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I'm having severe cracking problems on large 20 inch platters. I think it's from hairline cracks developing during drying. The platters were dried upside down for about four months inside large plastic bags. Every week or so I would open the end of the bag and flush some fresh air through to clear out some of the condensation on the inside of the bag. Some of the platters were thrown in the traditional pull a cylinder and spread it out technique. Others were made from a slab laid on the bat on the wheel head. It doesn't seem to make any difference which way they were made. Attached are pictures of various styles of cracks. Suggestions please

Hello All! I've been trying to make cake plates for a while in my new studio, they just keep breaking in the kiln and I can't figure out why. I've attached a photo from my sneak peak earlier, I dried it super slow and there were no signs of stress after bisque firing. My pottery dictionary doesn't seem to match this type of crack, so I thought I'd ask you wise people. Thanks in advance! Sarah

Hi, We have been doing the jigger for the first time and the pieces whatever we are making have a cracks in a same pattern in a same location, and we are using Terracotta clay to make the pieces and here I m attaching the cross sectional pieces of the molds., and in the molds I have few doubts and I would like to get clarified so that I can reduce the cracking doors one by one., Does the thick and thin portions of the molds absorbs water differently so that the pieces are cracking ? As you can see the picture of the pieces the cracks are happening in the place where the side wall is connecting with the curved edges, and the cracks are happening only with our terracotta clay and we have tried quite a lot of receipes to avoid cracks but nothing is helping out and the cracks are happening in the inside of the pieces and the outside wall is just fine. Also we have tried jiggering few pieces with our stoneware clay and we havent have any cracks in the stoneware. Does the uneven wall thickness is the reason to get the cracks ? Wi only the Terracotta is cracking and not the stoneware ? Wi the inner wall is cracking and it didnt extend to the outer wall ? Does it anything to do with the plasticity and the composition of the clay? As far as the design is concerned, we make sure theres no undercuts in the design and even the wall is not striaght and it has an angle of 10% for easy releasing., we used to have few issues with our clay body which I was working with Tom (Glazenerd) to solve the issue, but apart from that I would like to know what are the other possible reasons for the cracking.

I've watched a lot of videos, and I still don't get it. "Trim your pots when they are LEATHER HARD." "Attach handles when mug is as soft as possible." SO which is it? If things are too dry, or if there is too much difference in moisture content of mug and handle you can expect cracks where the handle meets the mug.. I'm getting my fair share of them. Maybe the answer is to throw mugs that are perfect and need no trimming. RIGHT. I'm using stoneware clay from Standard. How can I avoid cracks. How am I supposed to repair cracks before firing? ja

Hi, I have this problem of cracking or clay splitting when throwing in the wheel, pls find the attached picture and also, after firing at cone 08, the clay has a lot of surface cracks and sometimes structural cracks pls find the attached pic, pls advise why this is happening and how to avoid this in future. Thanks.

Hello! I had a couple of pieces that, freakishly, dried just fine...evenly...even thickness...all around good slab pieces... cracked in the kiln! I fired at the correct temp and somehow this happened. I've read about magic mud...and I was under the impression that it could be used on bisque fired pieces. However, my instructor told me that it couldn't? I wanted to see what everyone thought?

Hi, I would like to ask you for help regarding some trouble with cracking bottoms of my pieces in the kiln.effect that is not described below. When I fire in my electric kiln I can observe that the bottoms of the bodies get stack to the shelves or just crack at the bottom. See the picture here<https://1drv.ms/u/s!AkzUYiXaPPNa3TZ80pGXEUeQBfob> (often there are more severe and damaging cases) So, I think it is not: - Overheating above clay limit as I happened to different clays including porcelain. In all the cases the clays were supposed to survive the temperate of the firing (about 1230 C). - Overheating due to broken controller, because no other signs of it, it happens on every shelf. - Shelf wash because I changed it 3 times I wonder how to avoid this problem? What is the root cause? Maybe the atmosphere from the glazes or wrong heating curve (usually 80C/h to 600C, 120C/h to 1230C, 20min, skip)? Can you share your opinion? Thanks in advance

I have been using the same clay,slip and glazes purchased from a local ceramic shop. Everything has turned out beautifully but I got a new mug mold that will NOT stop giving me issues! The mug is slip cast using low fire slip. I fire to bisque..all good. Then I apply my glaze and fire..I let the kiln cool for at least 12 hours and still around the rim and handles I keep getting light crazing. No matter what I do..less glaze, more glaze, longer firing, soaking on high, the mug will still craze. Keep in mind, I haven't changed anything from the other ceramics I'm glazing, which all turn out without crazing, just the mugs are crazing. It's weird and I can't seem to figure out why or what I can do to keep this from happening. If you need any other info just let me know. I have a ceramic shop and really need to fix this issue asap! -Casi

Hi folks, again we have another quiz based on a book. I chose some of the questions this week to clarify terms that I have heard potters use interchangeably when they shouldn't be, so be careful. Week 7 _______________ is the ability of liquid to penetrate and be distributed through a material. It specifically relates to the working action of a dry clay surface when in contact with water. Porosity Shrinkage Marbling Absorption _______________is the quantity of the pores or voids in a clay body. Porosity Shrinkage Marbling Absorption _________ _____ is caused by a contamination in the clay, best described as a half moon shaped pit in the pot, with a light or dark nodule in the center. This can occur immediately after firing, or several years later as calcium chloride expands. Contaminated grog Lime pop Alkali salting Wet blistering Preventing S-crack formation in pottery in thrown pottery is dependent on __________________ alignment of the clay platelets during the throwing process. Much of this is dependent on the coning , opening up, and compression stages of the throwing. Linear asymmetric concentric random This weeks questions were taken from text in The Potters Studio Clay & Glaze Handbook, Jeff Zamek, 2009. Quarry Books Note from Pres: I could have gathered hundreds of questions from this book, but chose those which I thought would be of interest to the largest audience. I believe that I will return to some books after some time to add more. For those of you interested in glazes, and clay bodies, this is a well constructed and informative text. Answers: Absorbency and Porosity (Answers to both 1 & 2 are included in the text here) 1. (d) Absorption 2. (a) Porosity Two terms that are frequently used interchangeably but describe different conditions ore absorbency and porosity. Absorbency is the ability of liquid to penetrate and be distributed through a material. It specifically relates to the wicking action of ct dry clay surface when in contact with water. Porosity is the quantity of pores or voids in a clay body. ( Lime pop occurs when moisture in the air comes into contact with a carbonized lime nodule, causing its expansion in an unyielding tired clay body. This can occur when the pottery is removed from the kiln. li can also happen years later, as lithe expands (in the torm at calcium hydroxide). Lime pop is a semi-elliptical 1/8- to 1/2-inch (3- to l3-mm) crack in low-temperature bisque or high-temperature fired ware. A conical hole reveals a black or white nodule (lime) at the bottom. © concentric See image below.

I have just poured the inside of a stoneware cylinder (test piece bisqued to 1000oC) with a transparent glaze that crawled horribly in a previous batch. This is a commercially mixed dipping glaze - very reliable by all accounts! Following advice here and elsewhere I let it stand and drew the excess water off the top. The glaze is now like pouring cream consistency. 100ml weighs 153g. I've poured the inside - about 3 seconds. As it dried the glaze cracked - see photo. What does this indicate? Can I just finger-sand it and dip the outside or am I destined for more disappointment?

Hi there, I recently bought my very first kiln. It's VERY old, I think from the 60's or 70's. I was assuming it would have cracks in it, but I am a little concerned about the condition of the firebrick on the top. It's so crumbled it's almost falling into the kiln. I've seen a few websites that say the cracks don't matter unless the elements are sagging because of it, but I just find it hard to believe that with it this damaged they can still insulate (especially at the top). I've attached a picture of it. Can anyone tell me if I need to repair these bricks or not? Or does it just not matter if I can still get to temperature alright? Thanks in advance, Sigourney