Metal Clay Tips for Success
Make it golden! Add gold to your complex or deep-textured silver pieces with gold paste. Follow these tips and hints for perfect application success.
This tip covers adding a 22k gold finish to any complex, fired fine silver piece. Keum-boo is an ancient Korean technique that uses heat to permanently bond thin gold foil to fired silver — but it can be difficult to apply on complex shapes and textures, such as faces and braids. A simple, fast alternative is gold paste*, using Art Clay Overlay Paste as an intermediary to ensure adhesion.
- Make sure your fired silver piece is clean, but do not brush or polish the areas where you will apply the gold paste.
- Stir the Overlay Paste with a spatula, then apply it only to the areas where you want the gold. Cover those areas completely and smoothly, and allow it to dry fully. Add more if needed.
- Stir the gold paste with a fine metal tool — not a wooden toothpick, which will absorb the gold and waste it.
- Rinse your fine brush completely with water and dry it, then load just the tip with gold paste. Paint over the Overlay Paste, covering it completely with an even layer so that no white is visible beneath. Allow to dry fully. Touch up any areas where white shows through. When enough gold paste has been applied, the entire area will appear flat and mustard-colored.
- Place the piece on a refractory fire brick and use a butane or propane torch to slowly and evenly heat the entire piece until it glows a salmon color. Hold it at that temperature for up to two minutes. Turn off the torch, then immediately use an agate burnisher to burnish the gold paste areas while the piece is still hot, applying firm pressure. Stabilize the piece with tweezers in your other hand if needed. If the piece is too complex to reach every detail, do the best you can. When fired correctly, the piece can be tumbled without losing any gold, and will come out smooth and shiny.
Are you sure it’s completely dry? Many problems can occur when metal clay pieces are not thoroughly dried before firing. Here’s a great way to be sure the piece you worked so hard to make is ready to be fired.
- Have a piece of thin, flat metal ready at room temperature — a clay cutter, the lid of a hand balm tin, or something similar will work well.
- When your piece is thoroughly warmed, remove it and immediately place it on the metal surface. It is important not to let the piece cool before testing. Count to at least five, then move the piece aside. If any moisture remains, it will leave a ring of condensation between the piece and the metal beneath — a clear sign that the piece is not yet ready to fire. Return it to your drying setup for another ten minutes or so, then repeat the test until no moisture is detected.
Pass the torch! No kiln? In a hurry to fire a small metal clay component or piece? Here are the keys to torch firing success.
There are three common methods for firing silver metal clay: butane or propane torch, gas stovetop, and electric kiln. The electric kiln is the most straightforward — the target sintering temperature and ramp speed can be programmed in advance, and once started, the kiln will complete the process automatically. Torch firing is a very different experience, however, and requires close, continuous monitoring.
Working with an open flame
Silver melts at approximately 1,761°F/961°C, so your flame must stay below that temperature at all times. Hand-held butane and propane torches can reach that threshold if distance is not carefully managed. Because there are no temperature controls on a hand-held torch, heat is governed by two factors: time and distance. When sintering fine silver with a torch, color and time are your guides to knowing when the proper sintering temperature has been reached and held.
Before you begin
- Dim your work area. Because the color of the heated piece is a critical indicator, working in a bright environment can give you a false reading and cause you to overfire — partially or fully melting the piece.
- Set a timer for four minutes, but do not start it yet.
- Check that your torch is full of fuel and functioning properly. If your butane runs out before sintering is complete, you will need to refill and start the process over from the beginning.
Firing
Begin heating the piece by sweeping the torch slowly back and forth, holding the flame about one inch away. You will see smoke rising from the piece as the binder ignites and burns away — there may or may not be a visible flame. This is normal. Pull the torch back slightly while maintaining the sweeping motion.
The smoke will subside, and the piece will begin to glow: first a dusky pink, then dusky salmon, and finally a bright salmon color. Your goal is to keep the entire piece glowing a steady, bright salmon. If you cannot heat the entire piece evenly, it is too large for torch firing and will need to be kiln fired.
Start the timer.
Continue moving the torch to keep the entire piece engulfed in heat and glowing evenly. Do not hold the flame in one spot. Watch for shimmering in the metal — this is a warning sign of imminent melting. If the color moves past salmon toward cherry red, increase the distance between the torch and the piece until the bright salmon color returns. You do not need to turn the piece over as long as the color is consistent across the entire surface.
A reassuring note: If you lose track of time or miss the timer, don’t panic. As long as you maintain that bright salmon color and do not allow the piece to overheat, it will be fine. You cannot overfire a piece simply by holding the temperature — you can only damage it by letting the torch get too close and allowing the temperature to climb above approximately 1,600°F/871°C, which will show as cherry red or a shimmer in the metal’s surface.
After firing
When the timer goes off, turn off the torch and allow the piece to cool naturally. You can speed up cooling by moving the piece with tweezers to a cooler area of the brick, a cold brick, or a cold metal surface. Quenching in cold water is an option some artists use, but it is not required.
Once cool, you should see the shrinkage that occurred during sintering. The surface will appear white as fine silver comes to the surface — it is now ready to be brushed, burnished, or polished.
Leave the grind behind! Short on time? Skip the tedious step of grinding the clay to powder by following these steps.
If you have an old, unopened package of silver clay that has hardened and become unworkable, you do not need to grind it to powder to use it again. Followed patiently, this tip will restore that hard lump to smooth, malleable clay.
Remove the clay from the package and transfer it whole into a small resealable plastic bag along with a small piece of wet, folded newspaper. Do not use a paper towel — paper towel will draw moisture away from the clay and prevent rehydration, whereas newspaper helps transfer moisture back into it.
Before sealing the bag, add distilled water according to the weight of your clay:
- ¼ tsp. per 10g of clay
- ½ tsp. per 20g of clay
- 1 tsp. per 50g of clay
Work the water into the clay through the plastic as best you can, then seal the bag and leave it for 24 hours.
After 24 hours, remove the newspaper and add several more drops of distilled water, continuing to work it into the clay through the bag. Repeat this step daily for as many days as needed until the clay has rehydrated into smooth, workable consistency.
Alternative method: If you prefer to work more quickly, place the hardened clay in a plastic bag and break it into as many small pieces as possible using a hammer. Then use a mortar and pestle or a dedicated coffee grinder to reduce it to a fine powder. The clay cannot be reconstituted with water unless it is ground finely enough — use a small enamel sifter to sift small quantities at a time until the texture is completely uniform. There must be no grains, lumps, or fragments remaining in the powder. This is why the newspaper-and-water method, though slower, is often the better choice — it reconstitutes the entire lump without the extra steps.
Make It shine! Whether you choose a matte or mirror finish, proper finishing before firing is essential to achieving a professional look. Here are tips for getting a perfect mirror shine.
After a successful firing, your piece will appear white — this is completely normal. Fine silver is white in its natural state. Your next decision is what kind of finish you want, and this is where your pre-finishing work becomes very apparent. Whether you choose a matte or mirror finish, any cracks, pits, or surface imperfections that weren’t filed, sanded, and filled before firing will be much harder to address now. As the saying goes: garbage in, garbage out. Prepare your surface well before firing, and the finishing process will reward you.
Starting with a matte finish
Assuming your pre-finishing was thorough, the usual first step is to brush your piece with a stainless steel brush, which will produce a smooth, satin finish. Some artists reach for a brass brush, believing it will leave a smoother result — however, brass can sometimes transfer color to the silver, so it is best avoided.
Achieving a mirror finish
A true, hand-done mirror finish takes time and patience. Prepare three small bowls of clean water and label them 600, 1,200, and 2,000 grit. Labeling matters — you will understand why shortly. Alternatively, sanding pads in the same grits can be used in place of sandpaper and have the advantage of losing less grit in the water.
Tip 1: Fold your sandpaper. If using sandpaper sheets, fold each piece into quarters so that no bare or cut edge is exposed. Dragging an unpadded edge across your piece can leave a groove that is difficult to polish out. If using sanding pads, simply curve the pad as you work so you are never sanding with its edge.
Tip 2: Always sand wet. Wet sanding produces a far superior result to dry sanding. Begin with the 600-grit paper or pad — this is the most important stage and deserves the most time. Sand in a consistent horizontal or vertical direction, applying firm pressure, until the surface is even. The piece will not look like a mirror yet, but you are laying the foundation for one.
Tip 3: Use clean water every time you change grits. This is the most critical step, and the one most often overlooked. If you rinse your 600-grit paper in a bowl of water and then dip your fresh 1,200-grit paper into that same bowl, you have just reintroduced coarser particles onto a finer paper — and onto your piece. Always move to a clean bowl of water with each grit change. With fresh water and a new piece of folded 1,200-grit paper, sand perpendicular to your first direction. You will begin to see the polish developing.
For the final pass with 2,000-grit paper and the last clean bowl of water, sand in small circular motions. You will feel little to no resistance — the surface debris has been removed and the silver is approaching mirror smoothness. Rinse and dry the piece thoroughly before moving on.
The final step most people miss
Many artists stop here and wonder why they cannot see their reflection in the piece. Every silversmith keeps some form of silver polish on the bench — Wenol, Pikal Care, and similar products all work well. Apply the tiniest amount to a soft cloth and rub in a circular motion with moderate pressure. The result will be an eye-catching shine that makes all the work worthwhile.
If you still are not achieving the finish you were looking for, the culprit is almost always the 600-grit stage — it was not done hard enough or long enough. Change all the water in the bowls and start again from the beginning. The path to a mirror finish has many variables, but the result is worth every step.
Draw the line! A metal clay syringe is a fabulous tool for joining greenware and repairing cracks. It is also a great tool for drawing lines, writing, making mesh designs, and other decorative techniques. Here’s how to use the syringe to draw like a pro.
Many brands of metal clay are available with pre-filled syringes, which can be used to join two pieces of unfired greenware, repair cracks and pits, and create decorative effects such as drawn lines and mesh-like designs. The clay inside the syringe is a consistency somewhere between workable clay and paste — fluid enough to extrude smoothly but substantial enough to hold its shape.
This tip is about drawing with the syringe successfully. The goal is to extrude clay in a round, even, unbroken line that lands exactly where you want it and starts and stops cleanly.
How to hold the syringe
Hold the syringe loosely in the palm of your dominant hand, with your first through fourth fingers around the barrel. If you are right-handed, angle the syringe approximately 45 degrees to the right — not straight up and down.
Most importantly, use the second pad of your thumb — not the tip — to depress the plunger. Nearly every beginner instinctively uses the tip of the thumb, which tires quickly and causes the hand to tighten around the barrel. That tension is what produces the squiggly, uncontrolled lines that frustrate so many new artists. The second pad gives you far more control and endurance.
How to draw the line
Before you begin extruding, touch the tip of the syringe to the surface. Watch closely, and the moment you see clay beginning to emerge, lift the syringe just above the surface and guide it along your intended path. Do not drag or pull the syringe along the surface — this will thin and distort the line and force you to start over. Think of it as laying the clay down gently rather than painting it on.
You will need to coordinate the speed at which you are extruding with the speed at which you are moving the syringe. If those two speeds are out of sync, the line will be uneven. Practice on a piece of Teflex until the hand-eye coordination feels natural.
To end your line cleanly, stop extruding first, then touch the tip of the syringe back down to the surface before lifting it away.
What you can do with it
Once you have mastered syringe control, the applications are nearly limitless — creating stone bezels, cells for cloisonné or champlevé enameling, decorative mesh patterns, and even writing names or words on greenware pendants and tags.
To Quench or Not to Quench? There are times when it’s OK to quench your metal clay and times when it isn’t. Do you know the difference?
As metal clay formulations have advanced, a large number of silver clay artists — and especially instructors working under time constraints — have adopted the practice of preheating their kiln to 1,400°F/760°C or 1,600°F/871°C and holding it at temperature until they are ready to fire. They set a timer for the appropriate firing duration and, when done, remove the pieces and quench them immediately in cold water. Most of the time this works perfectly well. However, there are situations where loading greenware into a preheated kiln is inadvisable, and others where immediate quenching can result in a total loss.
This tip is simple but essential: know when and what to quench — and when not to.
Silver clay alone
Pure silver clay is almost always safe to quench — the exception arises when something else has been incorporated into or alongside the piece that cannot tolerate sudden thermal shock.
Gemstones
To be safe, never quench a piece that contains gemstones, even lab-created stones such as cubic zirconia. Both natural and lab-created gemstones share a crystalline structure. Natural stones often contain inclusions, bubbles, or micro-fractures that can worsen — or cause the stone to fracture, crumble, or shatter — when plunged from kiln temperature into cold water. Lab-created stones may appear flawless, but their crystalline structure makes them equally vulnerable to thermal shock.
Porcelain and glass
Incorporating porcelain or glass into a silver clay piece is a wonderful way to add color and individuality, but neither material can survive an abrupt transition from extreme heat to cold. Both must cool slowly from the outside inward and should remain in the kiln until they have reached room temperature naturally.
Bronze, brass, and carbon firing
Some specialty metal clays can be kiln-fired without carbon, but most alloy clays — such as sterling silver, bronze, or brass — require firing in carbon. This method presents a practical challenge: by the time the pieces are excavated from the carbon, firescale has often already begun to form, making the rapid quench that works so well for pure silver clay far less straightforward.
Not what it seams. Why is that pesky seam or repair showing up again and again? Successfully connect seams and make repairs with paste and syringe by taking these steps.
Have you ever made a ring, joined the seam with syringe clay and paste, let it dry, and sanded it smooth — only to have the seam reappear? And then reappear again? Here is your tip for success.
- Whenever you are joining, filling, or repairing, reach for syringe clay first, before paste. Syringe clay is thicker, fills more effectively, and you need less of it. Wet your brush and use it to work the clay into all the cracks and crevices, then smooth the surface.
- You can always sand away a little more, but if you fill only to the surface level, sanding will expose the seam again. Overfill — then overfill again.
- Finally, look at your piece more than you sand it. Sand a little, then stop and examine the surface carefully. Repeat. If you are working in a class, keep your focus on your piece rather than the conversation around you. Your seam will tell you what it needs.
Embrace the carbon. Be kind to your base metal clay work and fire in carbon. No firescale, no pickling, no regrets.
Some metal clays require a reduction atmosphere to fully sinter — meaning that as little oxygen as possible should be present during firing. When oxygen combines with heat, it forms an oxide known as firescale, which appears as a black coating on the surface of the piece and must be removed after firing. Torch firing copper not only risks undersintering but also guarantees a layer of firescale that will need to be addressed.
For artists without access to a kiln, torch firing is the only option, and the tradeoffs must be accepted. For everyone else, it is worth thinking carefully before reaching for the torch in the name of saving time. Here is why carbon firing in a kiln is the better choice.
The firescale problem
Firescale is not a thin film — it can build up to 1mm thick, and removing it takes that layer of surface detail with it. To compensate, pieces need to be made 1mm thicker from the start, and whatever metal is lost to firescale removal is simply wasted.
If you are lucky, quenching your hot piece in cold water directly from the fire brick will cause some or most of the firescale to flake away. Whatever remains will need to be picked off by hand or dissolved in a pickling solution — an acid formulated specifically for this purpose. Traditional pickle is toxic and cannot be disposed of down the drain. A milder alternative is acetic acid, which is available under various product names, but it is considerably weaker and requires significantly more time. Either way, there is picking involved.
Why carbon firing in a kiln is worth it
Carbon firing removes most of these headaches, and it applies to all metals that require a reduction atmosphere. Here is how to do it well.
- Load your pan by placing your pieces in activated carbon, leaving at least 1-inch/2cm of carbon on the bottom, on each side, and between layers. Cover the top layer of pieces with at least 1-inch/2cm of carbon before firing.
- Raise the pan off the kiln floor by at least 1/2-inch/1.25cm — even a scrap of fiber board will do. This is essential. Without clearance beneath the pan, the kiln’s insulation will block heat from reaching the bottom layer of carbon, and the pieces resting there may not sinter fully.
- Follow your clay brand’s firing instructions for time and temperature. At the end of the firing cycle, remove the pan from the kiln when you are comfortable doing so and allow it to cool to room temperature. Leave your pieces in the carbon until they are cool enough to handle safely.
Under these conditions, firescale will not form. No pickle, no picking.
A note on cleanup: carbon firing is generally clean, but if you are using a stainless steel pan, be aware that a black, soot-like residue can settle on the interior walls of the kiln and will need to be vacuumed out after firing.
The bottom line
The choice is yours — but there is no need to fear activated coconut carbon. Master it, and it will become one of your most reliable tools.
Practice makes progress! Try out and practice new techniques with inexpensive materials before firing silver.
Perhaps the most important tip of all is this: practice before you fire.
Whether you are new to metal clay or an experienced instructor, any time you are trying a technique for the first time — keum-boo, mokume gane, ornate filigree in paper type, or anything else unfamiliar — work through the basics before committing expensive silver. Use polymer clay, paper, or even toothpaste loaded into an empty syringe to simulate the process, and make notes along the way. When you feel confident, then reach for the metal clay.
With the price of metals today, costly mistakes are something no one can afford. Yes, failed pieces can be melted down for casting or drawn into wire — but that is never the outcome any of us are working toward. Practice, and set yourself up for success.
Authors: Jackie Truty and Katie Baum, Editor: AJ Newell