Robert Serb's Ceramics Notes

These are comments and thoughts I've had about the pieces I've made over the past 7 years, and about pottery in general. To see the gallery of pieces I've made, Go Here or click on "Ceramics Pieces" on the left.


I've revamped this site a bit, and broken it into four sections: current goals and projects, a basic pottery tutorial, a more advanced tips and tricks section and a bunch of notes and thoughts on specific pieces and techniques.

      So what were you interested in seeing?

(You can also just scroll down to see everything)


      Every semester I have a number of goals or techniques that I try to work on. Ideally, all my pieces will be uniformly thin, shapely, tall, with well-fitting lids and interesting sculptural twists, and all my glazing will be attractive with no thick "crackled" spots or thin, bare patches. All of those have been goals and things I've focused on at different times, and I continue to work on them. Each semester, though, I place a different emphasis on my work.

      Two events in the past 7 months have had a big impact on my pottery.
      The first was a trip to the Chicago Celtic Fest last September to see my nephewís Irish dance competition. Between sets I wandered around the Fest and spotted a booth selling interesting pottery. The Potter's name was Patty Rau, and I spent a while admiring her work and chatting with her about her techniques. The more I looked the more impressed I was; with a lot of skill she had carved celtic knotwork designs on her goblets, mugs and boxes and then fired them in different colors. Pattyís designs were very elaborate and neatly executed, and I was very impressed with her work.

      Here are a few photos I took of some of her pieces that I found particularly inspiring:

A jar with a knotted Celtic Design:
Celtic Model jar

A Goblet with carved Celtic knotwork:
Celtic Goblet 1

Another Cool Goblet:
Celtic Goblet 2

      Then over the holidays I went on my honeymoon to Ireland. While there we went on a whirlwind tour of the sites of Dublin and Galway, and saw many interesting Celtic decorations and designs. While I found the spray-painted sheep entertaining they weren't particularly inspirational. However, the floors, walls, furniture and even the gardens were covered with Celtic designs that interested and excited me:

The Floor of St. Patrick's Cathedral in Dublin:
Floor of St. Patrick's

Mantle Carving from the King's Head Pub in Galway:
(The carving's dated from 1612)
Mantle at King's Head

Celtic Cross with Spiral Designs near Galway:
Celtic Cross

At Dublin Castle Gardens
Even the Gardens and Walkways were inspiring!
Dublin Castle Gardens

Another Carved Celtic Cross
from St. Nicholas Church in Galway.
Another Carven Celtic Cross

Queen Victoria's Table in Dublin Castle
(My next woodworking project, maybe?)
Queen's Table

      It was a wonderful trip, and I came back with a couple of books detailing how to draw Celtic designs and a burning desire to try my hand at it.
      The first efforts were pretty bad; Iíd tried tying clay ribbons into the simplest types of infinity knots, but they would crack or fail to adhere to the body of the mugs I was attaching them to:

Early Celtic knot: Celtic Knot 14

Another of my early Celtic knots: Celtic Knot 15

      I slowly got the hang of tying the knots, then I began laying a cloth or paper pattern over the clay body, and carving the rough design, then adding more details as I attached the clay carving to the mug.

Celtic knot #10:
Celtic Knot 10

Celtic knot #12:
Celtic Knot 12

      Of course, I also ran into the never-ending problem of glazing. These two were supposed to be red, but even after 7 years red glazes still give me a lot of trouble.

Celtic knot #16:
Celtic Knot 16

Celtic knot #19:
Celtic Knot 19

      Sometimes as they heat up and liquefy the glazes will run, and they can obscure the design, like on these two:

Celtic knot #20:
Celtic Knot 20

Celtic knot #21:
Celtic Knot 21

      Lately, instead of attaching extra clay knots onto mugs Iíve started to throw thicker pieces (which seems like taking a step backwards) and carving the designs into the clay body itself. The results have been good so far:

Celtic knot #17:
Celtic Knot 17

Celtic knot #22:
Celtic Knot 22

Celtic knot #23:
Celtic Knot 23

      For the last month or so Iíve developed a new technique, based on some of the nice glazes that Iíve been using for the past few yearsÖ
      Iíve started carving celtic knots and other neat designs into the clay body, then drying and firing the pieces like usual. When itís time for the glazing and second firing, Iíve begun filling the grooves in the piece with a dark glaze, then sanding off the excess glaze until only the carved design shows, then dipping or spraying the entire piece with a clear glaze.
      The result: it looks as if Iíve drawn the design onto the piece (if it works outósometimes the piece cracks where Iíve carved it too deeply, or the clear glaze cakes up and becomes opaque, orÖ)
      Here are some examples of this technique:

Celtic knot #51:
Celtic Knot 51

Celtic knot #53:
Celtic Knot 23

Celtic knot #17:
Claddagh Cup #3

Celtic knot #55:
Celtic knot #55

Celtic knot #65:
Celtic Knot 65

      FYI: The numbers refer to the number of pictures I've taken, not the number of pieces I've made. I haven't made 65 Celtic knots yet...maybe 25?

      For these ones I tried using a white glaze to fill the design; I canít decide if Iím happy with the results or not...

Celtic knot #60:
Celtic knot #60

Celtic knot #67b:
Celtic Knot 67b

      Here's a link to Patty Rau's pottery site:
      Take a look, because she's got a lot of neat Celtic knots and other interesting designs!


      I've increased the height of my pieces to the point that I can consistently throw a vase or pitcher up to 14 or 15 inches high. That might not sound like a lot, but consider that my entire forearm, from extended fingertips to elbow, is only 20 inches. Working with one arm inside a piece and the other outside, fingertips pressing together as discussed in the "Advanced Tips and Tricks" section, that means a maximum height of 20 inches, unless I straighten my elbow on my inside arm. There are potters who can throw three foot vases and jugs by using their arm all the way up to their shoulder, but that'll be a goal for the distant future.
      The trick to that last business was the phrase "consistently". That means that the piece I throw should be uniformly thin all the way around, and from top to bottom. That doesn't really happen; when throwing a tall piece the bottom of the wall has to be thicker than the top, to support the weight of clay above it. The trick is to throw a piece, then let the clay dry and stiffen until it's leather hard, then go back and trim the lower part to the same thickness as the top. (clay that's leather hard can support weight better than soft, just-thrown clay, though it can still flex and crack, as I've unfortunately learned.) Thanks partly to better finger placement, partly to improved trimming techniques, and largely to lots of practice I've gotten better at making tall vases and pitchers, and making them thin enough so they don't actually weigh a ton, especially when filled with liquid. Still, I know there's room for improvement, and I'll keep working on it. (Go to the Ceramics Pieces section here or by clicking on the link at the left for a look at some of the vases and pitchers that I've made in the past year.)

      Lids are tough for a couple of reasons. They are usually thrown from a separate lump of clay than the body of the dish or jar that they will sit on. That means you have to carefully measure, using a calipers, to ensure that the lid is the same diameter as the pot. But that's just the start; clay shrinks as it dries, and sometimes a lid that seemed to fit perfectly when you made it will be too big or small when it and the pot have dried.
      Even if it's the right size in the course of drying the lid might warp or twist (which often happens with thinner or flatter pieces; see the "Advanced Tips and Tricks" section for a discussion of why) which means it won't sit properly on the pot. Or the pot might not dry uniformly, and instead of being circular be oval-shaped, or deformed enough that the lid doesn't fit well. Or....
      In any case, there are many reasons why lids might not fit. Some potters circumvent the problem by making several lids, each a slightly different size, that all match a given pot. When dry they choose whichever lid fits best, and toss the others into the clay reclaiming bucket. I've tried making a spare lid, especially for a piece that I've put a lot of work into, but usually resist that urge. I'd rather practice and get good enough that I can be reasonably sure that each lid will fit the pot it's intended for.
      By the way, lids have to be made at the same time as the pot, so that the lid and pot both dry--and shrink--at the same rate. It's theoretically possible to make a pot, let it dry, even have it bisque fired, and later try to make a lid to match it. But the pot will be dry, while the lid you're making will be wet clay, so you'll always be guessing how much the lid will shrink as it dries. You need to be really skilled and experienced to guess that and be right. Conversely, if both the pot and the lid are made at the same time from the same batch of clay, and presumably have the same moisture content, you can make them to match each other when both are wet, and as they dry they will (hopefully!) shrink at the same rate and still match when they are dry.
      Once the lid and pot are leather hard, you have to add a handle to the lid (sometimes to the pot, too). The potential problem here is that the handle might not adhere well to the lid, in which case it'll crack when fired. Or the lid might have dried nice and evenly so far, but when you add the weight of a handle it might deform as the drying continues. Or the lid might be nice and circular, but the lid wasn't quite centered when you attached the handle to it. Or...
      Peter and Lou have given me lots of advice and suggestions about lid shapes and techniques. Your pot might have a flange inside it below the rim, to hold the lid. Or the lid might have a flange inside to hold it on the pot. The lid might be a flat "hockey puck" (as Peter calls them) or might be an inverted bowl on it's own. Or it might be thrown as a double walled bowl, or...
      There are a thousand different possibilities, which means lids can be a lot of fun and showcase your creative well as being incredibly frustrating.

Here's a collage of some of the lids I've made in the past:
Lid collage

      For a better look at some of the lids I've been making go to the Ceramics Pieces section here or by clicking on the link at the left.

      In the past I've played around with bowl shapes, making a few square or triangular bowls, even a few swirled and fluted ones. But in 2007 I began really getting interested in the possible shapes for bowls. This was because someone in the studio put a poster up on the wall, right next to my favorite wheel, which showed a number of different types of bowls. There were fluted rims, scalloped rims, roped rims, swirled rims.... There were triangular sides, squared sides, inverted sides, grooved sides....
      I suppose it was a natural progression from the sculptural faces I'd been making, but I suddenly began making a lot of different shaped bowls.

Bowl collage

Here's a collage of some of the shaped bowls I've made. Right now I seem to be favoring the three-cornered ones, but that's because these are all individual soup-sized bowls. I'm sure I'll start shaping and sculpting larger bowls at some point, which might lead to 17-cornered ones. You can get a better look at these and some of my other bowls in the Ceramics Pieces Section.


      Over the longer term I hope to improve my ability to make identical pieces. It would be nice to be able to make a set of something, even just a set of two matching bowls or mugs. But that's really tough; even skilled potters have a difficult time throwing identically sized plates, bowls or mugs.
      You have to start by weighing the clay, and selecting identical lumps to throw. Because of differences in moisture content weighing clay is more likely to give you identically sized lumps to start with than measuring some other way--but even then, a two pound lump of really wet, water-laden clay might be much smaller than a two pound lump of dry, stiff clay.
      Then you wedge the lumps and throw them; but no matter how carefully you try to match them there are likely to be small differences in height or diamater between the pieces. Peter tells me that even experienced potters, if they're asked to make a set of 8 plates, for example, commonly make several extras, sometimes twice as many as requested. That's partly because pieces might crack or warp during the drying and firing, but mostly to insure that they can pick the most closely matched pieces to make up the finished set.
      The most common solution to making identical pieces is molding them. The sets of pottery you buy at Target were almost certainly made from a mold, which ensures that a bunch of identical pieces can be produced. Of course, making the mold itself is a time-consuming and cumbersome process, so it only makes sense if you're going to make dozens or hundreds of identical copies of a piece.
      The other solution, and the one I plan to tackle, is simply to practice.


      Lastly, somewhere down the road I hope to develop my skill enough to make intricately carved and sculpted scenes and designs.

My Dad's heirloom Stein Dad's Stein

The other side of My Dad's Stein Dad's Stein

My eventual goal is to be able to make pieces like my Dadís prize heirloom; a gallon beer stein that his great-grandfather brought from Germany long ago. Itís carved with scenes of German barbarians fighting the Roman legions, as well as trees, leaves and vines. Iíve always been fascinated by the intricate detail on it, and would love to be able to make such a beautiful piece someday.


      A well-made piece is uniformly thick; the bottom and sides are the same thickness and weight. Unfortunately, unless your piece is nearly vertical, or very small, you canít actually throw a piece with a uniform thickness; it will bulge or collapse from the weight above while itís drying.
      For example, an ideal bowl shape has sides and a bottom that are nearly the same thickness. However, if you actually throw wet clay into this shape the sides will collapse under the weight above them before the clay can dry and harden.
      One solution is to make bowls on a plaster mold, so theyíll retain their shape while the clay is drying. Many large bowls are made that way. However, you spend as much time making the mold as you do the bowl. Also, you canít really experiment with different sizes and forms when using a mold.
      The other option is to throw the shape with a thicker base, to support the weight above while itís drying. The thicker base means that the clay above has added support and wonít collapse. The downside is that the piece will be very heavy and clunky in appearance when itís finished. The solution: trim the excess clay off the base of the piece once itís leather-hard and stiff enough to hold itís shape even if the base is thin.
      To trim, once a piece is leather-hard you turn it upside-down, center it on a wheel, and hold it in place with either a grip tool or several balls of clay placed around the circumference of the piece. Then, using one of the trimming tools, you slowly rotate the wheel while shaving off thin ribbons of clay until the base of the piece is the same thickness as the walls.
      Here are a few photos from Brushy Creek Pottery showing a potter trimming a piece:

Trimming Clay 1 Trimming Clay 2

      There are a number of problems with trimming, and tricks to do it right. One common problem is that if a piece isnít perfectly centered while trimming you wonít be able to trim it evenly. Thatís even more of a problem if a piece isnít perfectly circular; pieces that are deliberately twisted or compressed out of shape canít be easily trimmed; they have to be trimmed by hand, a much more time-consuming and less precise process.
      Another problem is that, with the piece upside down, itís hard to judge exactly how thick it is and how much clay you should trim away. If you trim too much you can poke a hole right through the piece, or leave it so thin that it will crack during the firings. If you donít trim enough the piece will remain thick and heavy, and again could crack during the firings.
      Some potters carefully trim a bit, then turn the piece over to check how much clay remains, then trim a bit more. But since you have to carefully center and secure a piece to the wheel each time you check it, that can make the process even more time consuming.

      Over the summer I saw a demonstration by a Japanese Master potter named Art Tawata, who dazzled me with his ability to throw very large yet thin pieces. After the demo I spent a little time discussing his technique, and received two valuable tips.
      FIRST: the most difficult parts of a pot are the rim and the bottom.
      Master Tís advice was to concentrate on making those areas nicely formed, centered and thin, and the middle section of your piece would naturally conform to them. If your pot is 90% straight, but off center at the top or bottom, it will be obvious. But if the top and bottom of a piece are both centered and uniformly thin, itís almost impossible for the middle section to be warped or off-center.
      Since then Iíve put his advice to the test, and learned that I can, indeed, throw a pot with a warped or twisted middle section yet smooth and centered top and bottom. Peter, my ceramics instructor, praised those mistakes and called them ďartisticĒ.
      SECOND: use just your fingertips.
      To throw a piece the clay has to be covered with a thin layer of water, which allows the fingers to slide over the clay without much friction. If the clay becomes too dry the fingers will stick, and the clay will either tear or be twisted out of shape.
      To solve that problem many potters, including myself, keep dripping more water onto a piece as theyíre throwing it, to keep it wet. Iíd actually gotten into the habit of holding a soaked sponge in the palm of my hand as I threw, ready to drip more water onto the clay as soon as I felt it beginning to stick to my fingers. (This created a problem if I suddenly had to shift my finger position to shape the piece, while still holding the wet sponge in my palm.)
      Art Tawata pointed out that your skin absorbs moisture, so the more skin surface is in contact with the clay the quicker it will dry out. He threw with just four fingertips, pressing his index and ring fingers against each other with the clay in between, and rarely had to moisten his clay.
      Iíve been trying that technique and find it works well, in theoryóthe clay stays moist when you have less skin in contact with it. The drawback is that using just your fingertips makes it more difficult to judge how thin your clay is getting, or whether itís centered and smooth or off-center and lumpy.

Here's a photo of Master Potter Art Tawata throwing a pot, using just his fingertips:
Master T's fingertip technique

      Peter Hessemer has been helping me refine my throwing technique. In particular, heís been pointing out some problems with my finger placement and helping me overcome them.
      Throwing a piece, unless itís a very shallow bowl or dish, requires both hands (If itís a shallow dish you can throw it with the fingers of one hand on the inside and the thumb on the outside). Normally, you place your fingers directly opposite each other, one hand on the inside and one on the outside, and compress and draw up the clay. However, you donít actually want your inside and outside fingers to be parallel; that doesnít shape the pot, but simply draws it up as a straight cylinder.
      Having one set of fingers above the other defines the potís shape, as well as drawing it up and thinning the sides. Whichever fingers are lowest on the pot adds the shaping force and direction. If your inside fingers are below the outside fingers then they force the clay wall out, and the pot will flare and grow wider as you go up. If the inside fingers are above the outside fingers then the outside fingers force the pot in, and it narrows and forms a tighter neck as you go up. The trick is to know when to do which.
      Most intermediate potters will make one pull with their fingers in the same position, flaring the pot out or in depending on which fingers are lowest. Then they will go back for a second pull, starting halfway up or so, and reverse their fingers to flare the pot in the other direction. They may then go back for a third pull, reversing the second. With practice, this technique results in a multiple flared shape; bulging out, then in, then out againóthis is how many vases are formed.
      However, making three or four pulls to the clay thins it too much, especially at the top where itís pulled 3 or 4 times, while the bottom may remain thick. It also dries the piece out too quickly. And the more pulls you make the more likely the pot is to end up lopsided, thinner on one side than the other.
      The other option is to ďswitchĒ finger position halfway through a pull, raising the lower set of fingers above the upper set, while still applying even pressure to the clay to keep the walls uniformly thin. This requires a lot of practice, and Peterís been helping me with a lot of advice and suggestions as I work on that technique.

      Here are a few cutaway photos where I try to show the difference finger placement can make; click on the image for a larger size:

With your inner fingers above the outer ones:
The clay is forced inwards by
the lower fingers as you go up
Inner hand above

With your inner fingers below the outer ones:
the clay is forced outwards as you go up
Inner hand below

      Another problem Iíve been working on is compressing. When thrown, clay has a high water content, and as it dries the water evaporates and gaps or cracks in the clay appear. To combat that, the clay has to be compressed, making it denser, squeezing out some of the water and eliminating or reducing the gaps the evaporating water will leave behind.
      The action of throwing naturally squeezes the sides of a pot, compressing the clay. Itís very rare for the sides of a piece to crack while drying, unless theyíre either very thick or very thin. Thatís not true of two parts of a pot: the bottom and the rim. Most cracks occur there, because the clay hasnít been compressed as much by the throwing.
      To prevent cracks on the bottom the clay has to be compressed, either with the side of your hand, or a sponge, or a flat tool. The problem with this type of compression is two-fold; if you press harder in one spot than another, your bottom will be thinner at that point, and might break through, warp during the drying or crack in the firing. Also, if you use a sponge to compress the bottom the sponge will pick up fine particles of clay, leaving only the coarser elements. A number of my cups and pots have a rough, pebbled surface to the inside bottom, because I used a sponge to compress them.
      The solution to that is to use just your fingers, but I've found that tends to make the bottom uneven, leaving bumps and ridges where the gaps between my fingers were. Using the sponge tends to make for a smoother bottom. Instead I try to compress the bottom as quickly as possible, so fewer particles are removed by the sponge, while still compressing it as evenly as I can. I also pour an extra bit of glaze into the bottom of a piece, which will fill in the rough spotsóbut that can be tricky because if the glaze is too thick it will crack.
      Compressing the rim of a piece is more problematic. Simply squeezing the rim will make it thinner and taller, while the very edge will remain rough and is likely to crack. Some potters use their fingers to squeeze the rim of a piece inwards, while using a thumb on the top to press it downwards so the rim doesnít become too thin. Thatís VERY difficult, because applying pressure to the top of a piece can create bulges and make it lopsided lower down.
      One solution Iíve been trying is to use a small piece of chamois leather, soak it in water, and wrap it over the rim. Then I spin the wheel while pulling lightly on the edges of the leather; this condenses the rim edge without thinning it. Itís still possible that bulges will appear lower down, since the leather still pushes down on the top of the pot, but it seems to work better than just using your fingers, and the leather doesnít pick up clay particles as readily as a sponge does.

      Torque is the rotational force applied to a clay body by the turning wheel. Itís caused some problems for me in a number of ways.
      Normally the wheel spins clockwise, at a variable speed controlled by a foot pedal. As I center a lump of clay I spin the wheel rapidly, to eliminate any minor lumps and bumps in the clay and smooth it completely. Then as I begin to throw and pull up a piece I slowly decrease the speed, because the wider and taller a piece gets the more impact a minor push or jiggle of my fingers will have in shaping it. By the time I get to the top of a piece the wheel is turning very slowly.
      Problems come up if the clay is too dry; your fingers will stick to it and the clay will twist or tear. Iíve had several pieces that ended up lopsided or twisted because my fingers stuck. Some potters coat their hands with oil or Vaseline to keep from drying the clay out, but that creates other problems when the oil is absorbed by the clay; it increases the drying time of the piece and inhibits the ability of the dry clay to absorb glaze.
      The other problem arises while pieces are drying; during the throwing the clay is twisted by the torque, particularly near the top, and while itís drying the piece will slowly untwist. Peter demonstrated this to us by throwing a tall piece, then drawing a series of vertical lines on it and leaving it to dry. When the piece was dry the lines had twisted into a series of narrow ďSĒ shapes because the top of the piece had untwisted.
      If the pot is symmetrical this isnít noticeable. When it is most noticeable is if you are throwing an addition piece, such as a spout for a teapot or pitcher. The spout gets twisted, and while itís still wet it has to be attached to the side of the teapot. Then it will untwist while it dries, and you may come back to find a spout that looked straight when youíd attached it now looks twisted and warped. Iíve made several teapots with spouts that look like bent noodles because of this problem.
      There are a couple of fixes to this that Iím working on. One, used by expert potters, is to regularly reverse the wheelís motion, so the clay gets twisted both ways during the throwing. Hopefully, the torque applied when the wheel is spinning clockwise will balance the torque applied when itís going counter-clockwise, and the piece will dry straight.
      Iíve tried this, but found it too difficult; when the wheelís direction is reversed you have to reverse your hands and finger placement, something Iím not talented enough to do easily.
      The other fix is to try to estimate how much torque was applied to the spout, and attach it at an angle, so when itís untwisted it will look straight. This can be tough; thinner pieces twist, and untwist, more than thicker ones, and more torque is applied at the top of a piece than the bottom. Itís a guessing game that Iím still working on learning.
     The last option is to make spouts without using the wheel, by coiling or handbuilding. The problem I have with that is that I have big hands, so my handbuilt pieces tend to be thicker than thrown pieces. It doesn't look good to have a beautifully thrown, thin teapot with a thick, heavy spout attached.
      Hopefully, Iíll find a good, consistent fix to the torque problem soon.

      Working with clay means getting dirty. I once saw a documentary about pottery in which some famous English potter was throwing teacups while wearing a three piece suit and tieóand didnít get anything but his fingers dirty. Perhaps when Iíve been doing this for 30 years Iíll be a ďcleanĒ potter, but for now when I go to the studio I come home with clay spattered on my arms, chest, legs, hair, etc.
      If youíre squeamish or fastidious ceramics probably isnít for you.    ( FYI: kaolin, one of the main elements in clay, is also a stabilizing element used in a lot of foundation makeup. You may get dirty working with clay, but it wonít damage your skin...well, actually...most potters I know complain of two regular injuries; dry skin from working with clay, and cracked fingernails from the turning wheel.)
      Working with clay also requires WORK. Iíve come home some nights after just a few hours in the studio aching from head to foot. My shoulders ached from kneading clay, my arms ached from throwing it, my back ached from hunching over the wheel, and my legs ached from keeping the wheel turning. If you think of Demi Moore in the movie ďGhostĒ when you think of pottery, be aware that if sheíd really been a professional potter her arms and legs would have rivaled a linebackerís. (Yes, Iím aware that some potters look dainty or delicateóbut find out what they do. If they make tiny teacups or little soup bowls that doesnít require much strengthóbut a potter who regularly makes large pieces will get muscles doing it.)
      Working with clay also requires a lot of patience. Even in the best of circumstances the time lag between starting to make something and actually having a finished piece to show requires two weeks. Throw in all the frustrations and aggravations which come along: clay thatís not properly mixed, or too stiff, or too wet, or has air bubbles; pieces that crack while drying or firing; glaze that runs or globs or spits; and so on. This is not a hobby for those who canít deal with frustration and failure, or who require instant gratification.

Here are all the steps involved in making something from clay:

      The clay has to be mixed and kneaded, like bread. This evenly distributes the moisture throughout the clay and eliminates any air bubbles. Air bubbles are deadly in ceramics. Since pieces are fired to between 1200 and 2400 degrees, and since air expands when itís heated, even a tiny air bubble will expand to the size of a baseball and turn your pot into a bomb, complete with explosive shrapnel that will destroy other pots sitting next to the exploded one.
      Once the clay is kneaded you can use it to make something; some of the techniques include slab building, hand building, molding, pinching, coiling, slumping, slip casting, and throwing. Iíve done all of these, but really like to focus on throwing, which is what potters call it when you shape a lump of clay on a wheel.
      A lump of clay is stuck onto a turning wheel. While the wheel spins the clay is centered, which requires a lot of muscle, especially for a larger lump of clay. Then a hole is opened in the exact middle of the top of the lump of clay, then the sides are pulled up, creating a cylinder. The sides of the cylinder can be pushed or shaped into a variety of different forms, from vases and mugs to teapots and bowls.
      I like throwing because the action of squeezing the sides of the cylinder while pulling it up compresses the clay, making it stronger and denser and allowing me to make taller and thinner pieces than I can by coiling or slab building. The drawback is that you have to keep your hands wet while throwing, which adds moisture to the clay and increases itís drying time.
      Once a piece is shaped it has to dry to a ďleather-hardĒ state. This can take 1 to 5 days, depending on the initial dampness of the clay and the humidity of the drying area. Leather-hard clay is stiff enough to retain it's shape, while still being somewhat workable.
      Once itís leather-hard it can be trimmed, in which excess clay is removed from the bottom of the piece, or designs can be carved into the clay, or extra pieces of clay can be added, like handles on mugs or the spouts of teapots. This is a tricky process, because clay thatís added is a different consistency and dampness than the original piece, and sometimes the two donít bond well, which can lead to cracks in the final drying or firing. Many times Iíve added handles or decorations to a piece, to return later and find that the handle had cracked and fallen off, or the original piece had split or deformed due to the added weight.
      Now comes more dryingóall the moisture in a piece has to evaporate before it can be fired. This is because water, like air, expands when itís heated. A clay piece may seem dry on the outside, but if thereís still water in the middle and itís heated to 2000 degrees the water will expand and your pot will explode. Clay pieces have to be ďbone dryĒ before they can go through the first firing. At this stage clay pieces are extremely fragile and delicate; even a slight jar can cause them to shatter.
      Once the piece is bone dry it goes through the first, or ďbisqueĒ, firing. Pieces are loaded into a kiln and it is fired to between 1200 and 1600 degrees, over a period of 24 hours. This causes the clay particles to bond together, giving your piece strength and stability. Once pieces go through the first firing they are called ďbisque wareĒ. The first firing also causes pieces to shrink as the clay particles bond; depending on the chemical composition of the clay pieces can shrink between 5 and 15%. This is the primary reason for firing clay pieces twice; itís better to make your piece shrink before you glaze it and fire it again, because the glaze may shrink, or even expand, at a different rate than the underlying clay. Some studios glaze pieces when bone-dry and fire them only once, but unless the clay and the glaze have similar shrinkage rates the pot will crack.
      Bisque pieces are water repellant but not waterproof; they can be used as sculpture or decorations but not for cups, bowls, utensils, etc. Prolonged exposure to moisture will cause bisque ware to crack.
      Bisque pieces can be glazed, which involves dipping, spraying or brushing ceramic glazes on them. Glazes are formed from a number of different materials, but primarily flint, alumina, a flux material to help them melt, and different coloring or texturizing agents. Flint and alumina, when heated, create a glasslike material, which bonds with the clay to make a watertight surface. The glazed pieces are placed into a kiln and heated to 1800 to 2350 degrees, again over a period of 24 hours. This higher temperature can cause additional problems; a pot that was safely heated to 1600 degrees may crack when heated to 2350 degrees, and what looked like a tiny flaw in a bisque ware piece may turn into a yawning chasm in the second, hotter firing.
      Some of the different materials in glazes donít mix very well, or do so too readily. You might glaze half of a pot with a blue glaze and the other half red, only to discover later that the glazes melded into a dirty brown, or repelled each other, leaving a gap between them. Other glaze materials may work well at 1800 degrees but vaporize at 2300 degrees, which causes ďspittingĒ; glaze particles vaporize and explode off the pot, leaving a pockmarked surface behind.
      Also, glaze elements behave differently at different temperatures. A glaze that is bright red if fired to 2100 degrees may become dull red at 2200 degrees, or even green at 2300 degrees. I've had many problems with glazes; particularly red ones. Minor differences in the temperature of the firing, or the presence of too much or not enough Carbon Dioxide or Oxygen in the kiln during firing, can make a red glaze appear brown, green or gray. This is why some of the faces I've made in the "Ceramic Pieces" section look like they have blue or green lips; all I can do is keep experimenting until I find a glaze formula that works well.
      During the second firing a piece may shrink again, up to another 5%, and the glaze may shrink as well, or even expand, depending on the chemical elements in the glaze and the temperature involved. If the clay shrinks much more than the glaze does, the clay will crack. Conversely, if the glaze shrinks and the clay doesnít, the glaze will crack; resulting in a network of hair-fine fractures in the surface of the piece that is technically called ďcrazingĒ. Pieces that have crazing shouldnít be used to hold liquids, at least for any length of time, because the moisture will seep through the glassy layer into the underlying clay, eventually causing it to crack.
      Certain glaze elements are toxic; more commonly in their raw form than after being applied and fired. Ceramic artists usually wear gloves and masks when mixing glazes. Everyone knows that lead is toxic, and it used to be a common element in ceramic glazes; if you have an heirloom teapot itís probably got lead in it. Barium and Lithium are other glaze elements that are toxic in certain concentrations, but which produce deep, rich colors. Potters will experiment with a number of different glaze elements, depending on the clay theyíre using and the purpose of the piece. A barium or lithium glaze might be unsuitable for a bowl used for eating, but could be fine for a piece of sculpture.
      Working with glazes requires a lot of trial and error, and a lot of ruined pieces until you really understand how different clay bodies, glaze elements, and temperature settings work together.

      Lastly, a number of people have asked about the bottoms of pots, which usually arenít glazed. The reason is that when glaze melts, it may run, and if it runs to the bottom of the pot it can fuse with the kiln shelf the piece is sitting on. Those pieces which are glazed on the bottom, such as those you might buy commercially, are often unglazed in a very small ring at the bottom of the piece. The Potter who makes such pieces has found a glaze formula that doesnít run, and will glaze an entire piece, then rub the bottom on a damp sponge to remove the very lowest bits of glaze and keep it from sticking to the kiln shelf. The other way to glaze the bottom of a piece is to glaze it, then fire it on a ďstiltĒ; which is a series of iron wires that can withstand the high heat in a kiln, but which wonít bond with the glaze.

      The most important tools in working with clay are your own hands. Many potters use little else. On several occasions the Instructor has turned off the lights and made us throw clay in the dark, by feel. This is because your eyes can deceive you more than your hands, when handling a lump of clay. It may look centered but not be; while if it feels symmetrical it probably is, even if it doesnít look like it.
      There are a variety of specialized tools, or general tools that have been adapted, for use by potters. My own tool kit includes a bunch of different items, some of which are only useful for a very specific carving or decorating task.

My tool kit includes:
Potters Tools

The studio supplies the clay, glaze elements, potters wheels and kilns.

Some photos of me throwing clay:

Wedging Clay
Wedging Clay

Still Wedging Clay
Wedging Clay

Ready to Start
Ready to Start

Centering a lump of clay
Centering a lump of Clay

Throwing 1
Throwing 1

Throwing 2
Throwing 2

The most important tools
Most Important Tools

Throwing 3
Throwing 3

Throwing 4
Throwing 4

The Thrown Pot
The Thrown Pot

Cutting a cup off the wheel with the wire tool
Cutting loose a cup

Smoothing some rough spots on a bowl
that's dried to leather-hard
Smoothing rough spots

No matter how hard you work at it
problems come up: this bowl
cracked while it was drying
The Thrown Pot


I'm not fond of Raku, though it has it's advantages. The clay is much coarser than stoneware, with a lot of grit (small stone chips) and grog (old ground up bisqueware) added to help it withstand the shock of sudden temperature changes. Raku pieces are made and bisque fired in a regular kiln, then glazed with special glazes and heated rapidly to the melting point of glass, causing the glaze to fuse with the clay.

The problem I have with Raku is that pieces aren't waterproof or the glazes food safe, so you can't really make functional pieces with Raku. Still, as a sculptural medium Raku work can be much thicker than stoneware, and you can get much more vibrant colors from Raku glazes.

Oakton sponsors several Raku firings a semester, and I must admit they're neat to watch and fun to take part in. Here are some photos of a Raku firing:

Pieces being loaded into the Raku kiln
Loading the Raku kiln

The Raku kiln is fired
to between 1,000 and 1,200 degrees
for about 30-60 minutes
Raku Firing

The Raku kiln is opened and the pieces quickly removed;
they're covered with a trash can to stay in an airless environment while the glaze "cures"
Sometimes newspaper or other combustible material is added
which causes carbonization highlights in the glaze.
Raku Firing


      One of the neat techniques I've toyed with has been working with glass shards; several of the other artists have been doing that and I've finally gotten around to trying it. Beads of colored glass or shards and fragments from broken bottles are scattered on the bottom of a piece, or embedded in the sides, and as the piece is fired the glass melts and runs, spreading out and giving a cool, colored pattern. According to Peter there are a lot of dangers in doing this, ranging from bad reactions between chemical colorants in the glass and in your glazes to glass that cracks and leaves sharp edges as it cools. But I've just started to play with this technique; not sure if I'll continue with it yet.

      One trick Iíve been trying involves shaped vessels: last year when I made face cups I would throw a plain cup, then attach extra clay for the noses, lips, etc. The result might be a good face but the extra clay would make the cup heavy, and if the nose or lips made the piece too thick it would crack in the firing. This spring, on Peterís advice, Iíve been throwing thin mugs, then while theyíre still flexible Iíve been shaping the nose and facial features from the inside, pushing and molding the piece into the desired shape before carving the finer details of the face. The results have been face cups that might look similar to what I made last year, at least on this website, but are actually much thinner and lighter.
      Iíve also been making more sculptural pieces; most obviously with the ďfeetĒ bowls. This involves throwing a bowl with a very large ďfootĒ; the technical term for the ring of clay at the base of a bowl that holds it steady on a table. Then I would carve the foot until it actually looked like a pair of human feet (or, in one case, animal paws). Iíve also tried to shape some bowls into faces, but wasnít pleased with the results. ďIt looks like a rat,Ē Diane commented, so I added whiskers and tails and made several bowls that look like rats. Hey, Iím an English teacher, Iím allowed to be literal at timesÖ.

      Another new trick has been to try ďmixed clayĒ pieces. This involves wedging a lump of buff clay, another lump of red clay, and cutting, laminating and combining the lumps, then throwing a piece. The result, if itís done right, is a mug or bowl that has swirls of lighter and darker clay evident. Itís harder than you might think; the two clays have to be the same consistency and moisture content, or else when youíre throwing it the piece will fall apartóimagine trying to combine a thick, stiff jello with a thin yogurt and youíll get the idea. Also, joining the two clays can add extra air bubbles, which will become apparent when the piece shatters while being fired.
      One other drawback to this mixed clay technique is that, ideally, the different colored clays should be seen in the final product. Unfortunately, most of the glazes Iíve been using are completely opaque. To allow the swirls of different colored clays to be visible you have to use a semi-transparent glaze, but those are more likely to have problems. If the glaze is a bit thicker here than there, it will show up in a difference in the coloring. So far Iíve developed only one glaze, a greenish one called ďrhondaís celadonĒ that can showcase the different colored clays and yet fires to a consistent texture and color without cracking.

Red-buff mug 10 Here's a photo of one of my mixed clay mugs.

      I have tried to make a number of plates and platters and have had no luck; every one has either cracked or warped in the drying. In particular I wanted to make a ďswimming poolĒ complete with swimmers and divers sticking out of the water, and have tried 4 times to do that; each time the piece has either buckled or cracked. Thatís because flat pieces tend to dry unevenly, and the bigger the piece the more problems will crop up.
      When clay dries it shrinks, and the edges of a platter will dry first while the middle remains wet and heavy. In trying to shrink, the edges will either crack or bow upwards, warping the entire piece. Peterís advised me on some tips to try, such as weighing the piece down with pebbles to keep it from warping, or coating the edge with wax so it retains itís shape while the middle dries, but I havenít had time to try any of those yet. That might be a project for next semester.

Swimming pool 1
Here's a photo of one of my attempted swimming pools,
you can see that it cracked along the edge.

Swimming pool 2
Here's a photo of another swimming pool;
though a poor picture, you can see
how the tray bowed and warped while drying.

      I'll be adding more notes and photos about specific pieces and problems as things move along this year.

If any of this was confusing or unclear, then here are links to two online pottery tutorials that explain everything, with illustrations:

Lake Side Pottery Website

Professor Marvin Bartel's Learning to Throw Pottery website

You can also take a look at my Instructor, Peter Hessemer's, Website:
Peter Hessemer's Home Page