Fumiya Mukoyama’s Zogan Yusai: Precise Pottery Decoration with Slip Inlay and Glaze Patterning


Inlaid geometric slip and glaze designs give Fuyima Mukoyama's pottery individual character.

Inlaid geometric slip and glaze designs give Fuyima Mukoyama’s pottery individual character.

For a young potter in a region of Japan where Mingei is king, coming up with a unique style can be challenging. But Fumiya Mukoyama did just that with his “Zogan Yusai” technique. Translated, “zogan” means inlaid and “yusai” means coloring with glazes. And as the name implies, Fumiya’s technique consists of slip inlay and colored glazed designs.


Today, Naomi Tsukamoto shares Fumiya’s technique step by step. In addition to the fabulous pottery decorating methods, I particularly liked Fuyima’s method for trimming on a chuck. – Jennifer Harnetty, editor.




figure 1.

Throwing & Trimming


Mukoyama uses several different tools and techniques to create multiple pieces of the same size, and to create a clean surface for his designs.


He throws the tea bowls off the hump, starting with a large lump of clay, centering it into a wide cone, then shaping, centering, opening, and throwing an appropriate-sized portion of the top section of this cone. As Mukoyama throws, he uses the curve on the wooden rib to determine the inside shape of the bowl.


Tip: When throwing off the hump, be sure to thoroughly compress the bottom interior of your vessel to prevent S cracks.


The tombo is a depth and diameter gauge. The one shown here (figure 1) consists of two pieces of wood joined perpendicularly, with a thin bamboo dowel cut to exactly the desired diameter of the bow that slides through a hole in he lower piece of wood. The piece inserted into the bowl is exactly the right height so that it touches the bottom of the bowl when the dowel marking the proper diameter rests on the rim of the bowl. Once you decide on a height, and cut the thin dowel to the desire diameter, you can create many pots of the same size.


Ready to go beyond dipping, pouring and brushing the same palette of glazes onto your work?
Turn to Surface Decoration: Finishing Techniques for ideas and inspiration!


figure 2.

After you finish throwing, cut the pot off the hump. Be careful to mark a line first so you don’t cut through the bottom. After the piece is leather hard, you’re ready to trim.


When trimming, use a chuck to keep the form well supported, prevent it from warping, and elevate it from the wheel head so that it can be trimmed all the way to the rim. If you don’t have a chuck already, throw a somewhat mushroom shaped solid form with a slight concavity and beveled top edges on a bat or on your wheel head like the one shown here (figure 2) and leave it attached. Once it is leather hard, it is ready to use.


Before trimming, use a surface gauge to determine the height of the foot (figure 3). This is especially necessary when throwing off the hump as the cuts made when removing each piece from the wheel may not result in a bottom with the same thickness each time.


figure 3.

Once the foot is trimmed to the proper height, the U-shaped gauge is used to determine the width of the foot (figure 4). The foot is then trimmed to this diameter. The next step is to trim the piece from the bottom all the way to the lip of the bowl. This removes excess clay and throwing lines and creates a smooth surface. In order for the inlaid design to come out clearly, it is important to make the surface as smooth as possible at this stage. Mukoyama ends the trimming by going over the surface with a sponge, erasing all the trimming lines. Finer clay works better for the zogan technique, and so a sponge works well. A rubber or metal rib would work if you are using coarser clay.



figure 4.

Drafting and Etching the Design


In order to determine where the circular patterns will be placed, Mukoyama draws drafting lines with calligraphy ink, dividing the surface into six sections (figure 5).The tools used to create geometric shapes do not have to be fancy. Here a medicine bottle cap is used for the circular pattern (figure 6). The lines on the cap help him to line up the circle vertically and horizontally with the lines drawn on his pot.


Clean and round the edges with a trimming tool after etching the design. After smoothing them, go over the lines with the needle tool to round inside of the lines.


figure 5.

A fabric rotary cutter (or a pizza cutter) is used to etch the dotted lines within the circles (figure 7).


Zogan (Slip Inlay)


Because the slip is only inlaid inside the lines, Mukoyama uses watered down pure Amakusa Porcelain Stone powder, which is equivalent to Cornwall Stone. This simplifies cleaning the surface later. This slip will not work for painting the surface though, because once dried, it is powdery and will flake off easily.


figure 6.

The slip should be quite watery, much thinner than the normal consistency, in order to fill in the small dots. Use the brush to lightly pat in the slip (figure 8). Once the slip dries, and becomes powdery, rub in the slip further using your fingertips (figure 9).


figures 5, 6, 7

Normally, you would scrape the surface in order to finish the slip inlay; however, since the slip was pure clay, all you need to do is to wipe off the surface lightly with a cheese cloth like fabric (figure 10). Be cautious not to wipe the surface too hard, otherwise, you will lose the inlaid lines. The more clearly you can maintain the division between the inlay and surrounding surface, the more vivid the final colors will be. After cleaning the surface, bisque fire the piece.



Glazing the Background


figures 8, 9, 10

Once bisque fired, make sure you clean the ware with a wet sponge first in order to achieve the best glazing result. Brush wax resist on the circular patterns. Mukoyama usually covers the lines with water-based latex resist using a very thin brush first, and then fills inside the design with melted wax mixed with kerosene using a small brush. Using latex on the lines ensures that the resist can be removed and reapplied if it is covering more than just the incised lines and patterned areas.


After the resist dries, glaze the inside by pouring first, then dip the base glaze outside. Wipe any glaze off of the circular design areas and clean any drips on the foot ring before the second bisque firing. The purpose of the second bisque firing is to burn off the resist and to fire on the base glaze.



figure 11

Yusai (Coloring Designs with Multiple Glazes)


After the second bisque, only mask off the lines (figure 11). You will want to fill in the rest of the area using colorants and glazes. Because some glazes do run, it works better if you mask a little over the lines rather than precisely covering only the lines.


Fill in each pattern with different glazes, metallic oxides, and/or underglazes. Mukoyama only uses two colors for each pattern to achieve a unified balance (figure 12).


figure 12.

You could also leave some parts bare to take advantage of the clay color. Glaze from lighter to darker colors as you work to keep them from contaminating one another.


This is the last glazing step. Think of glazes and stains as colors and carefully consider the color balance for each circular pattern and between the patterns. Also consider the type of finish (glossy, matte, and dry) you combine. Depending on how you combine the linear patterns and colors, you will find numerous design possibilities in zogan yusai.



Finished glazed and fired bowl, by Fuyima Mukoyama.

Naomi Tsukamoto received her MFA from the University of Colorado, Boulder. She currently teaches in Tokyo and works from her studio in Yokohama, Japan.


Fumiya Mukoyama graduated from Kyoto Prefectural Ceramics Training School in 1984, then studied under Shinbei Sakakura in Hagi. He now lives in Karasuyama-cho in the Mashiko region with his family.


For more great pottery decorating techniques, be sure to download your free copy of Ceramic Decorating Tool Techniques: How To Use Clay Pencils, Slip Trailers, Glaze Pens, and Carving Tools to Decorate Ceramics






  • Sherri T.

    I bet it’s a Japanese clay but Black Mountain clay is similar and is manufactured by Aardvark Clay, Cone 10. I believe that you can order from them online. They also have 2 retail stores: one in California and another in Nevada.
    I don’t think that Fuyima used the Raku method since a functional piece like this needs to be able to hold water, and raku pots’ porosity doesn’t allow that.

  • very good idea and beautiful advantage you had. a quality of fired body -I mean your black ware- that makes it more lovely and useful. thanx a lot for sharing.

  • Ben B.

    @Emily: I’m guessing that the piece is fired via some form of raku process–that’s the only time I’ve seen the clay turn that kind of black. (Yay carbon!)

  • Gigi .

    Love the double bisque firing, it really is a brilliant way to layer surface treatments without smudging delicate glazes & cuts down on multiple glaze firings!!

  • Emily P.

    I think this work is SO BEAUTIFUL! Is the final glaze a clear one over everything? What cone is it fired to? And why is the clay black in the end piece? Thanks for the inspiration!

  • Thank you, Naomi. This is one of the most complete observations on a high-end production process. Fumiya seemed to have perfected his craft for every step to a science.

  • Interesting article,I don’t do any production work or make exact duplicates of anything.I handbuild and wonder if some of these techniques would work with slabbuilding instead of wheel throwing??

  • Fires I mean, not firest. Fingers slipped…

  • Beautifull work. Does anybody know what kind of clay she uses. It looks like it firest to black matt which is really nice.

  • Here is an article about Tombo tool

  • Leonard C.

    Beautiful love the clean simple lines …but Why the double bisque firing

  • Neal O.

    It’s easy to make a tombo. You could use a popsicle stick and a chopstick. Throw a piece the size you want to make duplicates of. Lay the chopstick across the top. Hold the popsicle stick perpendicular, touching the bottom of the piece. Mark where it crosses the chopstick. Cut the chopstick to the diameter of the piece. Drill a hole in the popsicle stick and slide the chopstick through.

  • Tig D.

    Emily, you can make them yourself, using small flat pieces of wood and bamboo skewers. Of course, they are available commercially, but the satisfaction comes in making them and using them yourself. I used an old bamboo lawn rake, stripping the tines for main pieces, and a package of barbecue skewers. A bottle of white glue, and a small drill for holes complete the necessary fabrication tools.

    Make different ones for bowls, mugs, any repetitive shapes you produce.


    Tig Dupre
    in Port Orchard, WA

  • Emily J.

    Hi Naomi,

    Looks like the “Tombo” is a handy tool. Is it available here in America?


  • Stephen M.

    Mukoyama-san’s Chuck-making technique is similar to the one I was taught, except that rather than wait for it to get leather hard before use, we would de-water it with a sponge or soft rib, and then cover it with thin muslin to prevent the piece to be trimmed from sticking to it. This had the advantage that small adjustments to the shape of the chuck could be achieved very easily.
    I have on occasion used a proprietary brand of disposable dish cloth instead of muslin, which works just as well.

  • Wow, so much excellent information in a single post. Thank you!!

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