Read these 92 Clay Bodies Tips tips to make your life smarter, better, faster and wiser. Each tip is approved by our Editors and created by expert writers so great we call them Gurus. LifeTips is the place to go when you need to know about Ceramics tips and hundreds of other topics.
Greenware mender: You can make your own mender. Lana Wilson, author of Ceramics: Shape and Surface, Handouts for Potters, uses this recipe called Magic Potion which she says is a super duper greenware fixer!!! The recipe is: I gallon water, 3 tablespoons liquid sodium silicate, 1 and 1/2 teaspoons of soda ash. *Liquid sodium silicate is also called egg keep and is sometimes available at drugstores.
Attaching dry parts. In general, you cannot attach two pieces of clay which have dried past the leather hard stage. However, there are some exceptions.
You can sometimes use a commercial mender such as Magic mender or APTII mender to attach pieces of greenware or even bisque.
Attaching wet parts: The first thing you learn in ceramics is "score and slip." To attach 2 wet pieces of clay, you score both sides with a needle tool or fork, apply water or slip, and mush them together. However, some potters, even famous ones, have abandoned the traditional score and slip method, saying they found direct contact to be more reliable. When using the direct contact method, it helps to have a binder. Vinegar works great for this, almost like a glue.
Paperclay is a wonderful material for making ceramic sculptures. It has improved qualities over normal clay. When fired the paper burns away, leaving a lightweight but strong ceramic structure behind. Here's How: Soak about 200 gms newspaper per kilo clay. Make some clay slip from your favorite earthenware or mid-fire clay. Mix the two with a ratio of about 1:4 parts paper pulp and clay slip with a drill mixer attachment. Pour the slop mixture onto a plaster bat or table for drying. When ready, wedge. Store in thick plastic bags. Tips: Shredded paper is ideal for making paperclay. Paperclay is suitable for handbuilding, not throwing. Mold in stored paperclay will improve its workability.
At some point you will decide to use low fire or high fire techniques, or like me, to combine them. Often it will depend on where you got started and what they used. Most popular ceramics studios low fire, and most colleges high fire. Low fire is usually cone 06-04 whereas High Fire (or some call Mid to High Fire) is cone 5-10. The difference between them is the temperature at which the clay matures “fuses” and glazes “melt”. Read my entire articleLow Fire or High Fire Clay
It is possible to decorate porcelain bisque with underglazes and one-strokes. This has to be done at a soft bisque(018) since porcelain fired to maturity would not absorb the colour. Some of these colours change when high-fired so it is best to run tests on colours
Favourite ways to let the clay dry out.
Some people spread it on plaster beds. Others in a large cardboard box lined with a garbage bag. My favourite is to put it into a pillow case or the sewn up legs of an old pair of jeans, hang from a tree, and let the water drip out.
The best advice of all is to do this often, before you have accumulated so much clay you can't bear the thought of recycling it all! And lastly, to keep clay moist longer in the first place, many potters store their bagged clay in an old refrigerator with the holes plugged. The tight seals help keep the clay from drying out.
Wrapping: A final technique for encouraging good attachment of wet and dry clay is to wrap wet newspaper around the completed object, then wrap in plastic. This causes the moisture levels throughout the piece to even out, resulting in less cracking. Great for those darned feet that keep falling off that too dry pot.
clay is too far gone to do: #1. Let it dry completely, then smash it with a hammer inside the bag, turning it into fine chunks. Drop it into a bucket of water. When you've accumulated a few gallons of watery slip, mix it up with a Clay Mixer (such as a Jiffy Mixer). Two additional things that improve the working qualities of the recycled clay: adding a small amount of vinegar to the mix, and letting the mix age for a few weeks. Finish by letting the clay dry until you can wedge it.
The following is a minimally dusty method to recycle clay trimmings and other clay scrap. (This does not mean that you can skimp on safety devices, put that mask back on!) While your clay scrap is still moist, roll it into thumb thickness coils and place it on a tray to dry. Remove the tray from your studio area (like a garage), or place it in an area that has very little air movement. The key is not to create an exposure to the finest clay dusts - they are the ones most readily moved into room air and these dusts are the most hazardous to your lungs. Read On: Clay Recycling D.I.Y. = The Cheap Method
Stoneware clays are fired up to 2370o F (1300o C), where they become quite hard and vitreous. Colors range from off white to gray and dark brown. There are also various degrees of roughness or fineness, depending on the formulation. This the hardest, most durable type of clay.
Hardpaste porcelain is characterized by its hardness, ringing sound when struck translucence, and shining finish, like that of a cowrie shell (Italian porcellana). It is made of kaolin and petuntse (fusible feldspar consisting chiefly of silicates reduced to a fine white powder); it is high-fired at 1,400ºC/2,552ºF.
One reason we wedge clay is to compress it or to align
and press the particles tighter together . If clay is not compressed properly, it can easily pull apart while you are trying to work with it. For example, have you ever had this problem? While you are pulling up a cylinder, the top ring of clay tears and comes off. Assuming you're using good clay and your pulls are consistent, this happens because the rim isn't compressed.
Mid-fire clays are a type of hybrid earthenware/stoneware clay that matures in between the two temperature ranges. This means that it is possible to get the qualities of the higher fired stoneware, while saving money and fuel in the firing. Mid-fire clays typically mature around 2100o F (1150o C) - 2265o F (1240o C)
1. The soft clay will actually harden on the underside faster than the top, because the plaster is soaking up the moisture.
2. Keep an eye on what sorts of clay are going into the mix, as this will influence the firing temperature.
3. This is also a good time to make paperclay!
Secondary clays can be broken down into: Ball Clay -- has some iron content; high content of organic matter (carbon); is more plastic; high shrinkage rate; melts around 2300o F (1260o C) Bentonite -- highly plastic; high volcanic ash content; good binding qualities Fire Clay -- has some iron content; melts around 2800o F (1400o C); varying organic content and plasticity Earthenware -- high iron and mineral content; naturally plastic; maturing range between 1700o F (926o C) - 2100o F (1150o C); Stoneware -- maturing range between 2,200o F (1205o C) - 2300o F (1260o C)
It is not just a matter of adding paper pulp to clay. There are some questions to be considered: what type of paper is best? (in my experience newspaper is actually quite good); how much should be added? (this question must be answered through experimentation, but up to 50 % is feasible). You can easily make paperclay yourself by mixing paper pulp with clay slip and then drying it out or by wedging in the pulp with the clay body. One can also purchase ready-made paperclay in some craft shops. There is even a product on the market called Creative Paperclay which doesn't need to be fired, but this is perhaps really moving too much away from the traditions of ceramic art. Still it is a new and different technique that could be checked out. Ceramics Today
1. Dry out all your old clay and keep it in a bag for recycling until you are ready.
2. Tip all the dried clay into a bucket and fill up to the top level with water. (Wear a dust mask).
3. Let soak for a few hours (best overnight).
4. The clay should have a soft consistency - slushy that is! Add more water if necessary.
5. If available, mix the soft clay with a drill mixer attachment. (Sometimes available in hardware stores).
6. Tip out the soft clay onto a large plaster bat for drying out.
7. When the bottom half has dried a bit, turn over.
8. When the clay has the right overall consistency, cut up into small chunks and wedge.
9. To homogenize the clay more, cut up and intermix different chunks and wedge again.
Prepare your clay properly.
Whether you are hand building or throwing a pot, you will have better success and much more fun when you adequately prepare your clay. Wedging is a technique used to prepare clay through kneading the clay then cutting it in half to check for consistency and air pockets. When no air bubbles remain in a cross section of clay you may begin. A good guideline may be about 50 kneading motions per 6-8 pound lump of clay.
Clay recycling: Dry the scrap clay on the bisque kiln or in kiln room (this loosens clay particle bonds--critical step). Slake (wet) it by pouring water over scraps in 5 gallon bucket. Let it sit for a while, then poke with stick to mix and debubble it. Pour off excess water into another bucket. Leave in kiln room till dry enough to spread on boards. Wedge when workable, store when proper consistency.
Recently I heard from someone who liked the feel of throwing a white stoneware however the specific application was using a glaze called 'butter' which comes out a beautiful creamy white to light brown. It looks better on a clay body which contains some iron as it produces iron spots and helps bring out the brown color. White stoneware has less iron and impurities than stoneware so to get the butter glaze to come out in a white stoneware our experts suggested to try mixing iron oxide into the clay we were preparing for the day beginning with a small quantity such as 1 teaspoon. Iron will help to bring out variations and brown spots in the glaze.
Cotton lace is the only kind of lace that will work effectively for porcelain draping. In the technique of porcelain lace draping, a piece of cotton lace is saturated with porcelain slip and added to a doll. When the piece is fired the cotton lace burns out leaving a fine shell of porcelain athat was in the originally saturated lace.
It's not totally dry, but too stiff to work with. Use the end of a
broomstick, a wooden spoon, or even a large screwdriver to poke holes in the clay, almost all the way through (leave about an inch at the bottom.) Fill the holes with water. Come back in a day or two and wedge the clay up. It will have absorbed the water and be nice and moist! An alternative method is to cut the clay into slices, soak them in water, then wedge. Or, take a soaking wet towel and wrap the clay with it. Place the whole thing inside the plastic bag. A couple days later, voila! Remember it is important to wedge clay especially when it has been rehydrated, to even out the moist and dry spots. Otherwise you will have difficult throwing, and pieces might warp as they dry.
It is rare that a clay as dug from the ground will suit our needs for forming. Typically we alter the clay by mixing it with other clays, silica, feldspar and grog or sand. We call the resulting mixture a clay body. Another clay might be added to increase the plasticity of a less plastic clay or to alter its color and texture. Silica, is added to control shrinkage and to increase the thermal expansion of the body to help make glazes "fit" the body. Feldspar or other fluxes are added to decrease the temperature at which the body will fuse (vitrify) to become water tight. Grog is added to control shrinkage and cracking as the clay dries.
Ceramics in domestic and ornamental use including earthenware, stoneware, and bone china (or softpaste porcelain). Made of 5% bone ash and china clay, bone china was first made in the West in imitation of Chinese porcelain. The standard British bone china was developed about 1800, with a body of clay mixed with ox bones; a harder version, called parian, was developed in the 19th century and was used for figurine ornaments.Porcelain first evolved from stoneware in China, about the 6th century AD. A formula for making porcelain was developed in the 18th century in Germany, also in France, Italy, and Britain. It was first produced in the US in the early 19th century.
Hand Mixing from Scratch
Hand mixing from scratch follows the reclaiming process fairly closely but you start with already dry powdered constituent materials. The trick is getting the dry powder materials blended without raising a lot of dust. I have seen dry clay blended outside in a kiln yard using hoes, rakes and other farm implements. This is messy and of course a respiratory hazard. (Anyone recognize a theme here?) Dry materials can be sealed in a large bag and massaged about in an effort to blend the materials, but you will be limited by how much clay you're physically capable of wrestling with! If you have a ball mill, the dry materials can be loaded into a large container, sealed and placed on the mill to turn...
After selecting a clay, you must wedge (knead) it to remove air bubbles and insure uniform consistency. A clay body that has been mixed properly and extruded from a de-airing pug mill is homogeneous, and because a vacuum removes most of the air, it does not usually need as much wedging for its first use. There are two common kinds of wedging, the cut wedging method associated with potters in the Western world and the spiral wedging method associated with potters in the Eastern world. The spiral method is more efficient, particularly when wedging a large chunk of clay, but the spiral method does take longer to learn. Cut wedging is only successful when the clay is very soft, so it is only recommended if you are mixing a very wet and a very dry chunk of clay for later use.
Most clay bodies that you will come into contact with are secondary clays that have been adjusted, or completely formulated clay bodies. In the formulated clays, the natural ingredients such as kaolins, ball clays, bentonites and other ingredients are mixed up to create a clay body of a particular type, e.g. a white earthenware. You can make your own clay bodies according to available recipes, experiment with your own variations or just buy a commercially manufactured clay from a potters supply shop.
Joining with paper clay: Paper Clay is a mixture of clay and paper fibers. Using it you can attach wet and dry pieces, and they will not crack. There are several excellent books on Paper Clay. You can make it yourself by wedging blended paper pulp into clay, or buy it in 25kg pugged bags. Paper Clay is excellent for handbuilding because of this ability to combine wet and dry pieces.
Bright candy colors, lightness, low-fire, These are a few things that describe white earthenware clay. Cast items are most often made from this type of clay. When an earthenware piece is struck with an object it often makes a “clanky” ring, while stoneware and porcelains are more likely to make a bell-like chime. Earthenware clays normally rely on talc (magnesia) as an active flux (melter), and ball clay as a source of silica, alumina and plasticity. The end result is a clay mixture that fires bright white between cone 06 and cone 2. Above cone 2, many earthenware bodies will begin to melt and slump and liquefy above cone 6!
The spiral wedging method has three main steps: 1. Push a cone of clay away from your body on a horizontal surface with the heels of your hands (the left hand does most of the work). 2. A thick slab of clay is created by this pressure. Partially roll this slab of clay back onto the cone with a twisting motion of your hands. 3. Repeat the process. With each pushing motion, the tip and lower surface of the cone are partially squeezed off, leaving the form with less mass. When the rolling action takes place, new mass is added to the form.
Picture a cross-section of clay with large particles of grog added. First, the grog opens the body to enable the clay to dry more evenly. As a piece of clay dries, the water on the surface evaporates. Water from the interior of the clay then migrates to the drier surface and, in turn, evaporates. Adding grog aids in this process by creating pathways for water vapor to move from the interior to the surface. Grog also helps control shrinkage. As the clay shrinks, the pieces of grog move closer together. When the pieces of grog come in contact with each other, the shrinkage stops. Adding too much grog to a body can make it very stiff and non-plastic.
Fast "souring" of reclaimed clay can be achieved by adding about a cup of organic cider vinegar to each 50kgs during the "accumulation" stage. Wedge thoroughly, then leave well wrapped in plastic for a week or three. The longer you leave it the better, but at least this way you don't have to leave it for a year before you use it!
Primary Clays Primary clays are clays that are found in the same spot as the parent rock (various types of granite), from which the clay originated. This means that the clay hasn't been moved by water, glaciers or other forces of nature. Most primary clays can be classified as kaolins. Kaolin is fairly non-plastic (difficult to shape) so it is never used on its own. It is also highly refractory, which means that it doesn't melt or fuse until a high temperature range, notably around 3,200o F (1760o C). Because kaolin is white, is usually used in white clays, such as porcelain.
This is the most common type of clay. Terra-cotta is one type of earthenware that is relatively coarse and red in color. Other earthenware bodies may be finer and have various colors, ranging from white to gray, buff and red. Earthenware clays are usually fired between 1700o F (927o C) - 2100o F (1150o C). At this temperature the clay body is still porous and needs to be glazed, e.g. if it is to be used as dinnerware.
Under-wedged clay is hard to throw because it is not
‘warmed up' properly and you could ‘pull a muscle'so to
speak. Also, it's problematic because it allows air bubbles to remain in the clay. For example, have you ever had a nice cylinder pulled up high and you find an air bubble in the bottom, this indicates you have under-wedged. Try to pop the bubble with your penknife tool then smooth it over with a few pulls. This may not work and you will have to start over. If you find the air bubble near the lip, cut it off just below the bubble and proceed with some nice pulls. For best results and more enjoyment, take the time to properly prepare your clay - especially for throwing pots.
The clay body selected for throwing is as important as the type of wheel and wheel head used. There are three general groups of clay bodies - red or white earthenware, stoneware, and porcelain. Stoneware usually has the best working properties. Because it is not always as workable as an earthenware body, porcelain is generally considered a poor clay to use when learning to throw.
When you begin working with ceramics it becomes quickly evident that clay is at the center of everything. Not only the quality of your clay bodies but how you store your clay, how you prepare your clay for throwing and the different kinds of clay available for different ceramics projects. Learn what to avoid with our clay body tips at ceramics.lifetips.com.
Clay bodies are usually suited to certain types of work. A smooth clay which works very well on the potter's wheel may have cracking problems when we try to handbuild with it. Large sculptures are usually built with very stiff coarse clay which would be unuseable for most other purposes. The temperature to which we'll be firing our work and the fired color and texture we desire will also dictate what kind of clay body we choose to work with.
Oven and Microwave Safety
Glazed earthenware is not normally recommended as an oven-safe material, however, it may be used in the microwave safely. There have been instances of earthenware pieces cracking in microwaves when a small food item has been placed on a large platter. In these instances, a large differential of temperature between the area that is in contact with food and the rest of the platter can be great enough to cause a fracture.
Porcelain is a totally manufactured clay. While it is not synthetic as such, various natural ingredients are refined and mixed up according to formulas. A good porcelain must be very white, vitreous, translucent while at the same time being plastic enough to work with. Porcelain is fired from 2335o F (1280o C) to 2550o F (1400o C).
Artists often choose white earthenware clay because the color palette associated with the temperature range is very broad. It is fairly easy to identify earthenware pieces in a gallery, they often announce themselves with loud colors! Decorating white earthenware is a little like working on a white canvas; when used in conjunction with modern underglazes and glazes, the artist is presented a “what you see is what you get” design situation. White earthenware is sometimes described as “short” or non-plastic because of the high percentage of non-clay materials. But it needn't be that way. Minnesota Clay's white earthenware is well-suited for throwing and handbuilding techniques.
A Pugmill is a machine for mixing and compressing a plastic clay. It mechanizes the handwork of wedging and kneading. Knives rotate on a central shaft and force the clay through a tapering barrel and out through a compressing nozzle. Pugging achieves some mixing of clay consistency but is more important for its effect upon compression and de-airing. Compression improves the strength and thus workability of a clay.
The world of clay bodies is vast, you can use anything from clay found in the ground to clay purchased in bags. Clay can have many different attributes and will provide many different experiences depending upon the needs of the potter or ceramists. Many people begin their clay experience with terra cotta (red clay) or earthenware clay and then move on to stoneware then graduate to porcelain also hopefully raku clay. Different pre-blended specialty clay bodies are available at retail stores, check with your local pottery and ceramics supplier to see what suits your needs.
Clay is basically a mixture of rock powder, that has been broken down by nature over millions of years, and water. There are various types of clay. These can be examined from two main perspectives: the geological origins of the clay ie: Primary and Secondary, and the type of clay body.
In the search for new techniques, paperclay is possibly an 'insiders' tip. Just what is paperclay? Paperclay is a mixture of clay and paper pulp.This mixture has many improved qualities over normal clay: it is lighter, as the paper burns away; it is very strong, both in the green state and after firing, due to the fiberous structure of the changed clay particles; it does not crack very easily, even when adding fresh clay to green ware, or even to bisqued ware, waste paper can be utilised for the purpose.
When moist, clay can be smooth, sticky or slippery, soft, and dense. Its shape can be changed without breaking the material--it can be modeled. We call this most important property of clay plasticity*. A sample of dirt we might find that becomes plastic when we wet it can be considered to be clay or to contain a large percentage of clay. When it is dry, clay can be hard, powdery, and fragile. When fired it is transformed to become very hard, strong, dense, brittle, and impervious to water. Read my full article: Physical properties of clay.
Very hard, opaque, water-resistant pottery made of non-porous clay with feldspar and a high silica content, fired to the point of vitrification (1,200-1,280º C) Glazing decorates and gives it a smooth finish; it usually fires to shades of gray or buff, though some red stonewares do exist. The earliest examples are Chinese, from the 10th to 3rd centuries BC. From the 9th century AD stoneware was made in N Europe; in Britain from the late 17th century.
Cut wedging: Cut wedging has two steps: 1. Cut a chunk of clay in half with a wire that is attached diagonally between a horizontal and a vertical surface. 2. Slap half of the clay, cut face down on the horizontal surface. Throw the other half of clay, cut face up on top of the first half. Repeat this step until the lumps, soft spots, and air pockets are removed from the clay.
|Jennifer Mathes, Ph.D.|