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Are metallic glazes similar to melted metal?

37m 20s

Are metallic glazes similar to melted metal?

The podcast discusses the longevity of ceramic equipment, noting that kilns and wheels can last 25-30 years with care, though maintenance varies. The main focus is on addressing pinholes in glazes, emphasizing that "pinholes" encompass multiple distinct flaws: blistering from iron/copper decomposition, pitting from titanium, body/application voids, and true pinholes from particle packing during glaze application. Blistering, common in oxidation firings above cone 4 with dark clay or colored glazes, is often unavoidable. True pinholes relate to glaze application density. The hosts stress identifying the specific cause to apply correct fixes, such as adjusting bisque temperature or glaze consistency. While flawed pieces may be used personally if vitrified, they are not ideal for sale, and repairing them is often less efficient than creating new work. The discussion underscores the importance of understanding material behavior to reduce frustration and improve outcomes.

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[MUSIC] This podcast is a production of the Brickyard Network. To find out more about our lineup of ceramic podcasts, visit BrickyardNetwork.org. [MUSIC] This episode is brought to you by Cornell Studio Supply, located in the gem city of Dayton, Ohio. Find all your pottery and ceramic sculpture equipment and supplies with the best customer service and world-class workshops. Join us for our upcoming Rocket Kale workshop, with Lisa Orr July 18th through the 20th, 2025. Visit CornellStudioSupply.com to sign up. Cornell Studio Supply owned and operated four potters, five potters. >> Hi, I'm Rose, and I'm from the emergency glee system. And we've got your back with our brand new ceramic materials workshop consulting. For just $100, you can get 30 minutes with our team of ceramic superheroes. And we'll help you with fixing your glaze and clay disasters, finding material substitutes, decoding ceramic weirdness. So you name it. Snack your session over at ceramicmaterialsworkshop.com. [MUSIC] >> Hello, my name is Kathy King, and welcome to the Fluxake podcast. I'm coming to you from the Harvard Ceramics program in our fair city, Austin, Massachusetts. I'm here with Rose and Matt Katz of the world-famous ceramic materials workshop. And they are ready to answer your burning questions about clay and glaze. [MUSIC] >> Well, howdy, Matt and Rose. Hey, Kathy. >> Howdy, hey, Kathy. >> You know, I think we should take the conversation that we were having before we were recording and kind of go back into it. Because we were just all talking about how long our equipment has lasted. And for both good and bad. But in a prior episode, we had somebody asking about a kiln, going to Cone 10. And I don't know if people realize that with great care, these things can last a long time. >> Yeah. >> I still have my original banding wheel and my original potter's wheel. >> Okay. >> No, but I was saying like that's 30 years old. Like that stuff is still chugging. >> I mean, the potters wheel, yes, I haven't heard like people talk about longevity and banding wheels. But I know my God, those are so expensive as students. Like it was ridiculous. >> No, but you get the cheap ones. Yeah, with no mass and without the bearings. >> Yeah. >> They can go bad. They can absolutely go bad. You get corrosion on the spindle and it doesn't have good bearings. >> Bending wheels gone bad. >> [LAUGH] >> Like, kilns is a good one. I mean, we, what we were talking about before we started recording is we still had my original kiln from high school. And I was- >> I was in a long go that was. >> Mm-hm. >> [LAUGH] >> So yeah, I was in just ceramics in high school. And my generous parents supported my bad habits because I wasn't into being reckless and dangerous. So when I was in ceramics, they got me a kiln. And it, it was still, we were still using it in the workshop. Until we built where we now live, we built this place in 2021. And we had the kiln. And so we'd moved from Southern Pound, Sivanu where we'd been living for a few years up to New England, where we are now. And when we had moved, we had sort of put kilns in storage and then we sort of built the house in the workshop and the house we're here together. And we had stored all of our stuff in the workshop and that was sort of the last thing that we've built. And then one day we go out to find that our kiln was smashed. And what had happened is that the workmen had gone in there and we were moving stuff around and they dropped it and realized it was in segments. Logging seconds. So that was the official end of that kiln. But that was that that kiln was in past episodes. That's the one we would move outside used to prepare clay and bring it back inside. Yeah. And it was only our best kiln. It had been retired down to best kiln status. But it was it still worked. And I never once replaced the elements on that kiln. I never did any maintenance on that kiln ever. Yeah. It's wild to think of it. Well, I know, you know, in the studio where because we've got 350 students using it every semester, we're constantly making repairs to the kilns. But my Scott 1027 is I got it in September of 2000 when I went to grad school. And I still use it. And the but the only thing that's original to be honest is the metal banding around the side. Everything else is replaced. It's a ship of theses of kilns. Yeah. It looks like the pig pen of kilns. It's like just a little bit discolored on the outside, but producer Ben, you get do you have a store like that? Yeah, I actually have bought only second hand kilns because I'm poor. And the second can hand kiln that I currently have is also so old that when I called Scott to ask them about it, they were like, oh, that was like the first generation we made computers on. So that was probably the same as y'all, it's like 2000 early 2000. Yeah. So 25 years old. But the thing I'm most proud of not losing over my 30 year career in ceramics is I'm my original wooden fettling knife. That I got and maybe like 1998. And that thing has been to China with me. It's been all over the world. And it's just the one thing I haven't lost. I've lost all kinds of other shit, but I just haven't lost that. I think loss is the biggest problem. I think anything that I don't have is generally from loss. Yeah, just put it down somewhere and then forgot to pick it back up. But like most of the equipment, it's held up pretty well. But you know, I have seen some things like some, some things definitely like when we've gotten newer equipment, like we've seen it not some of the quality. I don't know if it's the manufacturing of the parts, but some of it doesn't hold up that well. Here we go. Old man cats in his rocking chair on the porch back when I was like, it is sweet. New things are all bad. Is all that I've said everything new is bad. Well, I was about to say for those of you listening who are thinking about investing in a kill or a wheel, you know, I think if you do your research, you can feel better about that. These things aren't cheap, but if you do take care of it, it will last you. Hopefully 25 years like my kill and my wheel now that I think I'm a firm believer in buying the most kill that you can. You know that the most number of features and upgrades buy all those and buy a smaller kill and it will last longer. You know, as I treat our kill so badly, like I basically refused to do to me. But, you know, they're also well built. You know, people always like to freak out about like, oh, you can't fire the content. I fired a content all the time and all my elements last 250 firings at least. And that's what treating them like dirt. Like I don't go and repin elements ever. I let them sag and hang and all of that elements. Don't look to test that close to the element. Hey, it has nothing to do with my age and my drooping elements. Totally natural. Yeah. Totally. Oh my gosh. All right. All right. Thank you with drooping elements. We're ready to move on and start focusing on our listener questions. And so for our first one, you know what is one thing that I know about Marie from Norway? What's that, Gabby? Marie hates pinholes. Oh. Hi, Kate, Matt and Rose. My name is Marie. I'm a potter from Norway. And I have a question about pinholes. I hate them from the bottom of my heart. And I wonder how dangerous they are. It's so difficult to understand why they appear. There are so many factors. And the bigger ones that they crack, I mean, you can cut your fingers and that's not good. The smaller ones, they may not crack and they're just not pretty. Can you still use the pieces? I mean, if it's fired high enough and the clay is vitrified, is it okay to use? Or should they just go in the bin? Because I'm so tired of them. And these are the kind of pieces that I would use in my house instead of selling. But yeah, I'm so tired of the pinholes. Thank you, bye-bye. Wow. Well, I wish we knew what temperature, but although, you know, pinholes can happen at any temperature. Although it sounds like she's got more than pinholes. You can really feel that in our region, Rage. That was very, very angry. I had no idea really. Okay. Kathy, what do you do with pinhole? I mean, you've got to get them occasionally. Oh my god, no, she does it. Okay. I'm better than all of you. No, I don't that that is one flaw in my personal work. I do not get. I mean, no, I get I get crawling in and put what was it? Plucking? It rose. You taught me this plucking. Is it? Oh, yeah, with the sticks to the the shelf. Yeah. Yeah. Yeah, but we've got plenty of examples at the studio pinhole. And I think when I was a young and I was taught that it was because the piece wasn't best. Correctly. And that it often happened at low fire in both producer Ben and I worked with the mealica wizard Linda Arbuckle back in the day. So we heard about them a lot. I don't know if that's true, but. Yeah. And producer Ben, I mean, you are still a low temperature potter. You wrote the book on low temperature. Linda a lot of pinholes. I did it one time, but Biscayne is what fixed it. I've risked lower to have better particle packing, which solved one, solved the type of pinhole that I was having. But I think what Rose was saying is right. It sounds like she has blistering and pinholeing, which is like two different things. Exactly. No, no. No. Yeah. And that really is the big deal of something people need to understand is we almost need to banish the word pinholeing because pinholeing is presented as one flaw. And it's not one flaw pinholeing we have been able to identify as what I will say is four and a half different flaws that all occur for very, very different reasons, but they look so similar that everyone just calls them pinholeing. And this is the big problem of if you don't know why you're getting the flaw that you're getting, you're just wasting your time trying to fix the problem. Yeah, you're just chasing your tail because it doesn't go away. Yeah. Yeah. And so it is something where you really need to go and look at the possible reason. So the list really quickly is blistering, which is the one that is most commonly mistaken for pinholeing. And blistering is caused by the decomposition of iron or copper. Iron and copper as colorants are both have this problem where it's cone for they naturally change their chemistry and they release oxygen into the glaze. And it cone for pretty much every glaze from cone six to cone 10 is in the melting process. And that means you get bubbles that are released into the melting glass that swell and maybe heal and maybe don't. But you can you can really tell that sharp thing. They are the ones that will have a sharp broken edge because these bubbles if they pop they can sometimes fracture and leave a sharp edge. So that's why that sounds like that's the problem. And that can be iron or copper like look at your glaze recipe. Does it have copper iron in it? If you're using a commercial glaze is a green or brown? Because those are the colors that you're commonly going to get with iron or copper or red or red. And then it also can come from the clay body too because clay bodies often have iron in them. In fact, I would I fairly comfortable saying all dark bodies have iron in them. I seen a lot of people online recently trying to just say, oh no, my body is dark because it has manganese. No, no, no, that body is dark because it has iron and manganese just being used to tint the color to a particular shade. But so that's one. The next problem is a weird one that's called we call pitting, which is specifically associated with a material titanium, which may be root yield in your glaze. The one after that is is the sort of problem in a half which we'll call body voids or application voids, which are yeah, which is you'll never see them coming. But like your clay body can still have little air pockets right on the surface and you won't even see them. They're microscopic, but then glaze just doesn't cover it because there's literally no wear for the glaze to stick to. And then the the opposite one of the application voids is sometimes you get what you always get air rushing out of your bisqueer as the water's rushing in when you apply your glaze. It'll just make bubbles on the surface and then you know you might see them in the application, but you don't sort of smooth them over and it just stays as a void. And then the last one is actual pinholes and actual pinholes are an application issue. And it's what's called it's a particle packing issue. And what's going on is that when you apply your glaze, although it looks like a solid coating, it's actually anywhere from 30 to 50% air in between those individual particles. And when the glaze melts, that air gets trapped. And then the bubbles will swell and expand. And that eventually pop. And that's what classes causes the classic pinhole. And it's it's ramps. That's like melted in. So it's it's not it's not rough on the edge or anything like that. It's melted in to the body. Yeah. And that visual distinction is really important. Like when we're talking about the blistering thing blisters up close. Like if they have popped and collapsed and not shattered, what they'll often look like is like the glaze will be flat coming up to the edge and then there'll be like a little rise up and then it'll go down. Oh, I love looking those. Yeah, they look cool. But that's because the bubbles swelled and popped and then it sort of collapsed in on itself, leaving that ring on the edge. But you'll know generally like if it's got iron or copper and you're firing oxidation, it's definitely blistering. Um, you know, to the greater question as like, can you use them? Can you not use them? It's pretty much it's it's more up to you. Like theoretically, we'll just go and say I would not use the blistered ones. No, not blistered. Yeah, no, we'll use the blistered ones. Continue to fracture. Yeah. Just straight up pinholeing. I don't particularly care myself. If you assume the clay bodies vitrified, like like, you know, theoretically, that should be glassy and nothing should get through it. And like, we're all ceramicists like we all totally have pots in our houses that like have tons of flaws. And I mean, come on, how much how much of all of our personal collections are like pots that are friend of ours is like, yeah, this one's got some flaws that I bet you can have. I'll dig in. Yeah, my cabinets are like a second sale. Absolutely. Yep. So, but like I wouldn't sell it like it doesn't look good as like a product you're going to sell. And then the last one is like, can you fix it once it happens? I'm always of the opinion of just making a new pot. I wouldn't I wouldn't spend a lot of time trying to dab glaze on. But like, I don't know, Ben, did you ever try to do that when you were when you were getting those problems when you try to fix them or was it helpless? About one in 10 times I fixed it and that gave me false hope. So I kept doing it. But now I've decided that if you can't refire it once, like if you can't get a second glaze coat thick enough to fire it. If it doesn't get fixed after the second firing, the second glaze firing, just right in the trash with a hammer. Yeah. It's a lot more time wasted that you like, you know, how much time did you really spend like throwing in trimming it versus how much time you're going back trying to fix it again? Yeah. Well, what could I mean now I feel really bad for Marie and Norway. So is there like a tattoo because we love this. Is there a test test test moment that something she could try with changing her best temperature or and then test the glaze over it? Well, I think she needs to identify identify what which is the biggest problem she's experiencing kind of lower those variables that you have because if you're saying you have three different types, okay, which one is the most? Do I have iron and titanium? Do I have a dark body? Well, like you just need to figure out what you're using and what could be the problem and then go from there. The lady speaks the truth. I mean, this is the problem and this is why, you know, I was saying like the word pin-hoaling is doing all of us a disadvantage because it means you are not identifying the actual problem and why it's actually occurring. So yeah, look at the recipe. Like I said, if you can identify an iron or copper, the bad news about iron or copper is that there's not much that you can do about it. Like it's a thing like I won't pull out all the charts and graphs but like, thank you. Literally, the decomposition happens and it's well documented and this is one of the big things and I know people get angry when I talk smack about dark bodies but dark bodies are always going to do this. If you're firing over cone four, I do not care what special firing you've done. I don't care about your magic bisque until it smells clean. Iron will do this. Full stop and so like just you need to know that. Like it's going to consistently be a problem. Copper will do it full stop and you know there are some glazes that'll heal better and sometimes oh it didn't happen in like five Fire's then it happens because it's just it's it is one of the things it is unavoidable Inoxidation so you have to know why you have these problems and then you can sort of go about fixing them You know as far as the the testing yeah, it's definitely a thing where Some things will make it better You know Ben was talking about Changing this temperature now. This is one that Ben is doing exactly what I would advocate and a lot of people will fight on this one Because the constant the constant advice you will see online is oh you should bisk hotter Oh, you should bisk hotter. You're not getting a clean bisk Let's be clear everybody. There is no such freaking thing as a clean bisk That is a lie everyone is telling It is absolutely not a thing. I have got so much documentation. It's not even funny That everything that quote unquote burns out of a clay is gone by 850 c Which is Kono 12 and that is that is the reality So when people are talking about a clean bisk they're not talking about what they think they're talking about and The advantage that you get from bisking to certain temperatures in one of my big things is always bisking lower Is changing the porosity of your bisk which is gonna change the absorption rate? Which is how the glaze applies and that's a huge deal but not a clean thing but but Ben you know that I thought No, your hand actually raised because you were doing like this and it made Was listening it's we you know Matt can get animated and triggers the the zoom raised my hand I can which is always funny and so I just wave back at him It's good, but I did coincidentally have a thought which is beyond bisking lower one of the things it was causing it for me As I was deflaculating my slip Which was making the slip barrier on top of the clay tighter which then made the glaze absorption less Which was giving me more pinholes So I stopped deflaculating the slip and I just got I guess what would be like the actual Capillary suction of a lower bisk and it I've never had that problem since Wow That one Yeah, and that's a huge deal and I think we've talked about it before with under glazing of One of the things people will constantly complain about is that the glaze doesn't code as well on their under glazes And so like the glaze would be nice and smooth and also none of the other glates. It's like chunky and weird dry Yeah, what is going on is that your application depends on the absorption rate of your bisquare and That under glaze has got a different absorption rate than your bisquare So you're gonna get a thicker coating on the raw clay than you will on the under glaze You're literally just getting a thinner coating of glaze and that'll look you know funky because it doesn't have a complete coating And so for like things like that I always advocate biscuing on your under glazes because at least it'll more normalize the absorption rates So that you get a more consistent application Well, this is a good example Marie from Norway and other listeners like Marie Pretend you're on a dating service and when you call us give us some stats Tell us a little bit about yourself. Are you oxidation reduction? What temperature are you going to? What does your clay look like? What kind of glazes do you use and then we've got some meat to the bone To get into but still we appreciate all our questions So let's go on to another one and our next question has to do with something you mentioned earlier Manganese and this question comes from Piper from Montana state in the states This is Thomas. This is Carson. This is Piper. This is Jenna. This is Ella and this is Rose Shriver I'm a visiting professor at Montana State University and we are a Intermediate ceramics class and we're calling in with the student Piper Landon with the question take it away Piper All right, so in class We've been doing working on glaze chemistry and learning about what makes a Tomic structure of glass in glazes and I've been working with this glaze that is heavily metal and has is about Yes, 70 to 80 percent metal and has a ton of Manganese dioxide in it and I'm wondering at what point a Glaze just becomes a melted metal I love it group questions. This is great. Is it good one? On 10th state I teach him on 10th state from time to time. I was just talking to Josh. Do we use one of the Josh and Jeremy out there, so it's good to hear from the students out in Montana It's a great question. I have to start with asking Kathy a question Kathy what what makes a metal I don't know The material is made out of the Element the metal element that's it. Okay, so we commonly know things as like iron is a metal right and certain materials can make a metal But in ceramics we use iron in the form of red iron oxide Is that iron a metal Maybe My poor wife's a blacksmith. She's gonna be so disappointed. All right. Okay. I'm really gonna break your brain. Is Telsium a metal now Really We got it we got to take a step back and you know the reason why I asked this question is a really important distinction on on What materials are and how we use them and what their chemistry really is a Metal is an element on the periodic table that can participate in what's called metallic bonding and that's where an element can bond to itself Okay, and that creates a relative stability chemistry is all about creating stability between elements So you can bond an iron to an iron you can bond a Copper to a copper and those will make a metal well the thing is is that 64% yes, I have that number memorized 64% of the elements on the periodic table will make metals and that includes things that nobody thinks about like calcium or Or or basically anything that is to the left of Silica will make a metal on the periodic table Everything so sodium or lithium or calcium all of those are metals the catch is is that in ceramics we don't use metals We use oxides of metals where those materials have been stabilized in their oxide form And this is a really important detail because interestingly enough in ceramics the materials that we use at least in art ceramics They have to be oxides not metals So I bring this up I bring up the calcium point because everybody hears like oh, I'm using manganese and my glazed using iron and my glazed I'm using metal and my glazed no no you're not no you're not everybody Because you're using an oxide you're using an oxide of an element and like yes We commonly think of things like manganese or iron is metal because people interact with them in their metallic form in day-to-day life But calcium's a metal - and nobody's freaking out about calcium being a quote-unquote metal Why does this matter because the glaze that Piper's talking about is one we call a fake bronze And a fake bronze is a glaze and it's a straight-up glaze. It is using oxides She even mentioned manganese dye oxide. Okay, that is telling us that the manganese is bonded with oxygen Well, the interesting thing about ceramics is that we can't use metals in our atomic structures We can only use oxides And so the second something does become a metal it actually doesn't interact with our chemistry At least in art ceramics there are a couple of special examples in like high-end ceramics where they can do that But then in what we do Everything is in the oxide form So these fake bronzes do they look metallic? Yeah, if you want to be generous with their approach, but they are absolutely not metallic They are a glass with crystals growing inside of it In fact, they're what we would classify as a crystalline glaze Now the interesting thing about how these work is that the fake bronzes do use a lot of manganese that is true But and most people think of manganese as a colorant But manganese actually is not a colorant under this really specific definitions Colorants are materials like people say like oh, yeah I just like add in some cobalt to my glazed and it makes it blue And then they sort of ignore the chemistry of what's really going on Well, yeah, like is cobalt a colorant sure Does it contribute to the overall chemistry of their glaze? Like people in ceramics tend to ignore it and say yeah, I don't need to worry about it No, no that cobalt or that manganese is a hundred percent contributing to the chemistry of your glaze You're just using so little of it. It doesn't make a huge change But if you add a lot of it, it absolutely will And the interesting thing about some materials like cobalt and iron and manganese is that in our glazes, they actually function as alkaline earth fluxes. Okay, so all of our glazes have two fluxes and alkali metal and alkaline earth. Historically, the list of alkaline earth fluxes is magnesium, calcium, strontium, barium, and zinc. And if you ask most people, they'd say those are the alkaline earth fluxes. Yeah, that's actually not a complete list because that list continues on to lead. That is an alkaline earth flux. We just don't talk about it. And then cobalt, iron, and manganese that yes, those are materials that provide color, but they also behave as alkaline earth fluxes. And when you use a lot of them, they just behave like a normal alkaline earth flux, but they do also happen to make a color. And when they crystallize, they'll make these crystals that look bronze. But it is never, never, never, never turning into melted metal, which was what Piper's question is. It is always staying a glass with crystals growing in it made out of oxides. Okay. And this is a huge, really, really important distinction that everybody needs to hear because it's like I hear it all the time about like people freaking out about metals in their ceramics. There's always metals in, it's never metals in our ceramics because we're dealing with oxides not the metallic form. It is a completely different chemistry of thing. And that's a subtlety that most people are just bypassing, but is utterly imperative for understanding what we do. It makes for an expensive glaze. I know that because we had a bronze glaze for the studio and then God bless glazy.org because one of the staff plug all our costs from our supplier and then we can literally see how much that bucket of glazes and I was like, oh, nope, nope, nope, nope, nope, nope, nope, that was a little duke that's a very good thing because you can buy it in a bottle now. Well, you really want a pucker. So, so all of this concept comes from something that Rose and I developed several years ago that we call the experimental UMF. And the UMF is the language we use to look at glaze chemistry. And one of the things that we dealt with for years is this notion that like, well, yes, you have your base glaze and then your color and search just on top of it, right? We're always the type of people where like, you know, you'd be hanging out when you're a young person, you're hanging out with somebody super smart and they'd go like, well, yeah, like, you know, like copper is a colorant. And but it's also, but copper is a flux. It totally fucks as your glazes. And we'd be like, yes, and continue. Can you please explore that concept? And no one would ever bother to explain it except, yeah, you know, copper fluxes. And so after a number of years, like we just got tired of the nonsense of people in the community like making these declarative statements, but never having the chemistry to back this up. So we then started to look at these ingredients that people attribute as colorants, but don't give any chemical attribution to because they're just like, oh, yeah, it's just on top. Like if you know anything about chemistry, you know, nothing is ever just on top. It is either part of the chemistry or it is not. Now you may be ignoring its role on chemistry, which is what everybody's been doing, but that doesn't mean it's not contributing. So like, yeah, when people say, oh, copper is a flux. So anyway, so years ago, Rose died side of like, we're going to make these definitions. We are going to define like what they are. And this is where the experimental you don't have came from. And what we found is is that cobalt and manganese and iron are all alkaline or fluxes. So what this led to is us developing some crazy glazes out there. And one of the glazes that we invented is what's called the cobalt crystalline glaze. And the cobalt crystalline glaze came from a very basic concept. So we had discovered that cobalt just works like calcium. You can just like use it, but you need a lot of cobalt to replace calcium. Like if you look at your glaze recipe, it's got, you know, if your glaze has like 20% of the white ink, you're going to need actually more than 20% cobalt to have the same number of molecules. And so long after we discovered this, I'd ask myself a question, which is like, okay, well, like if cobalt plays the same role in a glazes calcium, and I can make calcium crystallize, can I make cobalt crystallize? And the answer was like, yes, 100% you can. Like because it just does all the same things that calcium does, cobalt will do it. And then the same thing came up with the manganese. Like, well, manganese is an alkaline earth. Could I make manganese crystallize? The answer is yes, that's what the fake bronzes are. They're literally manganese as an alkaline reflux, and then as a crystalline glaze on top of it. Well, the cobalt crystalline glazes, they really got taken and run with by a student of ours named T.C. He goes by cone infinity on Instagram. And T.C. he really started taking them and doing some really, really wild things with them. And they got him for it. But the catch with T.C. is with these cobalt crystalline glazes is that they're going to be like 30% cobalt via weight. God, I know. I'm thinking to myself, do you guys all have money to burn? Is it billionaires? And you're like, what can I do with all this money? I'll buy cobalt. T.C. I will say lives a dream because T.C. lives in Hawaii. And he has a family business running a sod farm. And there's not a ton of maintenance that takes to build a sod farm. So T.C. built a ceramic studio at the sod farm. And like he literally just watches the glass grass grow in Hawaii. Literally. And like test glazes. And he was like, I'm going to commit myself to this cobalt crystalline. And he spent a massive amount of money. My gosh. Ton of cobalt. But he came up with really incredible things. And I will say that there are some people out there recently who've been trying to like make cobalt crystalline glazes their thing. Uh uh. No shame on you. Cobalt crystallines were invented by us. We're mastered by T.C. and you were just a co-tail rider. So yeah. No, no. I've heard it in your first. And cobalt crystallines. Those are C.M.W. and T.C. cone infinity. Well, all right. Mike dropped Matt. Okay. Well, thankfully, that is all the time we have for today. Hello. Enjoy your summer, Matt and Rose. Stay out of the water. Later, Kathy. Later, Kathy. Well, folks, that's it for this week's episode of For Flux Sake. I'd like to thank the listeners who submitted questions this week. And if you want your question answered on the show, shoot us an email at For Flux Sake podcast at gmail.com. So join us next time and win in your studio. Remember what Rose always says. Always remember to test test test. This is a test of the emergency glazed system. Beep.

Podcast Summary

Key Points:

  1. Ceramic equipment like kilns and wheels can last decades with proper care, though quality and maintenance vary.
  2. Pinholes in glazes are not a single flaw but multiple issues (blistering, pitting, body/application voids, true pinholes) with different causes.
  3. Blistering is often due to iron or copper in clay or glaze decomposing during firing, especially in oxidation above cone
  4. True pinholes result from particle packing issues during glaze application, where trapped air bubbles form during melting.
  5. Identifying the specific cause is crucial for effective fixes; solutions may include adjusting bisque temperature or glaze application methods.
  6. Flawed pieces may be usable personally if vitrified, but are generally not suitable for sale; repairing them is often less efficient than making new pots.

Summary:

The podcast discusses the longevity of ceramic equipment, noting that kilns and wheels can last 25-30 years with care, though maintenance varies. The main focus is on addressing pinholes in glazes, emphasizing that "pinholes" encompass multiple distinct flaws: blistering from iron/copper decomposition, pitting from titanium, body/application voids, and true pinholes from particle packing during glaze application. Blistering, common in oxidation firings above cone 4 with dark clay or colored glazes, is often unavoidable.

True pinholes relate to glaze application density. The hosts stress identifying the specific cause to apply correct fixes, such as adjusting bisque temperature or glaze consistency. While flawed pieces may be used personally if vitrified, they are not ideal for sale, and repairing them is often less efficient than creating new work.

The discussion underscores the importance of understanding material behavior to reduce frustration and improve outcomes.

FAQs

With great care, ceramic equipment can last decades—kilns and wheels may function for 25-30 years or more, as shared by the hosts who have used their original equipment for many years.

Pinholes are small flaws in glazes that can result from various issues like blistering from iron/copper decomposition, pitting from titanium, body voids, application voids, or particle packing problems during glaze application.

If the clay is vitrified and fired high enough, pieces with small pinholes may be safe for personal use, but they are often not suitable for sale due to aesthetic concerns.

Examine the glaze recipe for iron or copper, check if you have a dark clay body, and look at the pinhole characteristics—sharp edges may indicate blistering, while smooth edges could point to application issues.

Blistering is caused by iron or copper decomposition during firing, creating bubbles that may pop and leave sharp edges, often mistaken for pinholes but stemming from material chemistry.

Identify the specific cause first—adjust bisque temperature, improve glaze application to avoid voids, or modify materials if iron/copper are involved, as some flaws are inherent to certain clays or glazes.

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