Does Paper Clay Dry Hard?
What is Paper Clay?
Paper clay is a modeling and sculpting material made from a mixture of paper pulp and clay. The added paper gives clay more strength and flexibility compared to regular clay.
The basic ingredients of paper clay are clay and cellulose fiber, which is derived from plant-based paper. Most paper clay recipes also contain additives like glue or cornstarch to enhance the properties and workability of the material.
The cellulose fiber binds the clay particles together, allowing the clay to be rolled, shaped, and sculpted without becoming brittle as it dries. The paper pulp also makes the clay lighter in weight compared to regular modeling clays.
Paper Clay Origins
Paper clay was invented in the United States in the 1980s as an alternative to traditional clay that prevents cracking and tearing during the drying and firing process. Traditional clay often develop cracks as the water evaporates, due to the clay shrinking and warping. Paper clay was developed as a solution by adding cellulose fiber from materials like paper, cardboard, or sawdust to the clay body. The plant fibers act as a binder and reinforcement, holding the clay particles together and providing strength to limit shrinking and cracks.
The addition of paper makes the clay more durable and flexible as it dries. This allows paper clay artists and crafters to create ceramic pieces that are stronger and have fewer flaws caused by cracking and tearing. The plant fibers also make paper clay lightweight compared to pure clay. While the origins are uncertain, paper clay first emerged commercially in the US in the 1980s as an alternative to traditional pottery clays that enabled the creation of larger, stronger finished pieces.
Benefits of Paper Clay
Paper clay has several benefits that make it a popular choice for artists and crafters:
Paper clay doesn’t crack and shrink as much as regular clay as it dries. The cellulose fiber added to the clay gives paper clay more flexibility and strength. This makes it possible to create thinner and more delicate structures than with regular clay without having them warp or break as they dry.
The fiber also allows the clay to hold fine detail well. Paper clay is able to take and retain intricate designs without the details becoming distorted. This makes it an ideal material for items such as jewelry, miniatures, and decorative pieces that rely on fine or fragile elements.
In addition, paper clay achieves very high strength when fired. The end product is lightweight, strong, and slightly porous. Many clays expand when fired, but paper clay remains quite stable. This allows artists to create pieces that are thin-walled but sturdy. The finished clay has a texture similar to terra cotta.
How Paper Clay Dries
Paper clay dries through the process of water evaporation. The water in the clay mixture slowly evaporates over time, causing the clay to stiffen and harden. This is the same process that standard clay undergoes when drying.
However, the added paper fibers in paper clay assist with the drying process. As the clay loses moisture, the paper fibers bond together and give structural stability to the clay. The more the clay dries out, the tighter the paper bonds become, creating rigidity.
The drying time for paper clay depends on the thickness and size of the piece, as well as the climate. In general, paper clay dries much slower than regular clay. It can take days or weeks for paper clay to fully dry based on the thickness. Drying can be sped up by using fans, hair dryers or low heat, but air drying is most common.
Does Paper Clay Dry Hard?
Yes, paper clay does dry very hard. The clay component provides hardness as it dries. Paper fibers reinforce the clay as it hardens. When paper clay is formed and allowed to dry, the clay portion hardens as any regular clay would. The added cellulose fiber from paper binds with the clay as it dries, structurally reinforcing the material. This creates a very hard, durable compound that achieves bisque-like hardness when completely dry.
The paper component of paper clay undergoes a molecular change as the clay hardens around it. This essentially “locks” the paper into the clay matrix, preventing it from burning out in high firing temperatures that would incinerate plain paper. Tests have shown that once fully dry, paper clay can be remarkably strong and approach the hardness of ceramic bisqueware or terra cotta.
Paper clay achieves this drying hardness through a synergy between clay and cellulose fiber. The end result is a material much harder and more durable than air dry clays made without paper fiber additions. Items made from dried paper clay will maintain their strength and shape even if left unglazed. So for non-fired paper clay applications, the paper additive creates very hard, structural stability.
Paper Clay Strength
One of the biggest benefits of paper clay is its strength when dry. The combination of clay particles and tiny paper fibers makes paper clay extremely strong in its finished state, especially when used for thin pieces.
Paper clay has much higher dry strength compared to regular pottery clay. Pieces made with paper clay are less likely to crack or break, even when very thin. This makes it great for creating delicate sculptures, jewelry, ornaments and more.
However, paper clay’s high paper content also makes it prone to cracking if it dries out too quickly. Uneven drying can cause stress cracks. To prevent cracking, paper clay must be dried slowly and evenly. Wrapping projects in plastic while they dry helps retain moisture and prevent cracking.
So while paper clay’s strength when completely dry is excellent, care must be taken during the drying process. With proper drying techniques, paper clay will dry hard and maintain its strength through firing.
Preparing Paper Clay
Paper clay can be purchased ready-made from art supply stores, but many artists prefer to make their own mix at home. To make paper clay, you simply need to add shredded paper pulp to regular pottery clay. Typically, a mix of 50/50 paper pulp to clay is a good starting point. The exact ratio will depend on the type of clay used and personal preference. When mixing your own clay, it’s important to add the paper pulp gradually and knead it thoroughly to distribute it evenly throughout the clay body. Making paper clay does require some trial and error to find the right consistency and ratio of paper to clay that achieves the desired properties. The prepared clay should be smooth, pliable and have a texture similar to normal clay. It’s a good idea to test out a few small batches before mixing up larger amounts. Once the ideal paper to clay ratio is found, the clay can be wedged thoroughly and wrapped in plastic to store until needed.
Working with Paper Clay
Paper clay is a very versatile material that can be worked with in different stages of dryness. When paper clay is first mixed and is moist, it can be freely shaped, rolled, sculpted, carved, extruded, and joined. The paper pulp in the clay makes it strong enough in the moist stage to handle repeated shaping and manipulation without tearing or cracking.
Once paper clay starts to dry and becomes leather hard, the surface can be smoothed and refined by tools, fingers, or rubbing with a damp sponge. This is the stage where fine detailing and sculpting would occur. The clay still retains some moisture at this point so it can be shaped without cracking, but is stiff enough to hold intricate shapes and patterns.
It is important to let paper clay thoroughly dry before firing it. All moisture must be evaporated from the clay to prevent cracking or explosions in the kiln. The drying time depends on factors like the thickness of the clay and humidity, but can take days or weeks. Check the clay at the very center to ensure it is completely dry before firing.
Firing Paper Clay
When firing paper clay, it’s important to fire to the same temperature as the clay body used in the project. For example, if the clay body matures at cone 6, the paper clay piece should also be fired to cone 6. Firing to a lower temperature risks under-fired work.
Multiple thin firings are recommended when firing paper clay. Thin items, like tiles or sheets, may only require a single firing if they are thin enough. Thicker pieces should be fired multiple times, allowing the piece to cool completely between firings. This prevents bloating and cracking from built up steam.
Proper kiln venting is critical when firing paper clay. The paper fiber burns out between 500-600°F producing ash. The ash needs to be vented out of the kiln to prevent it from settling on the ware. Most kilns will require top, bottom, and side stoke holes opened to allow adequate airflow and venting.
Paper Clay Projects
Paper clay is an excellent choice for creating detailed sculptures and decorative pieces. The cellulose fiber gives paper clay high strength even when rolled thinly, making it ideal for sculpting delicate features. Paper clay holds details well compared to regular clay, allowing artists to create intricate designs.
While paper clay can be used for functional pottery, it is best suited for non-utilitarian works of art. Pieces made from paper clay are fragile and cannot withstand repeated high temperature firing. The fibers may also interfere with an ideal vitrified surface on functional wares.
The strength and workability of paper clay makes it a fun option for beginners to work with. Beginning sculptors can roll out thin sheets of paper clay to cut shapes and build forms without worry of tearing or collapse. The clay holds its shape as you sculpt without slumping or drooping before firing. Paper clay is also very light weight, reducing hand fatigue.
