Reconstituting Dry Metal Clay

Most of the methods for reconstituting dried metal clay involve chopping, crushing or grinding the clay before rehydrating it. There are various tools to help you accomplish this. Regardless of which tool(s) you choose, make sure to use them only for this purpose! Also, I strongly recommend using a a particulate respirator rated for dust (or at least a dust mask) to protect your lungs from breathing the metal clay dust as it's stirred up into the air.

My favorite tool for pulverizing dried metal clay is an electric grinder for coffee beans or spices - the kind that grinds the contents inside an enclosed compartment. It's fast, efficient, and it prevents the fine metal clay dust from dispersing into the air as it's being ground. Sometimes you can find these grinders at yard sales or thrift stores, and eBay always has them.

• Tip: Shaking the grinder as it's running will help to get all the little bits of clay into the blades. After you turn off the grinder, tap it smartly on your work surface to get most of the clay dust to settle into the bottom of the compartment.

You also can use a mortar and pestle to grind your dried clay. (If you do, I recommend tenting the mortar and pestle with plastic wrap as you work to keep the metal clay dust as contained as possible.) Be aware that using a mortar and pestle can be a bit hard on the palm of the hand that's holding the pestle (i.e., the grinding stick)..

You can use a rigid stainless steel clay blade to chop larger pieces of dried clay into small bits, which can be reconstituted as is. However, especially if you aren't patient enough to let all the water absorb fully into the binder, these chopped bits can result in lumpy clay.

To avoid those small lumps, you can grind the chopped clay bits with a mortar and pestle (chopping the clay first makes the grinding much easier!), or you can place them inside a heavy plastic bag, such as a freezer bag and crush the bits into a powder with a heavy rolling pin (or a similar substitute, such as an unopened bottle of wine).

Metal clay sanding dust may contain tiny amounts of abrasive grit from sanding pads, sponges or sticks, sandpaper or salon boards (especially very inexpensive, inferior quality sandpaper or salon boards). If you have a pet that sheds, you might end up with a few pet hairs or other debris that needs to be removed. And there are other types of debris that can end up in your metal clay dust or scraps.

If you suspect that there may be any type of grit , pet hair, or other debris in the dried clay or dust you want to reconstitute, it's a good idea to grind all the clay you are reconstituting into a fine powder and then strain or sift it through a piece of stainless steel mesh (such as an 80-mesh enamel sifter) or coarsely-woven nylon material before rehydrating it.

To protect yourself from breathing in metal clay dust, consider taking the following precautions:

• Wear a dust mask at a minimum, or preferably a particulate respirator.
• Grind you clay in an electric coffee or spice grinder to keep the clay dust from dispersing into the air.
• Read the section of this lens on Chopping, Crushing or Grinding Dried Metal Clay.
• After the clay has been ground into a powder, tap the grinder on a table or countertop and let the dust settle before opening it.
• Consider place your hands, the clay dust, the sifting screen, and the collection container inside a large, gallon-size plastic bag (or tenting your hands and what you're working with with a large sheet of plastic wrap) while sifting the clay to help minimize the dispersion of the dust into the air.
• If you will not be reconstituting the clay immediately, cover the container tightly until you're ready to reconstitute the clay dust.

The following method takes a bit longer than the others I'll describe, but I find that it produces a perfect working consistency reliably.

• Start by grinding your clay into a fine powder, using any of the methods described under Chopping, Crushing or Grinding Dried Metal Clay.
• Strain or sift the clay dust into a small bowl or onto a piece of clean glass (see Removing Debris Before Reconstituting Your Clay).
  • Note: While this step is optional, it's a good idea even if there isn't any debris in your clay, because it will separate out any bits of dried clay that weren't pulverized, and it also aerates the clay dust a bit so that it's easier for the moisture to reach the binder.
• Still wearing the particulate respirator or dust mask you put on while grinding and sifting the clay, hold a mister bottle filled with water about 8" to 12" above the metal clay dust, aim it at the clay, and pump just one or two light spritzes of water (no more than that!), so that the mist of water settles down gently onto the clay dust. (This prevents the pressure from the spray from blowing the dust around.)
  You can use a pipette to add a drop or two of water instead of misting it, but a mister will distribute the water throughout the dust much more evenly.
• Using a small stainless steel spatula (I find that plastic spatulas break too easily when used for this purpose), gently mix the water into the clay, using a folding motion (as you would to mix flour or beaten egg whites into a cake batter).
  Important: Fold the moisture into the clay dust slowly and gently to avoid dispersing the clay dust into the air any more than necessary.
• Mash the moisture into the clay powder with the spatula to help the binder absorb it as much as possible.
• Spray on another light mist of water from time to time (always from a height, as before), stirring and mashing the moisture into the clay dust as much as possible before adding more water. The key is to be patient and take your time, adding only small amounts of water stirring and mashing in each new addition before adding more water! This will make it easier for the binder to absorb the water evenly, and will help reactivate the binder.
  • Adding too much water at a time also will create slip, making it harder to get all of it out of the bowl or off the glass and back into the mass of clay.
• Continue the misting, stirring and mashing cycle until the clay starts to pull together in little clumps.
• Add only one or possibly two more spritzes of water and then just keep mashing in the moisture patiently.
• As soon as the clumps start to pull together into a more cohesive mass, stop adding water!
  The clay still will look too dry at this point, but it's okay - I promise!
• Scrape the clay onto a piece of Freeze-tite (a heavy plastic wrap designed to protect food from freezer burn), or inside a gallon-sized, thick plastic food storage bag intended for freezing food, or onto two stacked sheets of regular plastic wrap, the heaviest thickness you can find. (Don't use Glad Press'n Seal®, because the clay will stick to the adhesive side of the plastic.).
• Either knead the clay very thoroughly inside the plastic bag or wrap, or, better yet, roll it out as thinly as possible inside the plastic, which will force the water into the binder evenly throughout the clay. (Thanks to Lisa Cain of the Mid Cornwall School of Jewellery for this fantastic tip!)
• Fold or roll the clay and press it firmly into a compact patty ball inside the plastic.
  • Another great tip from Lisa: If the clay still seems too dry, roll it out again inside the plastic as thinly as possible (to maximize the surface area) and spritz it lightly with water. Fold the clay over to trap the water inside, and then re-roll it inside the plastic to press the moisture into the binder.
• Wrap the rehydrated clay tightly in plastic and let it rest for least 30 minutes (and preferably overnight).
• Optional: Knead the clay again briefly through the plastic just before using it.

Be sure to watch Lisa's wonderful video demonstration of this method below!

...this method is for you.

If you have a lump of dried clay and you're not in a hurry to reconstitute it, there's no need to spend time grinding, grating or chopping it into small pieces. Just put the dried clay it into a sealed container or zippered plastic sandwich bag with some water and set it aside for a day or two (or three, depending on the size and amount of clay you're reconstituting). From time to time, stir, mash, or knead in the water to the best of your ability, and then seal up the mixture and set it aside again. Repeat this cycle until all the water is absorbed into the clay. If the reconstituted clay is too dry, knead in a little more water and set it aside to rest, preferably overnight.

To make it a bit easier for the water to penetrate and be absorbed, you can drill a few holes into the lump of dried clay, if you want to. But if you're willing to be patient, it isn't necessary.

There are several factors that can affect the consistency of reconstituted clay adversely:

• If the dry clay is very old, the binder may have degraded somewhat.
• The clay may have been contaminated with too much olive oil, Badger® Balm, or other clay release agent.
• If you used a cream, balm or lotion containing petroleum or petroleum derivatives (petroleum jelly, for example) on your hands, tools, or textures, it will contaminate the clay (and will not burn out cleanly in the kiln).
• If you apply a skin shielding lotion (such as Gloves in a Bottle™) to your hands but don't let it dry before touching the clay, it can contaminate the clay.

If your reconstituted clay doesn't have the same consistency as clay straight from the package, you can mix in one of the following additives, which may improve the clay's consistency:

• I and many other metal clay artists routinely add some new, fresh clay straight from the package to each batch of reconstituted clay (generally a 50/50 mix of fresh to reconstituted clay). This adds some fresh binder and also dilutes the proportion of any contaminants in the clay.
• Kneading in a few drops of lavender oil can improve the clay's workability.
• Another option is to mix in a very small amount of glycerin, preferably diluted with water (1 part glycerin to 3 parts water).
  • Note: If you add too much glycerin, the clay will remain flexible even after it dries, which will make it difficult to sand or file cleanly. The clay also may become crumbly.
• Some artists add in a small amount of CMC (carboxymethyl cellulose, also known as cellulose gum). a plant-based starch used in the food industry as a thickener. Many people believe that CMC (or a similar cellulose-based starch) is one of the organic binders used in commercial metal clay formulas. Adding a little CMC to reconstituted clay can serve to replace some of the degraded binder.
  • It's important to note that if you add more binder to the clay, it will shrink more based on the higher proportion of binder to metal particles.
  Note: I have not yet found any specific directions or proportions for adding CMC to reconstituted metal clay. If you have used this method successfully, please share your experiences in the Comments section of this lens. Thanks!

Once you've kneaded any of these additives thoroughly into your reconstituted metal clay, set the clay aside in a storage container that will keep it moist (see my Metal Clay Storage lens) for at least 30 minutes, and preferably a day or two. This will allow the additives to be absorbed into the clay completely. Then knead the clay well before using it.