Clay Expression
The Art & Craft of Expressing Passion with Clay
Seramik Kraftangan Malaysia, Kuala Lumpur, Selangor, PJ

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Magical Expression With Clay Ceramics Articles Contents
 
Why Do We Have To
"Wedge"?

Students often asked, “Why can’t we use the clay as it is; Why do we have to wedge it first?” It is not a must to wedge your clay before using -- IF you are willing to take a risk on the outcome of your masterpiece.

My first lesson in pottery was wedging and I was told that I had to wedge 200 counts per lump of clay and if I wanted to be sure I did it correctly I should do 300 counts! The following were the 3 reasons that drummed into me that taught me the importance of this seemingly uninteresting process:

The proper positioning of your body when wedging:

Place one leg in front and one leg behind.

Your palms should be positioned by the sides of the ball of clay that you are wedging.

The angle between your elbows and your wrist must form a 45˚ angle.

 

Tip of the Day

What is Rhythm?

Re-Centering your piece for trimming

One of the most difficult part of the trimming process is re-centering a piece on the potter’s wheel, especially when the piece is not 100% perfect.

There are many ways of re-centering a piece on the potter’s wheel but all of them require practice.

The one technique that I like to use is the tapping technique. With this technique all you have to do is place the piece of work on the wheel head like how you would normally do when you are about to start your centering process.

Now, instead of starting and stopping the wheel head to check if it is centred, keep the wheel moving at a constant and moderate speed.

You will have to use the tips of your right fingers to tap on the part (roughly 1.5cm) from the bottom of the piece that is sitting on the wheel head.

 
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1.
Wedging will remove the air pockets
in the clay. If there are air pockets in the clay, the piece will explode during the firing process. This is because when air is hot, it expands so it will force its way out of the small space that it is trapped in, hence  causing an explosion.
.
2.
Wedging is a way of mixing
the hard and soft spots found in clay. When hard and soft clay exists in the lump of clay that you throw, you will end up with a “wonky” piece. There will also be a chance of   cracks on the piece due to the uneven drying of the hard and soft spots on the piece.
.
3.
Through wedging
, you will be able to have a feel for the clay, to determine if it is very soft, hard, plastic, etc… this will guide you  on whether this clay is suitable for what you are about to make and how you should be making your piece. 

Let’s go a little deeper into understanding clay…. under the microscope the clay particles are plate-like in shape, and when pressure is applied to it, the particles arrange themselves in a 90 degree angle like a deck of cards. So when we wedge, we are actually arranging the particles in the clay. 

All the clay used in Clay Expression goes through a mixing processed clay mixer to make sure that hard and soft clay is properly mixed. Then the clay from the mixer is put through a machine (pug mill) to be de-aired and extruded. Thanks to this process, we no longer need to wedge 300 counts before we use our clay!

  Because the wheel head is spinning, by tapping on the piece, there will be an automatically draw of force that will bring the centre of your piece to align with the centre of the wheel head.

With this technique you will need to understand the tapping rhythm, so “what is the rhythm”?

When the wheel head is turning at a constant speed, the rim of the piece (part which we will trim) will also be turning consistently.

The rhythm we are referring to here is the speed of your fingers tapping on the piece.

If you are tapping at a beat of 1..2..1..2..1..2, you will be hitting the green spots and this would be ideal. We must also take into consideration that every time you finger hits the piece, it must exert the same degree of strength.

But if you are going at an irregular beat of 1….2..1..2..3……1…2, this means that you are actually hitting the lines in a non-systematic manner. Because of this, it would be very difficult for you to centre the piece.

With this tapping technique, you need to remember that the rhythm, the speed of the wheel and the strength you use to tap the piece, must all be consistent.

 

When the clay goes through VENCO Pug Mills, Australian made machine the particles in the clay arrange themselves accordingly...

But the problem are... only the particles on the outer ring of the extruded clay are arranged. The particles in the core of the extruded clay are still in a random, mixed arrangement. This therefore contributes to a different shrinkage rate between the outer ring and the core. As a result, cracks appear in our work.

What is a pugmill? A pug mill is used to blend clay to restore it to a more uniform workable consistency. This applies to new clay or clay scraps from previous work.

 

Clay is loaded into the feed hopper (closest to motor) and an internal auger pushes the clay along the barrel, through some fine screens before recompressing the clay and forcing it out the nozzle.
 

The de-airing models incorporate a vacuum pump -- (motor on the left of the pugmill) which removes air trapped within the clay while pugging is performed.

This produces the highest quality clay for immediate use on a potters wheel. 

So, to overcome this problem, wedging is necessary in order to change the arrangement of the particles and properly homogenize the clay particles before we use the clay. Proper wedging is the first step to a successful art piece! 

Wedge and Rhythm Article by: Cindy Koh
Bs. in Arts (Ceramics) & Associate studies in Business
Administration University of Evansville, Indiana, USA 1995

 

 

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