this is a wonderful blog article. I'm quite fascinated by the chrome-tin red glaze and I'm planning to make a batch to try myself using your suggested recipe (or June Perry's). One question I have is the toxicity of the chrome oxide. I think you addressed some of this in your reply to somebody else, but I wondering about the firing of the glaze. In Brian Taylor and Kate Doody's GLAZE book, they mentioned that chrome oxide fume is very toxic. Is it a good idea to use this glaze and fire it in a kiln that mainly used for firing non-toxic and food safe glazes? I'm worried about chrome oxide residue and how it would contaminate the entire kiln when we fire it. I'm using the 0.15% as suggested in the recipe so that's not a lot of it in the entire glaze content. Nevertheless, based on your experience, is it safe enough to fire at Cone 6? We work with a lot of young kids in our pottery program (age 4-12) so safety is our utmost concern. Your insight would be greatly appreciated.<br /><br />Thanks,<br />PatrickAnonymoushttps://www.blogger.com/profile/16288888023463494196noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-80544591747225450562016-09-22T21:12:09.194+12:002016-09-22T21:12:09.194+12:00Hi Pete the Potter,
Good to hear from you. I did a...Hi Pete the Potter,<br />Good to hear from you. I did a Google search for Celestial Blue and could not find a recipe, but did see a commercial glaze of that name that was very fluid and had small crystals that had formed in it. I haven't got a recipe for Celestial blue, but it is possible to make a very dark transparent blue just by adding about 2 percent cobalt oxide to a clear glaze base to a cone 6 base glaze such as this one.<br /><br />20 Wollastonite<br />20 Fritt 3134 (F 4108)<br />20 Potash Feldspar<br />20 Silica<br />20 China Clay<br /><br />This would give you something dark, transparent, and blue, but it may be that there are other qualities that you are seeking, such as a glaze that flows or runs, or a glaze that "breaks" to another colour where thin. You could make this glaze a little more fluid by substituting ball clay for china clay and Soda Feldspar for Potash Feldspar. <br /><br />Tony Hanson's wonderful digitalfire.com website has a recipe for a fluid cone 6 glaze https://digitalfire.com/4sight/recipes/cone_6_clear_fluid-melt_clear_base_125.html<br />Something like this could well be an interesting base for experimentation, (you could leave out the tin and copper and add 1 or 2 percent cobalt oxide) and his explanation of how this glaze works is well worth reading.<br /><br />Good Luck! PeterPeterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-57810065889004430402016-09-20T08:02:48.717+12:002016-09-20T08:02:48.717+12:00I am looking for a recipe for Celestial Blue, con...I am looking for a recipe for Celestial Blue, cone 6, oxidation. A deep dark transparent blue. Do you have anything. Thanks, Pete Pete the Potterhttps://www.blogger.com/profile/09288523632922414949noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-30838365294653347592016-02-19T16:02:48.082+13:002016-02-19T16:02:48.082+13:00Hi EarthWind Stoneware,
Thank you for your questio...Hi EarthWind Stoneware,<br />Thank you for your question, it is good to hear from you. I think that I used the same base glaze for most of the commissioned bowls. (I think there may have been two bowls that had other bases, one being the chrome/tin red glaze, and the other being a dark green bowl where I probably added some dolomite to the regular base.)<br /><br />The cone 6 base<br /><br />20 Wollastonite<br />20 Fritt 3134 (F 4108)<br />20 Potash Feldspar<br />20 Silica<br />20 China Clay<br /><br />is a very useful and reliable one. It will give a clear glaze at cone 6, so if you want it to make a colour such as yellow, green or blue you will need to add something to it. Really you have 2 choices, one is to add a glaze stain (and this is what many people do these days), or the other is to use metal oxides. <br /><br />Glaze stains are available in nearly every colour now and are fairly easy to use. Most will be compatible with that glaze base. In the USA I think many potters use Mason Stains, but other brands are available too, just ask your pottery materials supplier. As a rough rule of thumb, you probably will need between 5 and 10 parts by weight of glaze stain for every 100 parts by dry weight of your glaze ingredients, but you will have to test this. I find that it is helpful to have a good yellow glaze stain available for making bright yellows, I did use a turquoise blue stain for one of the bowls, and a bright green stain for one of the others. <br /><br /><br />Metal oxides have a more limited range of colour (and a potter who mostly uses oxides will probably also need one or two glaze stains to give a more complete colour range). Oxides often give a more "natural" look than stains. Most metal oxides are much "stronger" than the stains, and you will find that even 0.5 percent of cobalt carbonate with give a pale blue. Chromium oxide is also very strong and less than 1 percent in a glaze will be adequate (more than that will give a rather nasty opaque paint-like mid green). <br /><br />A useful selection would be cobalt carbonate (for blue), copper carbonate (for green), red iron oxide (for an earthy yellow, rust red, brown, or nearly black), manganese dioxide (brown, or sometimes brown/purple), chromium oxide (green, or blue-green with cobalt carbonate).<br /><br />For pastel colours, or if you want to cover a dark clay with a pale glaze, you may need to make your base glaze opaque. You can use Zirconium silicate for this, (often known as Zircon, Zircopax or zircosil). 10-12% will usually make a transparent glaze white and opaque.<br /><br />Many potters live to a good old age, however.... Most of the chemicals that are used to colour glazes are hazardous materials when they are in powder or liquid form, so use them sensibly. If using a dusty material, wear a dust mask. Clean hands well after using them, and clean up work surfaces, aprons and tools. Don't eat in the studio!!<br /><br />I hope that my answer isn't too confusing for you and gives you some where to start. <br /><br />Best Wishes,<br /><br />Peter<br />Peterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-50868174119252955922016-02-19T11:54:39.959+13:002016-02-19T11:54:39.959+13:00Thank you for the excellent post. I'm a newby ...Thank you for the excellent post. I'm a newby to glazes (I don't understand what chemicals to use to get certain colors...yet) and was wondering if the glaze on the commissioned set of bowls (beautiful btw) was made from this base glaze? What chemicals does one add to get the yellow, blue, and green shades? <br />bruceEarthWind Stonewarehttps://www.blogger.com/profile/11437086315804097642noreply@blogger.comtag:blogger.com,1999:blog-3580639918656230427.post-83097597742605177102014-04-06T13:49:29.875+12:002014-04-06T13:49:29.875+12:00Hi Stellaria,
Good to hear from you. Ha, Ha, rega...<br />Hi Stellaria,<br /><br />Good to hear from you. Ha, Ha, regarding "too much"?? I have a confession..., I have old shop scales that are great for 2 kg amounts of feldspar, but I struggle with measuring small quantities of oxides. I am probably fairly close to a gram or 2. My best guess is that I was using close to 0.5 percent of chromium oxide in that first batch. <br /><br />You can easily make a really nice range of purples by adding a little cobalt to this glaze. I sometimes make up a quantity of the base glaze, split it in half. In one half I make the regular chrome-tin red, and in the other I make up the base plus 2 percent of cobalt carbonate. This makes quite a useful strong blue. Then I make a series of mixtures between the two. That part can be done by eye. <br /><br />Also note.... Glaze thickness does play some part in how this glaze looks. If really thin, it can "break" to a really pale green, if very thick it can become more purple. I suspect that the boron in the Gerstley Borate is the cause of this. In a clear borax based glaze, there is a great tendency to get a cloudy blueish area where the glaze is too thick.<br /><br />So, to sum up, try about 0.5 percent chromium oxide, and apply the glaze fairly thickly to get a purple bloom.<br /><br />Do let us know how you get on! PPeterhttps://www.blogger.com/profile/03078608554226394069noreply@blogger.com