How Do You Bond Clay Together?

Clay is a type of fine-grained natural soil composed primarily of minerals like silica and alumina. When moistened and kneaded, clay becomes malleable and can be molded into shapes which will hold their form when dried. This unique property makes clay a versatile material used for a wide array of applications including pottery, sculpture, bricks, and tiles.

However, clay’s plasticity also presents challenges. Because untreated clay remains brittle after drying, methods to bond and strengthen clay are needed for it to be a functional material. By properly joining clay components, artists and builders can construct durable ceramic objects, structures, and artworks. The process of adhering clay is therefore fundamental to unlocking its creative potential.

Table of Contents

Slip

Slip is a liquid mixture of clay and water that acts as a glue to bond pieces of unfired clay together. Using slip is one of the most common methods for joining clay.

To make slip, simply mix together some of the clay body you are using with enough water to create a liquid with a creamy consistency. The slip should be thick enough to bond to the clay, but thin enough to spread smoothly into the joint. A good starting ratio is 1 part dry clay to 4 parts water.

The advantage of using slip to bond clay is that it creates a very strong seamless join. Since the slip is made from the same clay body it blends perfectly. Using slip also allows you to fill any gaps and smooth over rough areas where two pieces of clay meet. It’s an easy, inexpensive method for joining.

The downside is that applying slip and pressing the clay pieces together takes some practice. Too little slip and the bond will be weak. Too much slip will make the join messy. Slip can also add moisture where you don’t want it, which may require extra drying time.

To join clay with slip:

Score or roughen the surfaces to be joined. This gives the slip something to grab onto.
Apply slip generously to both surfaces using a small brush, sponge, or your finger.
Press the clay surfaces together firmly. Wipe away any excess slip.
Allow the slip to dry slightly before handling.

Use Water as an Adhesive

One of the simplest ways to bond clay pieces together is by using water. This method involves scoring or roughening the surfaces to be joined, then applying water along the seam. As the water seeps into the clay, it temporarily softens the material so the pieces meld together as they dry.

The main benefits of using water are that it’s readily available and easy to apply. There’s no need to purchase special adhesives. Water also dries quickly without altering the color or texture of the clay. The bond is quite strong, especially on pieces that will be fired in a kiln.

On the downside, moisture can lead to cracking as the clay dries and shrinks. The water method may not work as well for bonding unfired pieces or items that will be outdoors. Weight and stress can cause seams bonded with water to separate over time.

To use water, first score or scratch the surfaces to be joined. This roughs up the clay so the pieces interlock better. Apply water along the seam using a small brush or spray bottle. Press the pieces together firmly and let dry completely. For stronger bonds, slip can be used instead of plain water. Slip provides more clay content to fill in pores and gaps between the pieces.

Scoring and Slipping

Scoring and slipping is a common method for joining clay together. It involves scoring or scratching the surfaces to be joined, applying water or “slip” to the scored areas, and then pressing the pieces together.

To score the clay, use a serrated rib or knife to scratch diagonal lines across the surface. These lines should be close together to maximize the scratched area. Score both pieces that you want to join.

After scoring, wet your finger and smooth a layer of slip over the scored areas. The slip can also be applied with a small brush. Use a clay mixing water or diluted clay mixture for the slip.

Finally, firmly press the two scored and slipped surfaces together, wiggling slightly to close any gaps. Smooth over the seam with a wet finger or tool. Allow to dry completely.

The pros of scoring and slipping are that it creates a strong mechanical and chemical bond between clay pieces. No additional materials are required beyond water and clay. It is an easy technique to learn. Scoring and slipping has some limitations on very large clay pieces or certain forms.

The scored lines give the slip more surface area to adhere to. The water combines the clay particles for a tighter bond. When done properly, scored and slipped seams are very durable.

Clay Slurry

The clay slurry method involves making a thin mixture of water and clay, then brushing or pouring it onto the seam where two pieces of unfired clay meet. The water helps the clay bond together, fusing the pieces as the slurry dries.

Some of the pros of using a clay slurry are that it creates a very strong bond and is made of the same material you are joining. It blends in seamlessly with no trace of glue or fasteners. A clay slurry can fill any gaps between pieces and is excellent for smoothing edges. It’s also very accessible and affordable since it uses clay and water you likely already have on hand.

In terms of cons, clay slurry takes time to dry and bond fully before the piece can be handled. It may shrink slightly as it dries. The bond may not hold up over time as well as other methods for structural or heavy pieces. Using a clay slurry takes precision and care to apply smoothly and cleanly.

To use the clay slurry method:

Mix clay and water to a thin, smooth consistency in a small container.
Apply the slurry along the seam using a soft brush, sponge, or by pouring.
Let the seam dry completely before handling the piece.
Once dry, smooth away any dried excess or unevenness with a damp sponge.

With some practice, clay slurry can create an invisible, lasting bond between clay pieces. It’s an accessible option worth trying for most clay projects.

Glue

Glue is another way to securely bond clay pieces together. Many types of glue will work with polymer and air-dry clays. White glue, super glue, epoxy glue, and silicone glue are commonly used.

To use glue:

Make sure the clay surfaces you want to join are clean and free of dust.
Apply a thin layer of glue to one or both surfaces.
Press the surfaces together firmly and hold for 30-60 seconds.
Allow the glue to dry as directed on the product label before handling.

The pros of using glue are that it creates a strong, permanent bond and dries clear. Glue can fill small gaps between clay pieces. Most glues are inexpensive and readily available.

The downsides are that glue takes time to dry and the pieces must be held together while drying. Some glues can leave behind shiny spots on the clay surface. Glue may not work well for large surface areas.

Mechanical Fasteners

Mechanical fasteners provide a way to physically hold clay pieces together. Some common options include:

Toothpicks or skewers – These can be inserted into two pieces of clay to hold them together. Make sure they are completely covered by the clay.
Wire – Thin wire can be threaded through holes in the clay and twisted together on the inside to hold pieces together. Like toothpicks, the wire should be completely encased in clay.
Nails – Small nails can be hammered through overlapped areas of clay. The nails should go all the way through both pieces of clay for the strongest hold.

Pros of using mechanical fasteners:

Provides very strong, rigid connections between clay pieces.
Useful when the clay needs extra reinforcement and support.
Can create interesting sculptural effects by leaving parts of the fasteners exposed.

Cons:

Can weaken and crack the clay if too much force is used to insert them.
Visible holes, marks, or cracks may show up where they penetrate the clay.
Adding fasteners takes more time and effort.

To use mechanical fasteners:

Make holes, slots, or channels in the clay pieces where you want them joined.
Insert the fasteners through the holes so they penetrate both pieces of clay.
Make sure the fasteners are completely seated in the clay.
Bend, twist, or hammer the ends of the fasteners to hold everything tightly together.
Cover any exposed parts of the fasteners with additional clay if desired.

Choosing a Method

When deciding how to bond clay pieces together, consider the pros and cons of each method as well as the characteristics of your particular project. Here are some factors to keep in mind:

Size of project – For smaller pieces, water or slip may be the easiest method. For larger sculptures, mechanical fasteners may provide more support.
Firing requirements – Some methods like glue or certain fasteners may not hold up when fired. Choose slip or scoring if planning to fire the piece.
Permanence – Do you need a temporary bond or long-lasting connection? Slip and scoring create strong permanent bonds while water or tape can allow for later separation.
Visibility – Will the join be visible or hidden? Opt for neater options like slip on exposed areas. Mechanical fasteners can work for hidden joints.
Ease of use – Beginners may want to start with water or tape. Slip and scoring take practice to perfect.
Strength – Assess the stress on joints and size of bonded pieces. Slip/scoring or fasteners provide the most durable bonds for heavy sculptures.
Aesthetics – Choose adhesives for inconspicuous bonds. Slip/scoring offers seamless connections. Fasteners can add design interest.

In summary, opt for slip and scoring when firing pieces and desiring strong, permanent connections. Use water or tape for temporary assembly. Pick glues for strength without firing. Add fasteners for large-scale projects and hidden structural support.

Troubleshooting

When bonding clay, you may encounter some common problems. Here are some troubleshooting tips for the most frequent issues:

Cracking Between Joined Pieces

If you notice cracking where two pieces of clay meet, there are a few possible causes. The clay may have dried out too much before bonding, or it may have shifted before the bond was fully set. Be sure to score and slip the clay surfaces while the clay is still moist. Allow plenty of drying time so the bond is fully hardened before moving the pieces.

Bond Falls Apart When Dry

If the clay pieces separate after drying, the bond likely did not have enough slip. Increase the amount of water in the slip mixture to fully saturate the scored surfaces. Ensure the slip coats the entire surface of both pieces for the strongest bond.

Uneven Bond Line

An uneven seam where two pieces meet indicates an improper scoring technique. Score lines should be parallel, evenly spaced, and uniform in depth. Score both clay surfaces thoroughly before applying slip for the smoothest bond.

Bond Failure After Firing

If pieces separate after firing, the clay may have been bonded at an incompatible moisture level. Only join leather-hard clay pieces, as the moisture content will be similar. Also ensure proper drying time before firing to fully cure the bond.

Conclusion

There are several effective methods for bonding clay pieces together to create beautiful and functional ceramic works. The most common techniques utilize slip, water, scoring and slipping, clay slurry, or glue to fuse the clay through molecular bonding. Mechanical fasteners like nails, wire, and staples can also join pieces together through physical restraints.

Choosing the right method depends on the type of clay, the pieces being joined, whether the work will be fired or remain unfixed, and the strength of the desired bond. With trial and error, ceramic artists discover which techniques work best for their creations.

As clay bonding methods continue to evolve, new adhesives and processes will emerge. However, the time-tested techniques like slip and scoring have proven reliable and accessible. With a basic understanding of these fundamental approaches, both novice and expert ceramicists can successfully bond clay in their artistic works.