How to Make Agateware Vessels on the Pottery Wheel


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Agateware is a type of pottery that is made from a prepared mixture of various colored clays and mimics the variegated appearance of agate stone. It originated in the late seventeenth century in England, and is one of many great techniques for marbling clay. There are two types of agateware, one is wheel thrown and the other is made using handbuilding techniques, and is classified as laid agateware. Marbling pottery is also referred to using the Japanese words neriage and nerikomi.

In today’s post, Michelle Erickson and Robert Hunter explain the important considerations potters need to make when making agateware and demonstrate throwing agateware on the pottery wheel. – Jennifer Harnetty, editor.


A Simple Technique for Marbling Clay

by Michelle Erickson and Robert Hunter

Background on Agateware

The earliest English thrown agateware is found among the products of John Dwight (even though he himself referred to it as marbled clay). Considered by many as the father of English pottery, Dwight is well known in the annals of ceramic history for his innovations. He conducted numerous ceramic experiments beginning in the 1670s, delved into the mysteries of porcelain, and recorded his recipe to produce “marbled” stoneware pottery.

Dwight’s notes reveal two important material considerations in making an agate body: clay color and clay compatibility. To create the illusion of agate striations, different color clays must be obtained naturally or by modification, adding pigments or coloring agents. The tone of a natural clay can also be altered by sieving to remove impurities such as iron and sand.

Creating a successful variegated appearance also depends on the proportions of clay colors used. Clues for understanding problems related to combining multiple clays are also contained in Dwight’s formula. These include shrinkage rates, firing temperatures, density, plasticity, elasticity, and strength. All of these properties must be considered when mixing dissimilar clay bodies.


Beauty is more than skin deep!

Discover how you can create thrown and handbuilt pottery from colored clays where beautiful surfaces are part of the process. Curt Benzle demostrates classic colored clay techniques like nerikome, neriage, and colored slip decorating in his easy-to-follow step-by-step video Expanding Your Creative Palette with Colored Clay.

Check it out and view a clip


How to Make Marbled Clay Pots on the Wheel

To begin, clay slabs are built up, alternating the colors. This stack is then wedged or folded to form a ball that can then be thrown on the wheel.


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Care has to be taken during wedging to ensure the clays are mixed without overly distorting or blurring the resultant agate pattern. For demonstration purposes, the wedged ball is cut to show the pattern prior to throwing Care has to be taken during wedging to ensure the clays are mixed without overly distorting or blurring the resultant agate pattern. For demonstration purposes, the wedged ball is cut to show the pattern prior to throwing. The degree of success in an agate pattern comes from the initial wedging process as well as the throwing.


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During throwing, the surface of the clay body becomes smeared so that agate patterning is obscured. The prepared clay ball is then centered on the wheel. Once centered, the clay ball is opened and pulled quickly into a cylinder. During throwing, the surface of the clay body becomes smeared so that agate patterning is obscured.


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Care has to be exercised during throwing so as not to overwork the clay; otherwise, the pattern becomes muddled. This test piece was cut in half to show how the agate patterning shifts in the cross section of the clay wall. The different colors should remain distinct.


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Since nearly all Staffordshire thrown agate was subsequently trimmed on the lathe, the veining usually appears sharp and crisp. Later smearing and smudging can occur at the attachment points of handles or spouts as evidenced on some antiques. Most potters don’t have a lathe, but the pattern can be revealed by using a metal rib to scrape away the slip and outer layer of clay from the surface.


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Using a shaped rib or the metal rib again defines the foot or base while maintaining a crisp pattern.


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Lastly, scraping the interior of the form with a metal rib reveals the agate pattern on the inside.


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**First published in May 2013
Comments
  • Thank you for this post. I make agateware and was thrilled to see that this technique has been getting some focus. You can see an example of my thrown agateware on http://michellejunkinceramics.blogspot.com/ and you can see more pictures where I sell it on Etsy.
    Some things I learned along the way is to let the thrown agateware clay dry very, very slowly in the damp box. Testing on the clay bodies to find capatibility, as mentioned in other posts on this page, is key. Also when I make my clay balls for the wheel. I wedge the white clay separate from my black clay. Then I take a wire and cut each ball into 4 pieces; like a big apple slices. I take two black slices/pieces and two white slices/pieces and then assemble them together (slam them together) into a ball. Looking down at the completed ball, it has a distinct color pattern alternating 1 white slice, 1 black slice, 1 white slice, 1 black slice around the ball. Repeat process with other pieces…thus now you have two balls ready to throw. (Play around with how you assemble the balls, change up how many pieces of each color, you add. Try a ball that is half white, then half black.) When trimming a foot, make it wider than normal…so that cracking does not occur when the two clays dry or when fired. Also test and play around with glazing. I found that combinations of underglazes with my regular glazes help cover the dark clay or the white clay from showing through when I want complete color coverage.)

  • An excellent book about coloured clay is Paulus Berhenson’s “Finding One’s Way With Clay.” This should be a part of everyone’s clay library, whether you’re interested in agate ware or not.

  • Clay compatibility cannot be stressed enough when making agateware. There’s nothing like making a number of pieces using the process outlined above, trimmed and with handles applied, only to have them crack or flake apart during firing due to shrink rate differentiation.

    I also count my strokes during wedging in order to ensure consistency in marbling between pieces. Keep in mind, mixing occurs during centering and pulling, so you’ll want to go very easy on the wedging. That’s why it’s critical that care is taken to avoid trapped air when initially layering the clay. Marbling consistency between pieces is also affected by the rate at which each pot is pulled into cylinder. A quicker pull gives you a more dramatic effect.

  • I tend to wait til my “agateware” (I call it canyonware) is bone dry, then sand it with fine grit sandpaper. After that, I sometimes use files to grind grooves or designs into the pot before firing it.

  • Hey Dawn, I don’t see why you couldn’t make your own colored clays. Maybe you could have your students experiment with Mason Stains. I realize this might not fit your budget, but it might be worth a try.
    Add Mason Stains by weight as a percentage of dry ingredients when mixing your own clay. When coloring moist clay, allow for 30% water, then add Mason Stains as a percentage of dry ingredients’ weight (ie,
    17½ pounds dry out of 25lbs total weight).
    Greens, Blues & Blacks: 2 – 5%
    Yellows, Pinks & Purples: 5 – 10%
    (the above recipes on how to use Mason Stains was found at http://www.georgies.com/pdfs/mason-stains.pdf )

  • Cindy, similar to Michelle, I knead the clays separately, wire-wedge them together, albeit in layers, and then I finish with no more than 10 half-hearted kneads. It’s a bit of a balancing act; not enough kneading, and the clays can be prone to separating or cracking during firing. Too much kneading, and the piece will end up muddled. And as I mentioned before, you have to take into consideration mixing that occurs during the centering process. Working efficiently on the wheel is important. Take notes and have fun!

    Michelle, very nice work. I’ll try your apple-slice idea next time.

  • I’ve done this before with multiple colors….also you can wait till the clay is bone dry and use a brillo pad on it to ‘sand’ off the muddy color to reveal the marbled effect underneath…wear your mask! A good way to make this is to have a 5 gallon bucket to dump all your goopy chunky slip in from throwing from the different kinds of clay you use (keeping in mind similar firing temps/types of clay) mix it up a bit and then pour it on a plaster slab to dry out.

  • Can I just add my own oxides to the clay to create a white and … say irong oxide? I would think this would not change the shrinkage too terribly much since I start with the same basic clay body and I have done this with laid agateware. I am a teacher at a high school with a low budget and am curious to know if this is something worth trying with my more advanced students.

  • I have done some agate pots and used oxides with a white speckled stoneware and wedged it with the same stoneware. I also have used my dark and white clays together and got really good swirls when I carved into the clay.

  • I find the agateware contrasts more dramatically if I don’t use equal amounts of each color clay. Darker clays (Cassius and B3) tend to take over the marbleing so I like to use more Whitestone or Bmix. 3 clays that I have found success with are Whitestone, Speckled Buff and B3 brown. It is also important to have your clays at the same moisture content. Your fingers can get caught if there is a difference in moisture and texture and you end up having to trim off a misshapen piece. It is fun and the final effect, especially when glazed with a clear glaze, is really interesting.

  • Kevin, it would be nice to start experimenting where you left off. So about how many times do you wedge, and are you wire wedging or kneading?

    Thanks!

  • The most important thing about this process, and mixing any clay bodies where you want to maintain a distinct color separation, is to have the different clays at the same moisture level. This is best achieved by assembling your clay and letting it age for a week or so before you use it.

    Many thanks to Chris Campbell for teaching me the importance of this! Now to go practice this some more 🙂

  • We have been doing this for many years and the comments above are right on. We have used Cobolt Carb to get Just a touch of blue to the clays. To much blue and it looks tacky to me. Also a tip to not have the bottom crack is to put a small disk of your best non cracking clay ( mine is bcs10 by Clay ART) on the wheel first to become the bottom of the piece and then slam the mixed clays on to it. This has really helped. I usally just glaze part of the of the pot on the outside and brush oxcides and glaze over the first glaze to finish the pot I think you can find samples of this on our website if you look hard enough. http://www.birchgrovestudios.com The clays I use are Death Valley/ Black Mt./ BCS10 I get all my clay etc thru Clay Art in Tacoma Wa.

  • I found that glazing mixed clays was unsatisfying, as the darker clays often came out some ugly variation of grey green, even though the glaze was “clear.” However, I do like the finished appearance of a very thin application of straight Gerstly borate, or Colemanite. This gives a slight waxy gloss and brings out the color contrast. My work is fired to cone 10, with moderate reduction.

  • Laura
    To keep the clay from turning grey with clear glaze application, I have found that wetting the piece before dipping it in a clear glaze will keep the clay from absorbing enough glaze to grey it, but you still get an even application. Experiment to get the right effect.

  • i don’t wedge the two colors together at all. I wedge separately and then simply cut sections of each colored clay and stack them together. Sometimes I then cut the whole stacked ball or lump in half and reverse one half against the other for added interest. The less the clays are mixed on the wedging/prep table the larger the veining in the final product. I like using B-Mix 5 with Speckled Buff (both Laguna clays) and have had no problem with drying differences between these clays. I also buy some Amaco dry clay and use Mason stains (as someone else suggested) to create colored clays that I know are exactly the same clay body and have the same drying/shrinkage rates. I sand when bone dry but even then I get smudging sometimes. I also sand after bisque firing but have to use a power sander like a palm sander or a rotary sander with a fine grit paper. I haven’t broken a piece of bisque this way but one has to be careful. The tough part of agateware is getting the inside of the vessel trimmed without smudging. Trimming always seems to smudge the colors and while I can sand the outside, sanding inside is tougher. How do other folks get a really nice, crisp, smooth inside?

  • @Michael Grant: I have been successful on getting rid of the smudge by sanding the bisque fired piece with a drywall sandpaper. Make sure you put some gloves on to do that, as the first time I didn’t and my skin got really bad, so I learned it the hard way. 🙂

    @Dawn: You sure can mix your oxides to make your own colored clay, I’ve done that several times and it works pretty well. Just be careful to weigh your clay body, as the oxides are much stronger than stains you have to use really few, like never more than 5% of the clay, but usually less is better. I have done this mixing the oxides directly into the moist, straight out of the bag or reclaimed and wedged, ready for use clay. Have had no problems. I also think more of the white body in the makes for a better effect than equal amounts of white and colored. For more detailed info on this, refer to Susan Peterson’s book, it’s a very comprehensive volume and it covers everything about pottery from wedging the clay to glazing and firing your piece.

  • I have been working with colored clay, both hand-built and wheel-thrown for about 35 years, and still fascinated by the endless possibilities! You can mix oxides such as cobalt, chromium and iron into one clay body in addition to Mason and Cerdec stains. There are two books that are exclusively about colored clay: “Colour in Clay” by Jane Waller and “Coloring Clay” by Jo Connell that include many of the artists formulas (including mine).

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