What Is The Thickness Of The Clay Should Be When Making A Pinch Bowl?

What is a Pinch Bowl?

A pinch bowl is a type of pottery handmade by pinching the clay into shape, hence the name. Pinch bowls date back thousands of years, with examples found in ancient Mesopotamia, Egypt, Greece, Rome, and many other early civilizations. They are one of the most basic and primitive forms of pottery making.

To make a pinch bowl, a lump of clay is pressed between the fingers and palm to hollow out the center and shape the exterior. No wheel or mold is used – just the artist’s hands. Pinch bowls can range from small, simple finger bowls to larger decorative pieces.

Today, pinch bowls are commonly used as a beginner project in pottery and ceramic arts classes. They help teach the fundamentals of working with clay. Pinch bowls are also a popular craft activity for children. The simple, hands-on process allows kids to make pottery without requiring throwing skills.

In addition to educational uses, pinch bowls serve a variety of decorative and functional purposes. Small pinch bowls often hold trinkets, jewelry, keys, or coins. Larger bowls can display flowers, hold fruit, or serve food. Contemporary artists also create conceptual art pinch bowls as wall hangings and sculpture. The organic, freeform shapes make pinch bowls a versatile art form.

Ideal Clay Properties for Pinch Bowls

The clay you select for making a pinch bowl is one of the most important factors that will determine the success of the project. Using clay with the ideal properties helps ensure the bowl holds its shape without cracking or falling apart.

The clay should be soft and pliable. If the clay is too firm or stiff, it will be very difficult to shape and smooth the bowl using only your fingers. The clay needs to gently bend and flex as you pinch and stretch it into shape.

Avoid using clay that feels overly wet or dry. Wet clay will droop and lose its form too easily. Clay that is too dry will crack and be prone to breaking. The moisture content should be just right – where the clay is workable but still maintains its form.

Make sure the clay has a smooth, consistent texture free of debris. Any rocks, twigs or hardened bits in the clay can poke holes in the bowl or make weak spots that lead to cracks. Carefully condition and wedge the clay thoroughly to create an evenly mixed and smooth ball of clay, ideal for pinching.

Determining the Right Thickness

The thickness of the clay is one of the most important considerations when making a pinch pot or bowl. The thickness affects both the strength and weight of the finished piece.

A typical thickness for a pinch bowl is usually between 1/4″ and 1/2″. Thinner walls under 1/4″ may be too fragile, while thicker walls over 1/2″ will make the bowl very heavy.

In general, thicker clay walls will provide more stability and durability for utilitarian-style pinch bowls meant for holding food or other items. Thinner walls may be suitable for decorative bowls not intended for heavy usage.

The intended size of the bowl is another factor. Large bowls will require thicker walls than smaller bowls for structural integrity. For very large pieces, thicker walls up to 3/4″ or 1″ may be advisable.

Beginners should start with a medium thickness around 1/3″ to 1/2″ until they get a feel for working the clay. The thickness can always be adjusted as you shape the bowl by pinching in or out as needed.

Taking the time to determine the optimal starting thickness for your particular pinch bowl project will provide the right balance of stability and weight in the finished piece.

Starting the Pinch Bowl

Once you have your ball of clay ready, it’s time to start shaping it into a bowl using the pinch pot technique. Begin by cupping the clay in your hands, with your fingers gently curved around the clay ball. Apply even pressure as you slowly rotate the clay, smoothing the surface and forming a natural hollow in the center. Take your time in the beginning to compress the clay and eliminate any air pockets or cracks on the surface.

As you pinch and rotate, the walls of the bowl will start taking shape. Use your thumbs to press into the center while your fingers press against the outside, elongating the form into a basic bowl shape. The clay should start feeling thinner between your hands at this point. Be careful not to pinch too hard or make the walls too thin yet; about 1/4 to 1/2 inch thickness is ideal for starting out.

Hollowing Out the Interior

Once you have the basic shape formed, it’s time to hollow out the inside of the pinch bowl. This step is important for creating an even thickness and preventing cracking during drying and firing. Use your thumbs to pinch and push into the center while slowly rotating the clay. Apply even pressure as you work to maintain uniform wall thickness.

Aim for approximately 1/4 inch thickness throughout the bowl walls and base. Leaving too thin of a wall risks cracking and makes the piece more fragile. However, avoid leaving too thick of a base as it may resist drying and be prone to exploding in the kiln. The interior space should feel hollow while still retaining enough clay for stability.

Work slowly and carefully, frequently stopping to check thickness. Pinching out the interior takes time and patience. If the walls start to feel too thin, gently push from the outside to add more clay. The key is gradually thinning the whole interior through intentional, controlled pinching and rotation. Once you achieve an even thickness, move on to shaping and refining the outside surface.

Shaping the Exterior

Once the interior of the pinch bowl has been hollowed out, it’s time to shape the exterior into a smooth, rounded form. Start by gently pinching and smoothing the sides of the bowl with your fingers. Apply even pressure as you work your way around the entire exterior surface. The goal is to eliminate any bumps, cracks, or irregularities in the clay wall.

As the form takes shape, you can begin using basic pottery tools to further refine the texture and appearance of the outside surface. A rib tool is ideal for compressing and smoothing the clay. Use broad, even strokes going in one direction around the bowl. You can also use loop tools to carve out any designs or patterns you want to incorporate. Take your time and work slowly to avoid tearing or distorting the clay.

Continue refining the shape and texture until you achieve a smooth, rounded, visually appealing exterior for your pinch bowl. The thickness of the walls should remain even all the way around. Keep the bottom slightly thicker and taper the thickness gradually up towards the rim. Having an appropriate clay thickness and smooth exterior will ensure your finished pinch bowl has a professional, artful look after firing.

Adding Decorative Elements

After the basic shape of your pinch bowl has been formed, you can add decorative elements to make it unique. Here are some ideas for decorating your pinch bowl:

Incise patterns, textures, or designs: Use wooden or metal tools to carve patterns directly into the surface of the leather-hard clay. Consider geometric patterns, textures like crosshatching, or freeform designs. Incising provides interesting visual elements and dimension.

Attach decorative elements like handles: Carefully attach handles, feet, or other sculptural elements to your bowl while the clay is still soft and wet. Use slip (liquid clay) to join the pieces. Decorative handles or feet can add whimsy and functionality.

Add color with slips or glazes: After bisque firing, use colored ceramic slips or glazes to coat the outside of the pinch bowl. The slips and glazes will melt and fuse to the clay during the final firing, adding vibrant colors. Try solid colors, gradients, or patterns.

The possibilities for decorating and personalizing a homemade pinch bowl are endless. Get creative with textures, attachments, patterns, colors, and more. Decorative elements take a plain pinch bowl to the next level of artistry and craftsmanship.

Drying the Pinch Bowl

After shaping your pinch bowl, it’s important to let it dry slowly and thoroughly before firing. If the clay dries too quickly, it can crack or warp. Here are some tips for proper drying:

Allow the bowl to air dry slowly at room temperature. Don’t place it in direct sunlight or near heating vents, as this can cause uneven drying. A gradual, ambient dry over 1-2 weeks is ideal.

Wrap the damp bowl loosely in plastic wrap or place it in a plastic bag that is open or has holes poked in it. This will slow down the drying so it happens at an even pace. Make sure not to wrap too tightly or the clay may stick to the plastic.

Let the pinch bowl dry for 1-2 weeks before doing any firing or bisque firing. The longer the drying time, the less chance there is of cracking or explosions from trapped moisture. Be patient and allow the clay to release its moisture completely.

When the bowl no longer feels cool, damp or sticky, it is ready for the kiln. Do a final check by weighing the bowl and comparing to its original wet weight. A substantial weight loss indicates the clay is thoroughly dried and ready to be fired.

Firing/Bisque Firing

Once the pinch bowl has dried completely, the next step is to fire it in a kiln. This first firing is called a bisque firing or biscuit firing. The purpose of bisque firing clay is to permanently harden the clay body through sintering, which fuses the clay particles together at a molecular level.

It’s important to fire the pinch bowl according to the manufacturer’s recommendations for the specific clay type used. These recommendations will provide the ideal temperature and ramp times to properly bisque fire the clay. Typically, cone 04-06 is an appropriate bisque temperature range for mid-fire clays used for handbuilding. Low-fire clays can be bisque fired at cone 018-04, while high-fire clays are usually bisque fired up to cone 6.

The clay must be completely bisque fired before applying glazes and doing a final firing. Bisque firing prepares the bare clay to accept glazes by creating a hard, porous surface for the glaze to adhere to. Firing glazes on unfired clay can cause cracking, peeling, or bubbling issues with the finished piece. Properly bisque firing is a crucial step for creating functional and durable pinch bowls.

Glazing and Final Firing

After the bisque firing, the pinch bowl is ready to be glazed and fired a final time. It’s important to choose a food-safe glaze if you intend on using the bowl for food purposes. Food-safe glazes do not contain lead or other toxic materials that could leach into food or drinks. Verify that the glaze specifies “food-safe” or has been tested for dining ware purposes.

Next, follow the firing instructions provided by the glaze manufacturer. Most glazes for stoneware clays are formulated for firing to cone 6, which is about 2,200°F. The glaze will melt and fuse to the clay body at this high temperature. Make sure your kiln can reach the proper cone for the glaze. The glaze should spread smoothly and evenly across the surface of the pinch bowl.

After the final glaze firing, the pinch bowl will be complete and ready to use. The glaze provides a glassy coating that is non-porous. This allows the bowl to hold liquids without leaking and makes it easy to clean. The bowl will be durable, hygienic, and attractive after the bisque and glaze firings.