Make Gemstone-Like Polymer Clay Mokume Gane Cabochons for Jewelry
A 20th-Century Interpretation of a 17th-Century Decorative Metal Working Technique
Polymer clay mokume gane, or more accurately, polymer clay mokume is an extremely popular polymer clay technique that creates elegant and sophisticated patterns yet is surprisingly easy to do. It is an adaptation of mokume gane, a very beautiful and difficult 17th-century Japanese decorative metal working technique. The authentic technique can be done only by extremely skilled metal artists who have had many years of experience learning and perfecting this complex art form.
Fortunately, the polymer clay mokume technique inspired by this ancient form of decorative metalworking is easy enough that even someone who has only beginner clay skills can achieve extraordinary, unique, patterned veneers even on the first try.
Adapting the Metal Technique to Polymer Clay: Nan Roche, Tory Hughes, Lindly Haunani, Celie Fago and Julie Picarello
Nan Roche's 1991 book, "The New Clay: Techniques and Approaches to Jewelry Making", was the first introduction to her innovative adaptation of the traditional mokume gane technique for use with polymer clay. In subsequent years, many other top polymer artists (particularly Tory Hughes, Lindly Haunani, Celie Fago, and Julie Picarello) created and shared their own distinctive variations.
Polymer Clay vs. Traditional Mixed-Metal Mokume Gane
In the traditional metal working technique, contrasting color metal sheets are layered and then compressed to laminate them permanently into a solid metal billet. Then the billet is distorted by drilling holes, carving, forging, etc., which also exposes the distinctive patterns as different portions of the layers are exposed on the surface of the metal billet.
In the polymer clay interpretation, contrasting color sheets are layered and then compressed to laminate them permanently into a solid clay billet. Then the billet is distorted in one of many possible ways, which can include impressing it with a deep relief texture sheet or stamp or poking holes through the layers with skewers, pen caps, screwdrivers, blades, shape cutters, etc. If holes are poked through the layers, they may be left open or plugged with polymer clay.
If desired, the areas in between the holes (plugged or not) may be pressed down to create hills and valleys, further distorting the layers. The billet is compressed again and very thin slices are shaved off to reveal the patterned cross-sections of the stack, each new slice revealing a slightly different pattern as different parts of different layers are exposed. These paper-thin slices are applied in an overlapping pattern (collage) to a solid color polymer clay base as a decorative veneer before curing in an oven.
Favorite Polymer Clay Techniques
Mokume gane is my favorite polymer clay technique. What's yours?
New to Polymer Clay? Watch This Helpful Video on Basic Techniques
If this is your first time working with polymer clay, it's important to understand the basic techniques for conditioning polymer clay (by hand and/or with a dedicated pasta machine used exclusively for polymer clay), how to mix custom colors from two or more commercial clay colors, choosing a suitable work surface, rolling out the clay, and how to clean a pasta machine dedicated to polymer clay.
This short video, "Sculpey Polymer Clay - Getting Started", will give you a quick overview of these basic techniques. It was produced by the folks at Polyform (the manufacturer of Premo and Sculpey brands) and focuses on Sculpey, but applies equally to any brand.
Polymer Clay Mokume Gane Cabochons Step-by-Step Tutorial
Note: You can click on any of the following steps to jump directly to that section of the tutorial, if you wish.
- Condition, roll out, and trim the polymer clay sheets.
- Apply silver, copper, or gold leaf (optional).
- Stack and compress the polymer clay layers.
- Halve, stack, and compress the layers again.
- Make a reusable pad or base for the mokume stack (optional).
- Distort the layers in the mokume gane stack.
- Shave very thin slices from the top of the stack.
- Apply overlapping slices to a polymer clay backing sheet as a veneer.
- Cover the veneer topped backing sheet with plastic wrap and cut out the cabochons.
- Cure the polymer clay cabochons in a preheated oven.
- Wet sand the cured cabochons.
- Buff, seal or glaze the polymer clay as desired.
STEP 1: Condition, Roll Out, and Trim the Polymer Clay Sheets
Choose three to six colors of polymer clay that will complement one another but also contrast well.
You can use polymer clay colors straight out of the package, if you wish, but I prefer to blend several colors of clay into my own custom shades so that my mokume gane veneers don't look like anyone else's. Using opaque clay colors will produce a very different effect than using pieces of translucent clay that have been lightly tinted with small amounts of opaque colors. You also can use metallic or pearl clay, either by itself or blended with opaque or translucent clay colors for even more custom color variations. (You need only a tiny pinch of opaque clay to tint the translucent clay.)
Condition and roll out approximately 0.5 oz of each color or color blend you wish to use (1/4 of a 2 oz. block or 1/2 of a 1 oz. bar). Always condition the lightest color (or translucent, then white, then your lightest color, if you are using translucent and/or white) first and then move to the next-lightest color, ending with the darkest color of clay you are using.
To condition the polymer clay by hand:
Squeeze the clay in your fist as hard as you can, which will elongate it a bit. Then hold it horizontally between your palms and compress the ends toward the center. Repeat several times until the clay starts to soften and get warmer. Then roll it firmly between your palms into a ball and then a snake. Fold the snake in half and twist it as shown in the photo, and then roll it back into a ball and repeat until the clay is warm, smooth, flexible and supple has a slight sheen.
I recommend that you condition no more than 1/2 oz. of polymer clay at a time by hand. If you need to condition a larger amount, condition several smaller amounts, compress them together, and repeat the conditioning motions a few times until everything is homogeneous. Roll the conditioned clay into a ball and then flatten and compress it between your hands into a thick, squarish patty.
Use a baby wipe (or a paper towel moistened with some inexpensive hand lotion) to clean the clay off your hands, then fold the baby wipe or lotion-infused paper towel sheet into a pad and draw each side of your blade across it to wipe off the clay residue. If you used hand lotion rather than a baby wipe, wipe off the excess lotion from your hands and blade with a dry paper towel.
Condition the remaining colors of clay, from the lightest color to the darkest, cleaning your blade after working with each color.
To roll out the clay by hand:
Place the conditioned clay patty on your rolling surface (a sheet of glass or wax paper or a smooth ceramic tile or marble slab all work well, as does a piece of smooth non-stick sheet such as Teflon or Paraflexx) and lay a fresh sheet of wax paper on top of it. Use a clay roller or brayer to roll the sheet to an even thickness of approximately 2.5 mm (3/32"). You can use stacks of playing cards or clay rolling frames to help you roll out the clay sheet to an even thickness.
To condition the clay with a pasta machine:
Slice the clay into 1/4" thick slices and place them on a piece of deli wrap paper or waxed paper with the edges overlapping slightly. Press the overlapping edges so the slices stick together. Set a polymer clay-dedicated pasta machine to its thickest roller setting, lift the attached, overlapped slices and pass the clay through the rollers.
Fold this thinner, smoother sheet of clay in half and pass it back through the rollers, feeding the folded edge through the rollers first to avoid trapping air between the layers. Adjust the rollers to the next-thickest setting and repeat several more times until the clay is smooth, soft, and pliable.
To roll out the clay with a pasta machine:
Adjust the rollers to the third-thickest setting on the Atlas 150 pasta machine (or to approximately 3/32" or 2.5 mm if you are using a different brand or model of pasta machine) and pass the sheet through once or twice more.
Repeat with the remaining colors of clay.
Trim the sheets to uniformly-sized squares or rectangles with a clay blade or a tissue blade and wipe off the clay residue from the blade as before.
Make The Polymer Clay Sheets Thin for Your Mokume Gane Stacks
For the purpose of this tutorial, I kept the sheets thick so you could see the layers clearly in the photos. When you make your own polymer clay mokume gane, be sure to make the layers thinner than the ones shown in these photos. Thin layers allow more of the colors to show in each slice when you shave the stack and usually produce much nicer patterns than stacks made with thick layers.
Choosing Polymer Clay for Mokume Gane
The best polymer clay to use for mokume gane is a formula that is fairly firm and is very strong after curing. Two that I have used and recommend highly are Premo Sculpey and Kato Polyclay.
I highly recommend getting the Premo! Sculpey 24 Color Sampler set, which includes 1 oz. blocks (half the size of the regular 2 oz. blocks from this brand) in a mix of regular Premo Sculpey and Premo Sculpey Accents effects colors. It's a super value and a terrific way to try out a wide variety of colors so you know which colors you want to buy in full-size blocks. Even if you already own an assortment of Premo Sculpey polymer clay colors, this is a really inexpensive way to expand your color palette.
Kato Polyclay was developed to the demanding specifications of world-renowned polymer clay artist Donna Kato to meet the needs of professional polymer clay artists. Kato Polyclay doesn't make a huge selection of colors like the Premo Sculpey line because most professional artists prefer to mix exactly the colors they want from a smaller number of clear, saturated hues that they can blend to the desired shade and degree of transparency or opacity they prefer for a particular project. Kato Polyclay is a very firm clay, which makes it a bit harder to condition but also allows it to be sliced very cleanly with minimal distortion - an important consideration when slicing patterned canes or shaving slices of a polymer clay mokume gane stack. Another characteristic of this clay is that it can be baked at a higher temperature than most other brands and formulas and the cured polymer clay is extremely strong.
Choosing Clay Blades and Tissue Blades
There are two types of fine, thin, long, sharp blades commonly used for slicing polymer clay. One is what I refer to generically as a "clay blade", which can be rigid, flexible, or even ridged. The other is a "tissue blade", which is extremely sharp and is designed for slicing of super thin slices of human tissue...which also means that if your fingers get near the business end of this blade it can slice right through to the bone! This isn't meant to scare you, just as a warning to always to treat genuine tissue blades with your full attention and respect and mind how and where you are holding them. Sometimes clay blades are marketed as "tissue blades," so I recommend buying tissue blades from a source of medical or scientific supplies. Many of these companies sell tissue blades on eBay.
Both clay blades and tissue blades are essential tools for working with polymer clay. I recommend saving your tissue blades for when you really need them, such as for shaving slices from a mokume gane stack. Once a tissue blade loses its initial razor-sharp edge (it doesn't take many uses for this to happen), use it as a clay blade and open a fresh tissue blade for slicing your mokume stacks. Always clean your clay blades and tissue blades thoroughly after each use by folding a paper towel into a thick pad, wetting it with rubbing alcohol / isopropyl alcohol, and drawing each side of the blade firmly against the alcohol-soaked pad. DO NOT fold the alcohol-soaked paper towel around the edge of the blade and try to clean both sides of the blade at once...especially if you are cleaning a tissue blade! The blade can slice through the folded paper towel and right into your hand.
Tip: I like to color the unsharpened edge of the blade on both sides with bright red nail polish or model paint (e.g., Testors brand) or cut a narrow strip of electrical tape the same length as the blade and fold it over the unsharpened edge. That way I can tell at a glance which is the "business end" (the uncolored edge) and which is the "safe edge" (the colored edge) before I even touch the blade.
Always Use a Pasta Machine Dedicated Exclusively to Polymer Clay Use
If you plan to make more than the occasional piece in polymer clay, you'll want to own a polymer clay-dedicated pasta machine. If you want to make pasta also, you'll need a separate machine dedicated exclusively for food use. Never let uncured polymer clay touch anything that will touch food.
Choosing a Dedicated Pasta Machine for Polymer Clay Use
You can buy inexpensive pasta machines or even clay rolling machines that are essentially cheap pasta machines. But if you're going to be working with polymer clay often, I think it's well worth investing in a good quality pasta machine and taking good care of it with regular cleaning and maintenance.
The machine used by most professional polymer clay artists is the or the newer, wider Marcato Atlas 180 model. This top quality Atlas pasta machine is the universal standard for conditioning polymer clay and rolling out even sheets of clay. The Atlas 150 costs more than cheaply made machines from some craft and clay manufacturers, but it's also much better made and more durable, and it will work reliably for many years if you care for it properly. If you plan to work with polymer clay frequently, it's an investment that will pay for itself quickly. Marcato Atlas 150 pasta machine
It's also the standard reference when instructions specify pasta machine settings (i.e., roller width settings), since different pasta machines have different numbering systems and different roller width settings. When a polymer clay book or project tells you to roll out the clay "at a #3 setting", for example, it almost always refers to the #3 setting on the Atlas 150 pasta machine. Different pasta machines have different roller widths as well as settings, so if you use the #3 setting on a different pasta machine, the clay may not be the correct thickness for the project you're making
STEP 2: Apply Silver Leaf, Copper Leaf or Gold Leaf to Some or All of the Polymer Clay Sheets (Optional)
Many polymer clay artists like to include layers of metallic silver, copper, or gold leaf as part of their mokume gane clay stacks. Genuine gold, copper or silver leaf can be used, but because the cost is so high most casual polymer clay users prefer to use composition metal leaf, which also comes in beautiful variegated patterns. Using metal leaf in polymer clay mokume gane is especially effective when using tinted translucent clays rather than saturated opaque colors, but it can add a striking accent to opaque mokume gane veneers as well.
- Carefully place the trimmed polymer clay squares or rectangles on a sheet of metal leaf. Place the squares very close together to avoid wasting the metal leaf. The metal leaf will adhere to the polymer clay on contact, so be careful in your placement of the polymer squares or rectangles. Try to fit as many of them as possible on a single sheet of leaf. If necessary, use any leftover leaf plus a second sheet to cover any remaining squares or rectangles of polymer clay, or leave some of the polymer colors plain.
- Cover each clay-covered sheet of metal leaf with a smooth sheet of wax paper and roll across the clay squares or rectangles so that the underside of the clay adheres evenly to the metal leaf. Remove the wax paper.
- Trim the metal leaf around each polymer clay square or rectangle. You can use a very sharp craft knife, such as an X-ACTO with a new blade, or a tissue blade. (Make sure to put in a fresh blade before trimming the metal leaf; a sharp blade is less likely to tear the fragile leaf than a used blade.) Alternatively, if the leaf has been adhered to the clay securely, you can just tear it in between the polymer clay squares or rectangles.
- Turn over the trimmed clay sheets so the metal leaf faces up, as shown in the lower right-hand square of bright blue clay in the previous photo.
STEP 3: Stack and Compress the Polymer Clay Layers.
Decide the color order for the stacked layers. Aim for the maximum contrast between adjacent layers and also a strong color contrast between the bottom and top layers, since they will be adjacent when the stack is halved and re-stacked in the next step.
Stack the polymer clay rectangles, with the gold leaf facing up on any leafed layers. After you add each new layer, cover the stack with a clean sheet of wax paper and roll across it with a clay roller or brayer to adhere the layers. Press lightly when rolling to avoid breaking up the sheets of gold leaf too much. If the stack starts to get longer or wider, gently compress the sides of the stack to bring it back to its original footprint.
After the last sheet has been added you should have a single block of laminated layers. Trim the edges, if desired, and reserve these clay trimmings.
Again, keep in mind that I made the layers in the stack thicker for this tutorial so that you could see them more easily in the photos. You do NOT want to make your own stack layers this thick!
When you roll out polymer clay, top it with fresh wax paper and "release" the clay periodically
Wax paper prevents the clay from sticking to your roller. After every few passes with the roller, peel off the wax paper and briefly lift the clay off the rolling surface (which also may be wax paper) and lower it again. This is called "releasing" the clay. Re-cover with the wax paper and continue rolling. Releasing the clay after every few passes minimizes wrinkling, allows the clay to spread out without restriction, and prevents or reduces sticking.
STEP 4: Halve, Stack, and Compress the Layers Again.
Cut down through the center of the mokume stack so you have two identical halves. Stack the halves to make a new stack that is twice as tall and half as wide. Cover this double-height stack with wax paper and roll across it lightly to adhere the top and bottom halves without causing the gold leaf to crack or break apart.
Note: You can see in the photo below that, because I started with layers that were much too thick, I had to apply so much pressure with the roller to make the stack thin enough that the gold leaf broke apart.
STEP 5: Make a Pad or Base for the Mokume Stack (Optional)
Putting a thick pad of polymer clay underneath your mokume gane billet before you distort the layers allows you to get the most out of your mokume stack by making it easier to shave off the slices at the very bottom of the stack..
Another advantage of creating a polymer clay pad or base for the mokume stack is that if you make the top portion of the pad from a clay color that looks good with the colors you've used for the mokume stack, after you finish shaving off the last of the mokume stack, the exposed top layer of the base pad (which includes some patterned areas from the very bottom of the billet) sometimes can be quite attractive. If so, it can be sliced off in a single, thicker layer and used for other polymer clay projects, such as making them into additional cabochons that don't require a separate backing sheet.
I had not yet learned about the advantages of making a pad for the billet at the time I made and photographed the mokume stack for this lens. However, I learned about this concept subsequently at a fabulous workshop with Celie Fago, and now that I've tried it I definitely recommend it. (See note at the end of this step for more information.)
If you wish to make a polymer clay pad as a base for your mokume gane billet:
Condition 2 oz. of polymer clay by hand or with a pasta machine. If you don't care about maximizing the number of veneer slices you can shave from your stack, you can use scrap clay (or a color you don't particularly like, if you have one).
Create and shape the pad: Roll out the conditioned clay to a thickness of approximately 1/8" (a bit more than 3 mm), either by hand or on the thickest setting of a pasta machine. Fold the sheet in half from left to right like a book (with the fold at the left edge). Place the clay roller horizontally in the center of the folded clay sheet and roll the upper half of the "book" away from you. Note the length and width of the folded clay. Then [lace the roller at the center of the sheet again and roll the lower half of the "book" toward you. When rolling the folded clay, use only enough pressure to push all the air out from between the top and bottom layers and make them stick them together well. Push and compress the edges of the clay toward the center to return it to its previous folded size that you had noted.
Turn the rolled clay 90 degrees and repeat, folding the clay from left to right like a book, rolling the back half from the center to the far edge and then from the center to the near edge, and then pushing the edges toward the center. Repeat as many times as necessary so that the pad is approximately the same length and width as the mokume stack.
Optional: To get as many usable slices from your stack as possible (and possibly reveal an attractively patterned surface on the top of the shaved pad), make approximately the top 1/4 of your pad from a clay color that complements the colors in the mokume gane stack. To do this, roll out a thick sheet of clay in the desired color through a pasta machine on its thickest setting. Trim it to approximately the same length and width as the scrap clay pad and place it on top of the pad. Cover with wax paper and use a clay roller to roll from the center out to the edges in all four directions to gently press out any air between the two layers. Then roll firmly across the top from edge to edge to adhere the new top layer firmly to the pad. Trim any overhanging edges, if necessary.
Compress the edges of the pad to shape it to the same footprint as the mokume stack. Cover the pad with wax paper and roll lightly across the top to flatten it again.
Attach the mokume stack to the pad.* First, attach the clay pad securely to a smooth ceramic tile by placing the pad on the tile, covering it with a fresh sheet of wax paper, and rolling across it in both directions, making sure it is firmly stuck to the tile. Remove the wax paper. Then place the mokume stack on top of the pad, cover with wax paper, and roll across it to adhere the stack securely to the pad.
* Celie Fago uses a slightly different method for preparing the polymer clay pad. Also, her method of making the mokume billet does not involve cutting and re-stacking it to make more layers, so she makes her clay pad first and then builds the stack directly onto the pad. One advantage to this approach (vs. making the pad and the stack separately and then sticking them together) is that when you roll across each new layer after it has been added to the stack, the repeated light pressure helps the bottom layer stick more firmly to the top of the pad. Another advantage is that less pressure is required to adhere the mokume stack firmly to the pad, so there is less risk of the gold leaf layers cracking and breaking apart. The trade-off is that you can't halve the billet and re-stack the halves (because you would end up with a thick layer of the pad in the middle of your stack), and a thicker stack yields more veneer slices for approximately the same amount of effort.
If you wanted to build the stack directly on top of the pad but still make a taller stack (for a greater yield), you could trim the clay rectangles in half or quarters before stacking them, which would mean stacking two to four times as many layers individually (rather than stacking fewer layers, cutting the stack in half once or twice and then stacking those pieces to create 2x or 4x as many layers, which is quicker and easier), but I haven't tried it yet.
STEP 6: Distort the Layers in the Mokume Gane Stack.
Distorting the alternating-color layers in the stack is at the heart of the mokume-gane technique. The distortion of these layers are what exposes different areas of multiple layers on the surface when cross-sections are exposed by removing thin shavings from the stack. In this tutorial I will show you just one of several different methods for distorting a polymer clay mokume stack.
Turn the stack over, if you wish, and poke randomly spaced holes into it with the tool or implement of your choice. You can use a chopstick, a paint brush handle, a pin tool, a ball-tipped burnisher, a screwdriver, even a finger. The holes can be all the same diameter or different diameters, and they can be made with a single tool or a variety of different implements. Just make sure the holes go all the way through the bottom layer of the mokume stack.
Compress the stack to close up the holes or plug some or all of the holes firmly with polymer clay (optional).
If you want the backing sheet color to show through the holes of the veneer, you can skip this step. Otherwise, compress all four edges of the stack toward the center to close up the holes, or you can plug some or all of the holes with clay. (Each of these options creates a different type of mokume gane pattern, so I encourage you to try making several mokume stacks and trying a different hole treatment on each one.)
To plug some or all of the holes, use either a contrasting or coordinating solid color of polymer clay or, if you trimmed the edges of the mokume stack in Step 3 you can use the reserved clay trimmings. Roll the clay into small balls or roll a snake, cut short segments, taper one end and push them firmly into the holes.
Press down on the stack in between the holes, if desired, to distort the layers even more.
Compress all six sides of the stack firmly with your fingers, then cover it with a sheet of wax paper and roll across it firmly with a clay roller.
Note: When shooting the photos, I did not cover the stack with wax paper before rolling it so you could get a better view of what I was doing.
Place the stack on a smooth ceramic tile (or on the prepared clay pad on the ceramic tile), turning over the stack if necessary to ensure that the plain polymer clay side (without the gold leaf) is on the bottom.
Cover the mokume stack with wax paper and roll across it with the clay roller, making sure the stack is stuck securely to the tile or clay pad.
Set the tile (with the clay firmly attached to it) in a cool place for an hour to firm it up before continuing to Step 7.
STEP 7: Shave Very Thin Slices From the Top of the Stack.
Prepare Your Work Area for Slicing the Stack
Place the cool or chilled ceramic tile with the adhered mokume stack at the edge of a counter or table, aligning the edge of the tile that is facing you with the edge of the counter or table. Place a large, fresh sheet of wax paper on your work surface right next to the tile. Stand or sit right up against the edge of the counter or table (depending on its height) so the front edge of the tile is touching your stomach or rib cage. This stabilizes the tile so that it can't slide or move while you're shaving slices off the stack.
CAREFULLY clean a brand new tissue blade with alcohol. To do this, stack two sheets of paper toweling and fold them repeatedly to create a thick pad. Dampen the surface of the pad with isopropyl alcohol or rubbing alcohol (from the drugstore), then slowly and very carefully wipe the entire blade with the alcohol-dampened paper towel pad to clean it.
Shave the Stack
Hold both ends of the tissue blade firmly with the fingers of both hands. Always hold both ends of the blade very securely and be extremely careful not to touch the cutting surface of the blade! Remember, it's called a "tissue blade" because its intended use is for slicing off very thin layers of living tissue (e.g., for a biopsy). Angle the blade so that the cutting edge is facing toward you and the blade is almost parallel to the surface of the polymer mokume stack.
Note: The photo below shows me slicing a different mokume stack so you can see how the blade should be held.
Shave off paper-thin slices top of the mokume stack, resting the blade nearly flat on the surface of the clay and bowing it just slightly so it can shave cut down into the clay. Don't try to shave off the entire layer at a time! Small shavings around 1/2" by 3/4" are fine for beginners. Focus on making thin shavings whose thickness is as consistent as possible throughout each slice, and from one slice to another. (With practice, you'll be able to shave wider and longer slices, approximately 1/2" to 3/4" wide by 1" to 1 1/2" long.) As you shave off each slice, immediately remove it from the tissue blade VERY CAREFULLY, and flip it over and place it on the wax paper, making sure not to let it touch any of the other slices.
Note: If a slice is too thick or is of uneven thickness, cover it with a fresh piece of wax paper and roll across it lightly to level the thickness.
See Why You Want to Roll the Polymer Clay Layers Thinner Than Shown in My Photos?
As I mentioned earlier, I rolled the clay much thicker than usual in the sample mokume stack for this tutorial so that you could see the layers more easily in the stack cross-section photos. The photos of the shaved stack show why it's a bad idea to make the layers thick. Notice how the bands of color in the patterned slices are thick and widely spaced? That won't happen if you follow my directions to roll out the clay layers thinner.
STEP 8: Apply Overlapping Slices to a Polymer Clay Backing Sheet as a Veneer.
You can apply the mokume gane veneer slices directly onto to a polymer clay bead, box, or other component, or onto to a backing sheet, as I've done here in order to make cabochons.
Roll a thick sheet of conditioned polymer clay to use as a backing sheet. If you used only opaque clay colors in your stack, then you can use any color of scrap polymer clay for the backing sheet. If any of the clay colors were mixed with translucent clay, then the color of the backing sheet will affect the color of the veneer to the extent that it shows through the translucent clay portions of the pattern. I used a combination of opaque and tinted translucent clay sheets in this particular mokume stack, and I chose bright pearl blue clay for the backing sheet.
You can play around with the arrangement of the slices before you roll them onto the backing sheet. Although the photo shows this design planning being done on the backing sheet, it's actually preferable to do it on a sheet of wax paper so you don't risk having the veneer slices stick to the sheet prematurely.
Once you have decided roughly on your arrangement on wax paper (recommended), place a shaved slice from the mokume stack onto the backing sheet. Cover it with fresh wax paper and roll across it lightly to adhere it to the backing sheet clay and make its surface even with the surrounding clay. Continue to add and roll in slices until the entire backing sheet is covered with a collage of patterned slices or until you have used up all the veneer slices.
After all the slices have been added, cover the clay sheet with wax paper and roll across it with a clay roller. Then turn the sheet 90 degrees and roll again. Rolling in both directions will minimize any distortion of the pattern. Your veneer sheet is ready to use!
STEP 9: Cover the Veneer Sheet with Thick Plastic Wrap and Cut Out the Cabochons.
Choose the Section of the Veneer Pattern to Use for the Cabochon
Smooth a sheet of plastic wrap or clear plastic freezer wrap on top of the veneer-topped backing sheet. Move a clay cutter of the desired shape and size just above the surface of the plastic wrap until it frames a pleasing area of the pattern.
Polyethylene deli film sheets are ideal for this purpose because they're thicker, smoother and tougher than plastic wrap, but they're more expensive and, to my knowledge, you can only buy them in large quantities. The best alternative I've found it Glad Cling Wrap, which I find doesn't stick to itself as much as other brands of plastic food wrap. More importantly, Glad Cling Wrap doesn't react badly with the plasticizers in the polymer clay, so I can also use it to wrap and store opened packages of clay, canes, leftover mokume gane veneer sheets, etc.
Tip: Don't use Glad Press'n Seal plastic wrap for making your cabochons; the tacky surface of the wrap may stick to the clay and you won't get a smooth surface on your cabochons.
Cut out the cabochon through the plastic wrap.
Stretch and smooth the plastic underneath the cutter until it is taut, then press straight down on the cutter. By stretching the plastic wrap taut, the plastic inside the cutter will force the edges of the clay cutout into a rounded shape.
Tip: Try cutting out a practice cabochon first from the least attractive section of the veneer sheet. If your clay cutter is too sharp or your plastic wrap is too thin, the cutter may cut through the plastic wrap instead of forcing it over the clay to create nice, rounded edges. If that happens, turn the cutter upside down, cover it with a scrap of plywood or a ruler, and then press straight down on the wood to cut out the rest of your cabochons. The blunt edges of the cutter won't cut through the plastic, and the plywood or ruler will prevent you from cutting your fingers on the business end of the cutter.
Carefully lift out, inspect and smooth each uncured clay cabochon.
Examine each cabochon carefully for imperfections. If necessary, heal any imperfections by stroking across them to smooth them with a fingertip. You may want to wear a rubber glove to prevent fingerprints. This attention to smoothing the surface now will minimize the amount of sanding necessary in Step 11, which is important because more than very light sanding will remove the thin mokume gane veneer layer.
STEP 10: Cure the Polymer Clay in a Preheated Oven.
Place the uncured polymer clay cabochons on a smooth ceramic tile that has been sprinkled with cornstarch or covered with a sheet of baking parchment or plain paper, which will prevent them from sticking to the tile and prevent shiny spots on the backs of the pieces.
Cure the cabochons in a preheated oven according to the clay manufacturer's directions, using a timer to monitor the curing time and an oven thermometer to make sure the oven temperature stays within 5 to 10 degrees Fahrenheit of the recommended curing temperature. Either use an oven dedicated to polymer clay and/or general crafting or place the clay-topped tile inside an aluminum foil pan and cover it tightly with heavy-duty foil (or the lid that comes with the foil pan, if there is one) to protect your cooking/baking oven from potentially noxious plasticizer fumes. Always cure polymer clay in a well ventilated area!
When the timer goes off, remove the pan from the oven and take it outdoors to cool the pieces completely. Open the lid or foil on the far side so that the fumes inside the pan escape away from you and are carried away by the breeze so you don't inhale them. When the pieces have cooled completely in the open pan, bring them back inside.
Baking Polymer Clay in a Reliable Portable Convection Oven Makes Your Cabochons and Other Polymer Jewelry Strong and Durable
Even, Accurate Temperature and 360° Air Flow are Key to Curing Polymer Clay Properly for Strength and Durability
Many polymer clay hobbyists use a toaster oven for curing their clay. Unfortunately, most toaster ovens have hot spots and cold spots, so parts of your clay can burn (releasing noxious fumes you don't want to breathe) while other parts may be under-cured and liable to break. In addition, usually there isn't enough room between the clay and the heating elements to avoid burning the surface of the clay as it is curing, and most often the oven's interior isn't deep enough to allow the hot air to circulate around all four sides of the ceramic tile on which you cure the clay.
A convection oven is ideal for curing polymer clay because it keeps the hot air circulating constantly to maintain even heat throughout the cooking chamber, so you don't get hot spots or cold spots that can burn your clay or not cure it fully. And most convection ovens are tall, wide, and deep enough to allow the hot air to circulate 360 degrees, i.e., over, under, and around the clay on all sides.
If you plan to work with polymer clay fairly often — and especially if you want to use plain and/or tinted translucent clay, which can create truly stunning mokume gane veneer effects, among other uses, but also can darken at too-high baking temperatures — I strongly encourage you to invest in a portable convection oven dedicated exclusively for curing your polymer clay pieces (and other craft uses) if you can afford one.
I highly recommend the . It cooks and bakes extremely evenly, even with the convection feature turned off. The controls are simple and easy to learn, and I love being able to adjust the target temperature and baking time on the fly if I need to. Mine has been very accurate. I bought it originally to use as a second oven for cooking and baking, but I'm planning to order a second one to use exclusively for curing polymer clay. Black & Decker CTO6335S Stainless Steel Countertop Convection Oven
STEP 11: Wet Sand the Cured Polymer Clay.
Use a Range of Grits, Starting With the Coarsest Grit and Progressing Through to the Finest Grit
Fill a container with water and a drop or two of liquid dish washing soap, which serves as a sanding lubricant. I use a small plastic dishpan dedicated exclusively to sanding polymer clay. Use automotive-grade wet/dry sandpaper (silicone carbide abrasive) and/or Micro-Mesh Soft Touch sanding pads to wet-sand the cabochons. It is essential to use wet/dry sandpaper or sanding pads since you will be wet sanding, and automotive-grade wet/dry sandpaper is far superior to regular wet/dry sandpaper. Start with 400-grit followed by 600-grit and 800-grit. Continue to 1,000-grit (and even higher, if you wish, for a smooth-as-glass finish) if you plan to buff your polymer clay without sealing it with a clear coat afterward.
Important Polymer Clay Sanding Tips:
- NEVER dry-sand polymer clay! Cured polymer clay sanding dust is not something you want to breathe into your lungs. Wet-sanding the clay prevents the particles from becoming airborne so you won't breathe them.
- Rinse the container and refill it with fresh water and a few drops of liquid dish soap before switching to the next-finer sanding grit. Otherwise bits of the coarser sanding grit in the water can scratch the polymer clay.
- Stop sanding as soon as the surface of the polymer clay is smooth! Removing too much of the mokume gane veneer can alter the pattern significantly or even remove it completely in spots, revealing areas of the solid color backing sheet.
- Rinse and dry the sanded cabochons thoroughly in fresh running water. If I am planning to apply a polymer clay glaze or compatible clear coat, after I dry them I usually set them aside in a warm, dry place for an hour or two (just to make sure no moisture vapor remains).
Automotive Grade Wet/Dry Sandpaper in a Range of Grits
For wet sanding polymer clay, wet/dry sandpaper (sometimes called "wet or dry sandpaper") is essential. Automotive grade sandpaper will give you a MUCH smoother surface than regular sandpaper from the hardware store, and it also will last longer during wet sanding. You'll need a range of grits from 400 grit through 1000 grit (or up to 2000 grit) if you plan to buff your cabochons. If you are planning to glaze or seal your cured polymer clay cabs (an essential step if you used metal leaf on any of the layers in the mokume gane stack), you may stop at 800–1000 grit sandpaper if you wish.
You can buy automotive grade sandpaper at a local auto parts store. I recommend 3M Imperial Wetordry Sandpaper.
STEP 12: Buff, Seal or Glaze the Polymer Clay as Desired.
Buff the Cabochons to a Soft Sheen
For a soft sheen finish, buff the polymer clay cabochons with a scrap of denim fabric, preferably white (cut up an old pair of jeans or buy 1/4 yard at a fabric store) or use a motorized, variable speed jeweler's polishing lathe or bench-top polisher fitted with a clean, loose, unstitched muslin buffing wheel attachment. If using a motorized buffer, always use a slow-medium speed (the "Polishing" range, NOT the "Buffing" range) when buffing polymer clay; otherwise the heat generated at higher speeds can soften the cured polymer, in which case buffing wheel will "melt" the cured clay so that it smears or leaves depressions in the surface.
Important Safety Tip: Always follow the safety guidelines that come with your polishing lathe or motorized buffer. Buff by hand unless you know how to use this equipment safely!
You Must Seal or Glaze If You Used Metal Leaf (Other Than Genuine 24K Gold Leaf) in Your Mokume Gane Stack
If you have used composite gold leaf (or other metal leaf other than pure 24k gold leaf, which is very expensive), buffing is optional. However you will need to apply a coat of polymer clay-compatible glaze or other clear coating to seal the mokume gane veneer surface. Otherwise the metal leaf will oxidize (i.e., tarnish) over time with exposure to the air.
Even if you have used 24k gold leaf (or no metal leaf at all), you may decide to clear coat your sanded mokume gane pieces with a polymer clay compatible glaze or sealer if you prefer the look of that finish.
Polymer Clay Compatible Glazes
Sculpey Glaze (which comes in a choice of glossy or matte finish), Pledge FloorCare Multi Surface Finish and Varathane Diamond Water-Based Interior Polyurethane (satin, gloss or semi-gloss finish) all are polymer clay-compatible.
SC Johnson manufactures several different formulas of Pledge Floor Finish. For glazing or sealing polymer clay, buy the Pledge FloorCare Multi Surface Finish formula, not the wood floor care formula. You should be able to find it in your local supermarket or home improvement store, e.g., Home Depot, Lowe's. Also, Rust-Oleum makes several different formulas of Varathane Diamond Polyurethane. Make sure to buy the Varathane Diamond Water-Based Interior Polyurethane formula.
You can find large cans of Varathane Diamond Water-Based Interior Polyurethane in your local hardware store or home improvement store, but I highly recommend ordering the small 1/2 pint cans from Amazon, which are a much more convenient size for polymer clay use and less expensive, since you will use only a little at a time.
Clear UV Resin
A third option is to apply clear UV resin to the polymer clay and cure it under a UV lamp or other ultraviolet light source as directed, which will give your pieces a glass-like shine. Make sure to check with the manufacturer whether the brand you choose will be polymer clay compatible. I have used Lisa Pavelka's Magic-Glos UV Resin successfully with polymer clay. It costs more than two-part UV resin formulas but there's no guesswork in trying to get exactly equal quantities of part A and part B, so it's less risky and less wasteful than cheaper two-part formulas.
Tip: It's much more economical to buy the 6 ounce bottle than the 1 oz. bottle, but it does have a limited shelf life. If you plan to cover a lot of pieces with resin, the larger size is definitely worth it. If not, get the smaller one.
Liquid Polymer Clay
Another option is to brush on a thin coat of liquid polymer clay and put the pieces back into the oven to cure according to the liquid polymer clay manufacturer's directions.
Popular brands include Translucent Liquid Sculpey, often referred to as TLS; Donna Kato's Kato Liquid Polyclay; and FIMO Liquid Decorating Gel, which I find produces the clearest, most glass-like glaze finish.
Finished Polymer Clay Mokume Cabochons
Here's a photo of some of the polymer clay cabochons I created for a project article I wrote for Vol. 2, Issue 3 of Metal Clay Artist Magazine that was published in Spring 2011.
These versatile polymer clay cabochons can be framed with polymer clay or metal clay, or even set into commercial cabochon settings if you create your cabs in one of the standard calibrated cabochon sizes, such as 8x6 mm or 18x13 mm.
Have fun making your own polymer clay mokume gane cabochons!
Questions & Answers
© 2012 Margaret Schindel