Troubleshooting

29 pages

• Black CoringBlack Coring A common fault in reduction gas fired ceramic ware made from iron bearing clays. The interior cross section of the clay turns black. Details For potters, who use periodic kilns and slow firing schedules , black coring almost…
• Bleeding ColorsBleeding Colors In ceramics, the edges of overglaze and underglaze color decoration often bleeds into the over or under glaze. How can this be avoided. Details Overglaze decoration (and frequently underglazes ) often bleed on the edges,…
• BloatingBloating Bloating occurs when the off-gassing of decomposing particles in a body has not completed by the onset of density and impermeability associated with the vitrification process. Details Body bloating (larger bubbles) and blistering…
• Casting Slip ProblemsCasting Slip Problems Casting slips are deflocculated in order to reduce water content. It is important to understand this phenomenon and know how to assess a slurry to know what it needs. Details Assuming that the casting slip recipe…
• Chrome Flashing in Ceramic GlazesChrome Flashing in Ceramic Glazes The development of chrome tin pinks is a combination of the stain and the right chemistry in the host glaze. Unwanted pink flashing occurs where there is a hostile chemistry in the glaze. Details Close…
• Clouding in Ceramic GlazesClouding in Ceramic Glazes There a many factors to deal with in your ceramic process to achieve transparent glazes that actually fire to a crystal-clear glass Details It seems logical that a transparent glaze would fire transparent (or…
• Cracking of Clays During DryingCracking of Clays During Drying The best way to avoid drying cracks when making ceramics or pottery is to avoid doing the things that cause it. Do not just blame the clay, anything can technically be dried. Details Here are some factors…
• CrawlingCrawling Ask yourself the right questions to figure out the real cause of a glaze crawling issue. Deal with the problem, not the symptoms. Details Crawling is where the molten glaze withdraws into 'islands' leaving bare clay patches. The…
• Dunting and Cracking of Clay Bodies During FiringDunting and Cracking of Clay Bodies During Firing Ceramic industry can fire much faster and deal with much heavier objects than potters can, how do they do it. The answer is they pay more attention to the basics, it is all common sense and…
• Foaming of Ceramicd Glaze SlurriesFoaming of Ceramicd Glaze Slurries Ceramic glaze slurries can sometimes generate enough foam that it becomes difficult to apply an even layer to a surface. What can you do? Details Some ceramic glaze suspensions will foam as they are mixed…
• Glaze BlistersGlaze Blisters Questions and suggestions to help you reason out the real cause of ceramic glaze blistering and bubbling problems and work out a solution Details Blisters are evident on the fired glaze surface as a 'moonscape' of craters,…
• Glaze CrazingGlaze Crazing Ask the right questions to analyse the real cause of glaze crazing. Do not just treat the symptoms, the real cause is thermal expansion mismatch with the body. Details The fired glaze exhibits a network of fine cracks. These…
• Glaze is Off-ColorGlaze is Off-Color Questions to ask and strategies to try in dealing with glazes that do not fire the expected color or have stains or discolored areas Details If your fired glaze is not the expected color here are some questions to ask.…
• Glaze Marks or ScratchesGlaze Marks or Scratches Questions to ask and strategies to try to deal with glaze cutlery marking, that is, glazes that are too easily scatched by metal. Details 'Cutlery Marking' occurs where metal instruments leave marks on glazed…
• Glaze peeling on dryingGlaze peeling on drying Happens as clay-containing glazes shrink during drying on the bisque ware, first cracking then pulling away. Details A common problem with dipping glazes . Glazes contain clay, so they shrink when they dry. There is…
• Glaze Pinholes, PittingGlaze Pinholes, Pitting Analyze the causes of ceramic glaze pinholing and pitting so your fix is dealing with the real issues, not a symptom. Details 'Pinholes' are small holes in the fired glaze surface penetrating down to the body below,…
• Glaze ShiveringGlaze Shivering Ask the right questions to analyse the real cause of glaze shivering. Do not just treat the symptoms, the real cause is thermal expansion mismatch with the body. Details Shivering is the opposite of glaze crazing , the…
• Glaze Slurry is Difficult to Use or SettlingGlaze Slurry is Difficult to Use or Settling Understanding glaze slurry rheology is the key to solving problems and creating a suspension that does not settle out, applies well, dries crack free. Details We often tend to put so much effort…
• Leaking of Fired CeramicsLeaking of Fired Ceramics Details This problem is often called "weeping", or just "leaking". To guarantee water tightness a clay needs to be vitrified to be dense, thus have a low porosity (typically less than 1%). If a glaze is not crazed…
• Lime PoppingLime Popping Details A body firing problem where particles of calcium sulphate in the fired or bisque fired body slowly absorb water from the air, expand, and pop out a section of the body. These particles can be contamination or naturally…
• Orange Peel SurfaceOrange Peel Surface Orange peel is a defect or physical property of ceramic glazes Details Ceramic glazes can have a surface texture like orange peel , this can be intentional or a defect. Matte glazes, depending on their mechanism , can…
• Over Firing of Ceramic Glazes and BodiesOver Firing of Ceramic Glazes and Bodies Overfiring can happen with glaze, engobes or clay bodies. The problem is more subtle than you might think. Details This can happen with bodies, engobes or glazes. It can be more subtle than you…
• Powdering, Cracking and Settling GlazesPowdering, Cracking and Settling Glazes Powdering and dusting glazes are difficult and a dust hazard. Shrinking and cracking glazes fall off and crawl. The cause is the wrong amount or type of clay. Details Glazes in traditional ceramics…
• Runny Ceramic GlazesRunny Ceramic Glazes Glazes of high melt fluidity are likely to run if applied to thickly or have not catcher glaze Details Glazes melt. If they do not melt enough then the surface is not glassy and smooth and easy-to-clean. It stains ,…
• Specking on Ceramic WareSpecking on Ceramic Ware Specking, or speckling, can be both a fault or feature in fired ceramic ware - caused or produced by metal-bearing contaminants to metallic additives Details A common surface defect in fired whiteware and porcelain…
• Splitting at the Plastic StageSplitting at the Plastic Stage Pottery clays can split at the plastic stage, sometimes ware can fall down right in front of your eyes. Why? Details If clay bodies are made from too high a percentage of plastic materials they shrink too…
• Staining of Fired Ceramic GlazesStaining of Fired Ceramic Glazes Ceramic glazes are glass. That means they are always easy to clean, right? Wrong - because the surface is not always glassy. Details Ceramic glazes are glass and thus should be micro-smooth. If they are not…
• Uneven Glaze CoverageUneven Glaze Coverage The secret to getting event glaze coverage lies in understanding how to make thixotropy, specific gravity and viscosity work for you Details In industry alot of effort is put forth to create glaze slurries that cover…
• WarpingWarping There are multiple reasons why pottery and porcelain pieces can warp during firing, both vitreous and non-vitreous ware. Here is what to do about it. Details This normally refers to a body firing problem where vessels warp…