How to Dry Metal Clay
Metal clay pieces made from silver, gold, copper, bronze, or other base metal clay formulas must be completely dry, all the way through to the center, before firing them. If even a small amount of moisture remains in the center of the clay, it can cause problems, including warping, blisters or bubbles (air pockets caused by steam that is created as the residual moisture is heated), or even craters, if the blisters or bubbles burst open under the force of the steam's pressure.
There are multiple methods for thoroughly drying your metal clay pieces before kiln firing or torch firing them. This article reviews the pros and cons of each option to help you chose which is best suited to your needs.
Metal Clay Drying Methods: The Trade-Off of Speed vs. Even Drying
In general, choosing a method for drying metal clay involves making trade-offs between speed and even drying. When you're creating a new piece, it's easy to be a bit impatient and crave instant gratification.
Unfortunately, using an electric cup or mug warmer or a hotplate to dry your metal clay pieces as quickly as possible often causes them to warp or crack, unless they are both thin and fairly small. As the clay dries, it shrinks somewhat (although not as much as during firing). So, if the bottom of the piece dries significantly sooner than the top, or if the surface of the clay dries much faster than the interior, the parts that dry first shrink before the parts with more moisture, potentially leading to warping or cracks. The thicker or larger the piece, the more unevenly the clay will dry.
The good news is that these problems can be minimized or avoided by choosing a slower, gentler drying method, especially for thicker or larger metal clay pieces, and placing them on a surface, such as open-cell foam or smooth wire mesh, that lets air circulate under, over, and around the piece. The goal is for the top, bottom, sides, and interior to dry at the same time, and at as close to the same rate as possible.
A Word About Warping
Metal clay tends to warp as it dries when the entire piece does not dry evenly at the same rate. The center of the clay dries last, as it is not directly exposed to the air, so the more slowly you dry the clay, the more evenly it will dry and the less prone to warping it will be.
Of course, it's natural to be impatient for your clay to dry so that you can refine it, assemble it with other pieces, if necessary, and fire it. Just be aware that, in general, the more you accelerate the drying process, the less evenly your clay is likely to dry and the more susceptible to warping it will be.
The best way to avoid this is to air-dry pieces rather than drying them with heat, and if possible, to dry them in a way that allows air to circulate around all sides of the clay at the same time. Air drying on a piece of soft, open-cell foam sheet lets metal clay pieces dry evenly but it's fairly slow. You can accelerate the drying process by placing the clay (on the foam sheet) into a food dehydrator to increase the air circulation. Ideally, using a no-heat setting is best and will dry the clay most evenly. However, you can use a low heat setting, if you wish (never use medium or high heat). If you choose to use the low heat setting, don't leave the metal clay in the dehydrator too long to avoid warping. You also can make a homemade metal clay drying box to use with a hand-held hair dryer aka blow dryer.
If you are going to dry metal clay on nonstick sheet or another nonporous surface, you can help minimize warping by not lifting your clay from the sheet after the last pass with the clay roller, and after cutting the desired shape, removing the excess clay without lifting the edges of the piece you have cut out. The nonstick sheet has a very slight texture that grabs onto the clay a bit, so the clay is less likely to curl up at the edges if they remain adhered to the sheet.
If you are going to use a hotplate or cup warmer to dry your clay faster, you'll need to monitor the drying and flip the piece over frequently to minimize warping.
The rest of this article will go into more detail about each of these drying methods and their respective pros and cons.
Air-Drying on Open-Cell Foam Sheet
Especially for volumetric pieces that aren't being dried over/around a support, it's a good idea to air dry the fresh clay on a piece of soft, open-cell foam sheet 1/2" to 2" thick. It is often sold by the yard at fabric stores and is sometimes used for upholstery.
- Use foam that is soft and squishy (not dense), which is filled with air pockets and will allow air to circulate around all sides of the clay. This will speed up the drying process somewhat and also eliminate the need to flip the piece over in order to dry both sides.
- Another benefit is that it prevents the clay's surface (whether smooth or textured) from being marred while it's still "wet."
- If you can't find this type of foam by the yard, you can use the thicker piece of foam from a package of Wilton Fondant Shaping Foam or the Ateco Molding Mat for fondant. Both are made of food-grade foam and designed for drying soft fondant cake decorations.
Make a Folded Foam Drying Support
Celie Fago taught me a neat trick, which is to fold a piece of the foam sheet accordion-style to fit inside a drinking glass, mug, jar, etc. While you wouldn't use this method to dry fresh metal clay pieces, there are two situations in which it's extremely useful.
If you want to attach a new element to the edge of an already dried piece, you can carefully place the greenware inside one of the folds in the foam sheet, so that the piece is vertical (I.e., perpendicular to the work surface), with the edge where the new element will be attached at the top. The foam should hold the piece in that vertical position while the new element is attached and the joint dries.
If you are joining two dry metal clay components, such as adding a tube bail to the top edge of a pendant, keeping the pendant vertical makes is less likely that gravity will cause the bail to roll to one side, or even fall off completely.
If you are joining a fresh clay element to the edge, maintaining the perpendicular orientation will help the moist clay addition to dry without being marred or distorted by gravity.
The photo shows an example of a dried copper clay kimono that I propped up vertically in the folds of the foam so that the fresh copper clay collar pieces I attached could dry without flattening, marring or sagging—all of which would likely have happened if I had laid the pendant flat to dry after adding the collar. You can also see the fragile, slender, tapered copper clay rod in another fold in the same piece of pleated foam sheet. The rod had broken in the center, so I used the foam to hold one of the broken halves vertical, with the broken edge at the top. After I repaired it very carefully, with the top half balanced precariously on the bottom half, gravity helped hold the halves together while the fresh clay I used to join them dried.
If I had tried to dry the rod horizontally, gravity would have made the tapered ends sag rather than remaining on a straight axis, pulling the two halves apart before the fresh clay repair had time to dry.
The folded foam sheet drying support is also extremely helpful for holding dry metal clay components together securely after you have joined them with fresh clay, paste, slip, or another metal clay “glue,” such as Aussie Metal Clay’s ClayStay. Nestling the newly joined pieces inside a fold in the foam sheet will hold them together with gentle, even pressure as they dry, helping to keep them in the correct position as the joint dries and facilitating a more secure bond.
Using a Food Dehydrator
A food dehydrator is an excellent way to dry metal clay, providing gentle, even drying when used on low to no heat. The dry, circulating air speeds up drying significantly and is less likely to result in warping than a direct heat source, such as an electric cup or mug warmer or a hotplate.
It's important to use a dehydrator that allows you to dry with no heat or very low heat to minimize the chances of warping.
To protect the fresh metal clay from becoming textured by the mesh screen shelves in the dehydrator, always line the shelf with a piece of nonstick sheet before drying your clay. To further decrease the chance of warping, especially if you are using (low) heat, either use the same piece of nonstick sheet on which you rolled out your clay (without lifting the edges of the clay from the sheet after rolling or cutting) or place it on a piece of foam sheet and put the foam on top of the nonstick sheet in the dehydrator.
Choosing a Dehydrator for Metal Clay
Some of the features to consider include the usable tray space, whether it has a thermostat, where the heating element is located, the efficiency of the airflow, the spacing of the trays, the warranty and the company's customer service reputation/track record.
Round food dehydrators are the most commonly use type for drying metal clay. Here are the advantages of this type:
- Most are fairly inexpensive; sometimes you can find them used or at yard sales.
- They're very common, so they may feel more familiar.
But they also have several disadvantages:
- Most are designed with the heating elements and fans at the bottom, so the temperature varies significantly from the bottom tray to the top tray.
- How efficiently the fans circulate the air can vary widely from one brand or model to the next.
- These units are round and the drying trays are doughnut-shaped, which cuts significantly into their usable area. In fact, you may lose as much as 25% of the tray space because of the "doughnut hole" in the center.
- They trays are stacked so that they rest directly on top of one another. That means means you need to lift off not only the lid but also the upper trays when you want to load or unload pieces on the lower trays.
- The trays are fixed-height, so if you need to dry something tall (or on a piece of foam), you'll need to jury-rig height spacers. You can do this fairly easily by placing three drinking glasses (or even sturdy foam cups) spaced equally around the tray in between your metal clay pieces. However, that not only cuts further into the usable space but also opens up the sides, which prevents the air from circulating efficiently or evenly.
Square Excalibur® Dehydrators
If you're a professional metal clay artist and can justify the cost, square Excalibur brand dehydrators are the best and most versatile on the market. Advantage include:
- Excalibur dehydrators are square and feature a unique and efficient design that gives you use of the entire surface of each tray. You can dry many more pieces at a time, or much larger pieces, than you can in a round model with open-centered trays.
- The trays slide in and out from the front, like drawers. That means:
- You can pull out a tray with one hand and load your pieces onto it with the other hand, which makes loading and unloading much faster.
- You can remove some of the trays to accommodate taller pieces (or pieces that are sitting on a piece of open-cell foam).
- Excalibur dehydrators have built-in thermostats that allow you to control the temperature within a fairly wide range. So you can reduce the temperature to very low to minimize warping. This is a major benefit!
- The company's unique ParaFlexx™ Horizontal Airflow drying system creates a much more efficient airflow for faster, more even drying.
- They come with a generous warranty—5 or 10 years, depending on the model and where you purchase it.
Of course, all these features come at a price, and Excalibur dehydrators are significantly more expensive than those from other manufacturers. However, if you make a lot of large pieces, do production work (or just make a lot of pieces at a time), or teach metal clay classes, you may want to consider investing in one. For maximum drying space and versatility, I recommend the 9-tray model. There are less expensive knock-offs, but they don't have the same quality, reliability or service and support as genuine Excalibur units. Excalibur 3926TB dehydrator
Using a Homemade Drying Box and a Hairdryer
For drying metal clay, the next best thing to a dehydrator is a homemade drying box. The simplest and cheapest version is simply a cardboard box with a hole cut into one side of the box just large enough for the nozzle of a handheld hairdryer, aka blow dryer, to poke through. Here's one way to make one.
Making a DIY Metal Clay Drying Box
- Find a cardboard box. such as a shipping box from a package delivery. Ideally, it should be approximately 12 inches deep.
- Cut off the open flaps on the top. As an alternative, you can fold the flaps inside, as long as they will stay flat against the sides of the box.
- Cut an opening in the bottom of the box that will fit the nozzle of your hairdryer snugly.
Using the Drying Box
- If your metal clay piece has a flat bottom or back, try to leave it on the piece of nonstick sheet you formed it on, if possible, and . Otherwise, place your metal clay piece (or pieces) on piece of nonstick sheet or open-cell foam. You also can place your clay pieces on a a raised platform or shelf made from a piece of fine stainless steel mesh or screen, which will allow the air to circulate underneath the clay as well as over and around it. Choose a fine wire mesh to minimize any marks on the back of the clay, unless you like the light texture created by the mesh.
- Place the dryer box upside down and centered over the clay.
- If your blow dryer has a concentrator or diffuser attachment on the nozzle, remove it. Then, poke the nozzle through the opening on the side of the box. The nozzle should parallel to the top of the box, so the warm air will blow across the box and above your metal clay pieces.
- Set the hairdryer to low speed to avoid blowing the piece around, and to low heat to minimize cracking or warping. Then turn on the power button or switch.
- Allow it to run for at least 5–10 minutes (assuming you want you piece to be bone dry). Every few minutes, turn off the power, lift off the box, and check the top of your piece for dryness.
- When the top has dried completely, turn the piece over and repeat to dry the back.
Note: The length of time required to dry your metal clay piece thoroughly will depend on a variety of factors, such as the size and thickness of the clay, the porosity of the surface you are drying it on, the size of your box, the location of the opening, and the speed and temperature of the hairdryer. Typically, pieces that are a few cards thick and not very large need approximately 10–20 minutes in total to dry on both sides.
Fine Stainless Steel Mesh Racks for Drying Metal Clay
Stainless steel mesh screen made from fine wire is very good for making racks or shelves for drying your metal clay pieces. The air can circulate all the way around pieces that are elevated on the mesh rack, and the fine wire mesh minimizes the likelihood of a pattern imprint on the back of the clay.
You can cut squares or rectangles of mesh to the desired size with wire cutters (or buy a piece that has been cut to a convenient size, which is more convenient but also more expensive for the same amount of mesh). , is a good choice. 304 stainless steel mesh sheet, 20 x 20 mesh with a 0.0016" wire diameter and 46% open area
To make a drying rack, lay the wire mesh over an open frame (or raise the edges with stacks of thickness spacers, the type used to roll out metal clay) or make a drying shelf by grasping each corner of the mesh at a 45-degree angle with parallel pliers and bending it down 90 degrees, thereby creating four "feet."
Air Drying on Nonstick Sheet
Another option is to place your metal clay piece or component on piece of nonstick sheet. After one side is dry, flip the piece over and allow the other side to dry.
Another tip I learned from Celie Fago is to roll out the clay on the nonstick sheet, cut out the shape, and take care not to lift or loosen it from the nonstick sheet when you remove the excess clay from around the shape you just cut. The surface tension between the clay and the subtle texture of the nonstick sheet helps them remain fully in contact as the clay dries, which helps to minimize warping. I find it works best if you tape the edges of the nonstick sheet to the work surface to keep it as smooth and flat as possible as the clay dries and shrinks. Let the top of the clay dry as much as possible before flipping over the piece to allow the reverse side to dry.
When choosing nonstick sheet, you can use the type made for lining food dehydrator trays, baking pans, or ovens, or the ones made specifically for craft use, as long as the sheets are very thin and the surface is very smooth. For example, Silpat and similar nonstick surfaces will leave a woven texture on the back of fresh clay. (Of course, you might like the texture for certain pieces!)
I recommend cutting large nonstick sheets into smaller squares or rectangles that make it easier to move or transport your pieces. I also cut some of my nonstick sheet into circles and squares to fit into the flat heating surfaces of my two cup warmers, which I sometimes use for very small, fairly thin pieces, such as charms or small components.
Using an Electric Cup Warmer or Hotplate
If you need to dry a metal clay piece quickly—especially something flat, small, and fairly thin—you can place it on a piece of nonstick sheet on an electric cup warmer (also called a mug warmer or candle warmer) or a hotplate. However, because the surface of the clay touching the warmer will dry very quickly, you'll need to turn the piece over every minute or two, at least for the first 5 minutes or so, to try to heat both sides as evenly as possible to minimize warping or cracking. The reason clay tends to warp when dried on a cup warmer is that the surface of the clay that is touching the heated surface dries quickly and shrinks (because the moisture has been driven out and evaporated by the heat and the metal and binder particles are compacted. The rest of the clay (especially if it is thick) hasn't yet dried and shrunk. Visualize a clay slab, and then imagine what would happen if just the bottom surface shrank: the clay that had not yet shrunk (or shrunk as much as the bottom) would start to dome slightly, i.e., warp.
For flat pieces, after you heat the first side for a minute (which will firm up the surface of that side enough to protect the texture), flip it over with a flat metal spatula and press the spatula against the piece for 5 to 10 seconds to keep the piece flat while the other side firms up. Continue to flip and press about once per minute until the clay is dry all the way through to the center. The amount of time will depend primarily on the thickness of the clay.
When you think the clay is thoroughly dry, move the piece from the warmer to a mirror and let it sit for between 5 and 20 seconds, depending on the thickness of the piece. Lift the clay and immediately check for any cloudiness on the mirror. If you see any cloudiness, it's condensation from moisture that's still in the clay, so dry the piece a while longer.
You can also allow the clay to cool completely and then hold it against your chin. If it feels cool, it isn't dry all the way through.
Note: These tests are not infallible, especially for thick pieces, but they do provide a helpful indicator. When in doubt, dry your piece longer than you think you need to!
Combining Drying Methods: The Best of All Worlds
As I explained at the beginning of this article, choosing a drying method for metal clay involves a trade-off between drying a piece quickly and drying it evenly. However, in some cases, using a combination of drying methods can help you strike a balance between speed and drying evenness.
For example, you might start by air drying the clay (on a piece of foam sheet or stainless steel mesh, or in a dehydrator or drying box) until the entire piece is mostly dry, then move it to an electric hotplate or cup warmer to drive out any remaining moisture.
Tip: Even if you have air dried your piece until you think it's thoroughly dry, it's good insurance to place it on an electric cup warmer for a minute or two (or longer, for thick pieces), just as extra insurance against possible warping, blisters or craters developing during firing.
Questions & Answers
Roughly how long does metal clay take to air dry?
It depends on a combination of factors, such as how moist the clay is, how thick the clay is, how large your piece is, how much lubricant you used, how dry or humid the environment is, the temperature of the room in which you are drying your piece, how porous or solid the drying surface is, etc.Helpful 4
My kiln isn't ready yet but I have all my tools and I am eager to start making something. Can I make a piece out of flex clay and leave it to dry for more than a week before firing it?
Yes, once you have finished your piece and it is ready to be fired, you can set it aside for a long time before firing it. While I haven’t done this with flex clay specifically, I have made pieces with PMC fine silver clay that I fired successfully more than a year later.Helpful 6
How long should PMC dry in a food dehydrator?
It depends on how thick, long and wide your clay piece is. A thin, small charm might only need 30 minutes, whereas a thicker, larger piece might need an hour or even two. A good way to determine whether your piece is thoroughly dry is to use the mirror test I described in this article.Helpful 3
© 2010 Margaret Schindel