Question:

How do I avoid S cracks in wheel thrown ware

Avoiding s cracks

Have you ever had trouble with cracks developing in the base of your wheel thrown work? This problem can be avoided by following a few simple guidelines.
Cracks develop for two main reasons: uneven drying and uneven compression in the throwing process.
 Avoid uneven drying
OK, so you put your wheel thrown work in a drying cupboard. You even additionally cover the work with plastic sheeting, trying to ensure even drying. But if you are throwing on a bat, no air reaches the bottom of a platter, vessel or other thrown object. What happens? The top dries a bit slower. As the top dries, it shrinks and pulls together, cracking the slightly wetter and therefor larger surface at the bottom. Once a crack has developed, it is near to impossible to get rid of, even by turning (trimming). One way to avoid this might be to turn over the work halfway in between the drying process, but this is not usually feasible. So what to do? How to get that bottom drying at a similar rate? The answer: throw your work on plaster bats. (How to make plaster bats will be the topic of a feature soon to come.)
The bat will need to be moistened, otherwise the clay will pop off too soon and throwing will become an impossibility. After throwing your work, the piece can be lifted off while still on the bat, and the bat, work and all, can be placed in your normal drying area. After a few hours, depending on moisture content of the bat, the work will pop off all by itself, and may even be ready for turning that same day.
 Avoid uneven compression when wheel throwing
Cracks may not appear until in the firing itself, often even until a second high temperature firing, especially in fine clays like porcelain or porcelaineous stoneware. Rougher clays like raku are generally not so prone to cracking, unless you really treat them badly, as the grog tends to absorb a lot of tension. For finer clays, the best technique to get a consistently compressed clay throughout is to center the clay on the wheelhead, then cut off the clay with a cutting wire. Invert the clay and recenter 'upside down'. This ensures that the clay will be quite compressed at the bottom as well as at the top.
Combined, these two techniques should be able to cure most cracking problems with wheel thrown work

Introduction

Wheel throwing with standard clay. Again, a kiln is required. And once you are an experienced thrower you will undoubtedly want a large kiln, since you will produce pieces much more quickly than in hand-building. However, at the beginning I would recommend joining a class if at all possible. You can learn to throw from books or even better, videotapes, and some people do. But it is difficult. It takes a while to get the knack for throwing, and can therefore get frustrating unless you have interaction with an instructor and see other students struggling as you are. I think most people with no experience, buying a wheel and trying it out on their own, would get frustrated and give up. A class will offer you instruction, a kiln, and glazes so you don't have to worry about that quite yet. Your only investment will be the cost of the class, and perhaps some materials costs such as clay and a basic tool set for under $20. At some point you may find that you don't like to be constrained by the hours of the class, that you want complete control over your work (so someone else doesn't smudge the glaze, break, damage or steal your pieces), or that you want to do things beyond the capability of our class studio. At this point I would recommend getting your own wheel, and kiln unless you have access to someone else's kiln. However, if you are patient, you could continue to build your throwing skills, never firing anything but instead recycling the clay to be thrown again. It is tempting to want to finish each piece at the beginning, because you are very proud of it, but soon you will hate the look of those early pieces! so not even firing them at all would be a fine strategy. While you are in the intermediate stage, assuming you are firing your work, I would recommend an extruder. The reason is that you can make use of the hundreds of small cylinders you will throw, by putting nice handles on them and making mugs. Otherwise practice making hand pulled handles (shown in most pottery technique books.)

avoiding cracks through uneven drying

Have you ever had trouble with cracks developing in the base of your wheel thrown work? This problem can be avoided by following a few simple guidelines.

Cracks develop for two main reasons: uneven drying and uneven compression in the throwing process.

Avoid uneven drying
OK, so you put your wheel thrown work in a drying cupboard. You even additionally cover the work with plastic sheeting, trying to ensure even drying. But if you are throwing on a bat, no air reaches the bottom of a platter, vessel or other thrown object. What happens? The top dries a bit slower. As the top dries, it shrinks and pulls together, cracking the slightly wetter and therefor larger surface at the bottom. Once a crack has developed, it is near to impossible to get rid of, even by turning (trimming). One way to avoid this might be to turn over the work halfway in between the drying process, but this is not usually feasible. So what to do? How to get that bottom drying at a similar rate? The answer: throw your work on plaster bats. (How to make plaster bats will be the topic of a feature soon to come.)

The bat will need to be moistened, otherwise the clay will pop off too soon and throwing will become an impossibility. After throwing your work, the piece can be lifted off while still on the bat, and the bat, work and all, can be placed in your normal drying area. After a few hours, depending on moisture content of the bat, the work will pop off all by itself, and may even be ready for turning that same day.

Avoid uneven compression when wheel throwing
Cracks may not appear until in the firing itself, often even until a second high temperature firing, especially in fine clays like porcelain or porcelaineous stoneware. Rougher clays like raku are generally not so prone to cracking, unless you really treat them badly, as the grog tends to absorb a lot of tension. For finer clays, the best technique to get a consistently compressed clay throughout is to center the clay on the wheelhead, then cut off the clay with a cutting wire. Invert the clay and recenter 'upside down'. This ensures that the clay will be quite compressed at the bottom as well as at the top.

Combined, these two techniques should be able to cure most cracking problems with wheel thrown work.

Ceramics Frequently Asked Questions

What precautions should I take in the studio?

How do I decorate my ware?

How do I apply Lustres?

How do I market my ceramics?

How do I apply glaze?

How do I market my ceramics?

How do I fire porcelain?

How do I cast slip?

How do I fire an electric kiln?

How do I apply glaze?

What are some stoneware glazes?

What Precautions when using dry ingredients?

How do I apply glaze?

How do I apply opaque stains ?

How do I wedge clay?

How do I apply Stains?

What is Lustre?

What should I keep in mind when designing my studio?

How do I make a coil pot

How do I decorate my ware?

How do I make molds?

What is Clay?

How do I apply glaze?

What is a decal?

How do I clean Greenware?

How do I add texture?

How do I centre my clay?

What tools do I need to start potting?

How do I start a business?

How do I best promote myself and my work?

How do I load my kiln?

What are ceramics

Where do I start?

How do I make a simple mold?

How do I fire Decals?

How can I make a mould?

What are some life quotes?

What is underglaze?

What is Porcelain

How do I care for my brushes?

How do I care for my molds?

What is Celadon?

What is the Tea Ceremony?

How do I care for my kiln?

How do I apply one-strokes?

What safety aspect should I keep in mind when working with glazes?

How do I apply Lustres?

What is Overglaze?

What are oxides?

How do I fire Bisque?

Where do I begin?

What should I remember when firing the kiln?

How do I clean brushes?

How do I slump/sag glass?

How do I apply overglazes?

How do I best publicise my business?

How do I make a simple plaster mold?

How do I care for my brushes?

Are stains safe.

How do I fire overglazes/lustres?

What is a reduction firing?

How do I doccument my work?

How do I create fine feature lines?

How and when sholuld I apply underglazes?

How do I make molds?

What is an engobe?

Are they Water or oil base stains?

How do I hold my brush?

How do I store my Materials?

Are any two kilns are exactly alike?

What is mould in clay?

What is a Pyrometric Cone?

Do I need a cone?

how do I throw clay?

Can I use sand to stop glaze running onto shelves

How do I test my glazes?

How do I apply China Paints?

Does greenware need to be dry before loading?

What are some life quotes?

What is the history of the Potter´s Wheel?

How do I fire lustre?

What is a glaze?

How do I fire lustres?

What is The History of the Way of Tea

What is Celadon (Cheong-Ja) - the Stuff of Kings?

How do I dry overglazes?

What is a glaze?

How do I Burnish?

What is an overglaze marbleizer?

Is there a trick toThrowing Porcelain?

Have you some lovely words?

What is Earthenware?

What is a glaze?

What are some stoneware glazes?

How do I paint Eyes?

How do I Recycle Clay

How do I attach wet pieces?

How do I make a teapot?

How do I make a plaster mold

What are some good tools for decoration?

What is Kiln Wash?

How do I glaze my ware?

How do I slipcast ceramics?

What are some life quotes?

how do I dry my ware?

How do I fire my ware?

How do I apply texture to my piece?

What is a Glost firing?

How do I make my own glazes?

What are some change quotes?

How do I store my tools?

What is the history of Raku?

What is Paperclay

What is a crackle glaze?

Do I need kiln wash for bisque?

How do I refire a glazed piece ?

What is reduction?

What must I remember when Raku firing?

How do I add decoration to my ceramics?

How do I care for my elements?

Does over firing produce poor colour in coloured glaze?s

How do I use my brush?

How do I care for my brushes?

How do I recycle clay?

What are some success quotes?

What is a glaze?

How do I clean Greenware?

How do I make coils?

What are some Black Firing Tips and Tricks?

What is the safest way to pack my ceramics?

What are Formulated clays?

How do I do a reduction firing?

automatic kiln sitter, should I trust it?

How do I care for my molds?

What are some tips for draining a mold?

What is a decal?

What safety measures should I take with Raku Firing?

How do I attach a bat to the wheelhead?

What tools do I need for ceramics

What are suggested plate clay weights?

What do I need to get started?

What are observation holes ?

What tools do I need to make a coil pot

How do I fire ceramic bisque ?

How do I recycle batches of clay quickly

How do I care for my molds?

How do I fire my ware?

How do I roll a slab?

How do I fire my kiln?

What is the correct firing time?

How to I prepare and make slabs?

What is Leatherhard ?

What materials are toxic in Ceramics?

How do I fire glaze?

What are slabs?

What is Korean celadon?

How do I fire Raku?

How do I make paperclay?

Can Crackle glazes be used for food?

How do I avoid S cracks in wheel thrown ware

how do I apply glazes?

How do I get the press onside?

How do I open-up the clay?

How do I fire Reds/Yellows?

What is a glaze?

How do I fire Ceramic glaze ?

Can I repair my kiln?

What are the Approx. firing times?

Ho do I avoid pitting and pinholes?

How do I make throwing ribs?

What is Stoneware?

How do I care for my molds?

How do I apply kiln wash?

What is a Stain?

What is a mold?

How do I decorate my ceramics?

How do I remove mold lines?

How do I cut the spare?

What is a ´good teapot´?

How do I Bisque fire in an electric kiln?

How do I keep a kiln log?

How do I paint Eyes?

How do I decorate my ceramics?

How do I apply crackle glazes ?

What is Primary clay?

What are some easy projects?

What is Thermal Shock?

What effects can I achieve with a brush?

What are cones?

How do I Drain small pour holes?

What is Glaze?

What is Raku?

How do I remove a stuck lid?

How do I glaze my ware?

How do I make Egyptian Paste?

How do I apply texture?

What is overglaze/lustre?

Must my kiln be level?

How do I make my own brushes?

What clay should I use?

How do I apply a decal?

How do I clean my greenware?

What is Agate ware?

How do I care for my new Kiln?

How do I make stamps?

How do I load my kiln?

How long do I fire bisque?

How do I promote my work?

can I draw directly onto a piece?

How do I increase my profile?

How do I fire different bodies?

what is porcelain?

How do I make test tiles?

What is Earthenware?

What is the humming in my new kiln?

What should I remember when firing a new kiln?

How do I mend Greenware?

how do I get the best results in glazing?

How do I prevent dirt on my greenware?

How do I accomodate Clay Storage in my studio?

How do I fire Larger pieces ?

How do I prevent sagging during firing?

How do I brush one-strokes?

How do I load my brush for applying underglaze?

How do I mend molds?

Why should I use pottery plaster?

What is the coat coverage ?

How do I prevent glazes from settling ?

How do I fire lace figurines?

What is Albany slip?

How do I create a woodtone effect?

How do I light my Gas Kiln?

What is a pyrometer?

What is a Binder?

What is a glaze?

What are some Doing well Quotes?

What is Slip casting?

What is a Rib?

What is a Bisque?

How do I care for my elements?

How do I fire porcelain?

How do I store my throwing tools?

What is the History of tea?

What is the history of Ceramics?

Why do I get black spots in my glaze?

How do I fire flat pieces?

What is Terra-Sigillata?

What are Pyrometric Cones?

What is Iron Oxide?

How do I load my kiln for a glaze firing?





Not finding the advice and tips you need on this Ceramics Tip Site? Request a Tip Now!


Guru Spotlight
Byron White