Wedging is a process of blending the clay together to create a consistent clay body to work with. It also removes air bubbles from within the clay. Inconsistent clay and air bubbles can both be problematic when creating sculptural objects or pottery with clay. Wedging is an important process for all potters, as it will need to be done often in the clay studio. Through wedging the artist manipulates the clay in order to improve its overall quality to prepare the clay for use in handbuilding or machine assisted techniques. Failure to wedge clay thoroughly will often result in weak pieces that may not make it through building, throwing, drying or firing process or are likely to have imperfections or break easily.
Wedging clay serves 2 main purposes
Creating a CONSISTENT clay body
Removing AIR BUBBLES
Through the wedging process the pressing, compressing, and/or slamming of the clay aligns the platelet particles of the clay on a microscopic level which actually makes the clay more workable and strong, and consistent for throwing on the wheel. Isn't that so neat... I'm geeking out here!
There are a few different methods for wedging clay including...
Stack & Slam
Rams Head
Spiral or Seashell
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Clay Mixer - (Machine Assisted) - A clay mixer is designed to mix / blend clay thoroughly and can be used to mix clay of various types and stages.
Pug Mill - (Machine Assisted) - A pug mill is a machine that blends & de-airs clay mechanically so that it is workable. Essentially it is a machine that wedges clay.
The video to the left provides a brief overview of each of these methods. Please note the presenter does NOT fully wedge the clay in these videos!!! You will learn more about each of the hand wedging techniques listed above in the sections below, as well as in class. After viewing and learning each technique, you will then be able to learn and apply the method/s that work best for you in any given situation. Let's learn how to wedge! It can be so therapeutic and satisfying to watch, learn and practice these methods! (That is after you get through the frustration of persevering through practicing how to do it properly!)
This is a great video in which a teacher discusses the importance of wedging clay, her wedging setup in her classroom, and demonstrates both the rams head & spiral method of wedging. She gives great tips on wedging, and shows some issues students may have when attempting these techniques.
So the big question is WHEN does clay actually need to be wedged?
NEW OR PURCHASED wet / plastic clay -Depends... Sculptural... No Need To Wedge - If clay is purchased as "wet or plastic" it generally does not need to be wedged before beginning a project. New clay can be cut off the block and used as is. The term "cut off the block" describes how wet clay is usually packaged in 25 lb or 50 lb blocks or cubes of clay and wrapped in plastic to keep the moisture in. It comes ready to use, and should already be pre-wedged and workable as long as it hasn't sat around too long and begun to harden. Wheel Throwing... Wedge - Many Potters who throw on the wheel still wedge new or even pugged clay to align the clay platelets and ensure that the clay is thoroughly blended and prepared to be wheel thrown.
USED wet / plastic clay - Nearly Always Needs Wedged - This describes clay that has been either set out, or worked with, or cut off or separated from a block or chunk of clay from a previous project While working with clay using a variety of techniques it is not uncommon to need to pinch off, carve out, and trim clay pieces. This leads to excess clay that is often piled up, smooshed together, balled or cubed. Before reusing this clay on another project it is important to wedge the clay together in order to blend together the separated pieces of clay, as well as the variations of harder or softer clay that may be incorporated. It will also remove the air bubbles trapped between the various pieces of clay. (NOTE: In our class we usually try to keep extra clay pieces separated in bags by softness or hardness to make the wedging process more efficient.) The only exception needed to wedge clay that had been set aside from a previous project is that if the clay had already been wedged, and only cut or tore from the previously wedged block of clay and stored to lock in moisture.
RECYCLED wet clay - Always Needs Wedged - Clay that has been recycled or re-constituted will always need to be wedged. The process of recycling clay usually includes rehydrating clay pieces of various sizes, shapes and dehydration stages. The clay is not completely broken down when reconstituted with water and will therefore be inconsistent in texture and hydration throughout. Thus, wedging is extremely important to blend the clay thoroughly before using.
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POWDERED CLAY - Depends - Hand mixed powdered clay, or even clay mixed with a cement drill will Eventually Need Wedged - Powdered clay is dry it cannot be wedged until it has been mixed with water and any other desired additives. Many artists use a hand drill with a cement mixer attachment to mix powdered clay, by starting with water and then adding clay little by little much like adding flour to a wet mixture in baking. This creates a slurry, that once it has been mixed and set out to harden slightly it will need to be thoroughly wedged. However, if using a clay mixer, or a pug mill proper, the powdered clay, once mixed or pugged is ready to use, but many potters still prefer to wedge their mixed or pugged clay.
DRY CLAY - Cannot Be Wedged - ... At least until it has been rehydrated, reconstituted, and/or recycled
Clay chuncks that have been compressed into a cube shape, and then cut diagonally with a wire to form two clay "wedges"
Slam one wedge onto the tabletop, and thent slam the other wedge directly on top of the first. The action forces air from the clay. Note the open air pocket. Source: Claywork, Form & Idea in Ceramic Design - 3rd Edition - Leon I. Nigrosh1995
It is my understanding the following method is actually where the term "wedging" comes from. For our purposes her I will call it the "True Wedge", although that is not a common term, as this process has somewhat evolved into the stack & slam. It is important to note that this process is typically applied as a starter method prior to using one of the other forms of wedging the clay. If you look at the picture to the left you can easily see the "wedge" shape cut from a cube of clay. The cube was created from chunks of clay that have been "smoooooshed" together and then pounded or slammed into a block shape.
So... here's how to "True Wedge"... with the main purpose of de-airing
Gather the various clay bits and chunks you want to use and ...
Compress or Smooooooosh them all together into one large chunk
Then slam that mass on the table, rotating directions each time in order to form a cube
Next cut the cube diagonally so that you have two (or more) wedges
Then you slam the wedge on the table or wedging surface forcing the air out
Repeat as needed
Follow with one of the other "wedging" techniques below
OVERVIEW - Ram's head wedging gets its name from the way that the clay chunk tends to resemble a rams head during the wedgin process
BENEFITS
Probably the easiest method to learn and become efficient using
Works well with medium to small chunks of clay
This will most likely be the method that you are using in class
DRAWBACKS
Can be harder on the wrists over time.
Requires more core and/or upper body strength if wedging large pieces.
OVERVIEW - Spiral wedging also gets its name from the way that the clay chunk resembles a spiral seashell during the wedging process. Some artists when they spiral wedge form the clay into a conical or cone like shape, while others wedged clay end up in more of a round thick basin- like form with a sort of cone like or ball like mass, that and then be worked back into a cone shape.
BENEFITS
Once this technique is mastered, it is a fast, very efficient method of wedging
Works well with large chunks of clay
DRAWBACKS
More difficult or time consuming to learn
If wedging very large pieces, it requires more effort and core or upper body strength (can be a workout!)
OVERVIEW - The "stack & slam" method also known as "cut wedging" or "wire wedging" is a method in which one piece of clay is slammed down onto another in order to align the clay platelets directionally and blend the clay.
BENEFITS
Easy on the wrists
Good for blending clay at different hardness/softness stages
Great for blending different clay bodies together
DRAWBACKS
Must align or "stack" clay properly or "directionally" in order to truly blend the clay
Can take a long time to thoroughly blend clay
Need a very sturdy designated wedging surface that can handling
In the video to the left the artist mixed blue dye into her clay so that you can see the clay truly start to blend together during the wedging process for each of the three methods, "Ram's Head", "Spiral", & "Stack & Slam". She compares each method by counting the number of repetitions to determine which is fastest. However. it is important to note that fastest isn't necessarily best, and also, as every artist is different what is most efficient for one person or particular size of clay might actually be slower or less efficient for another person or variation of clay. Most artists have their preferences. While some always use the same method of wedging, others use different methods for various projects.
This artists, is sort of silly when describing both the ram's head and spiral method of wedging. What I like about this video is that he discusses how he uses the ram's head method as a professional, which is often considered the easiest or a beginners method of wedging.