Wedging Clay
(Video Demo at Bottom of Page)
First Step in Clay Preparation
One of the most important steps in working with clay is to prepare the clay before throwing or hand building. Wedging clay should always be worked on a plaster or canvas surface. It is usually easier if you are standing. I use a wedging table I made of plaster and covered with canvas.
If you have some clay you need to reuse the clay can be placed on the wedging table so that the plaster can absorb some of the moisture from the clay so it will be the correct moisture content prior to wedging.
I purchase my clay already prepared and wedged for me. However, if I use some clay and it doesn’t turn out the way I think it should, I wedge it a little and put it in a plastic bag, set it aside for a couple days and then wedge it up to get the air bubbles out again.
Always start with wedged clay so all the bubbles are out. First take some clay and slam it onto the wedging table. Then cut it with a wire cutter in half and throw one piece down on top of it in the same direction. Repeat this over and over again until you don’t see any more bubbles in the clay.
By repeating this step over and over again, it is wedging the molecules of the clay, nice and tight together and eliminating as many bubbles as possible.
Even though you have wedged the clay according to the above step until you don’t see any bubbles you still need to wedge again by using the cone method.
I like to weigh the clay before I begin to wedge. I use different weights of clay for lids, bowls, vases and other items. If I weigh my clay prior to wedging I have a record of what size pot or lid the clay will be when I finish throwing it on the potters wheel.
It is very important that you keep records of the weight of your clay. If you have a record to refer back to, when you are ready to make a mug you know exactly what the weight of the clay needs to be to obtain the size mug you want to make.
Before I get started making a piece of pottery on the wheel, I plan what type of pot I will be making. Is my finished pot going to be a mug, bowl, vase, lamp or platter?
Based on the item, and what the dimensions are going to be, I decide the weight of the clay I want to wedge for that item. Once I have determined what size pot I want to make, I weigh the clay on a food scale.
In the beginning sometimes you just need to guess at the weight of the clay you will need to make a certain item. If you are unsure, try throwing some pots using clay of different weights using 1/2 pound increased increments so you become familiar with the different sizes that the different weights of clay will produce according to your style of throwing.
This is due to the fact that each potter will have an individual style and thickness to their throwing so the size of the finished pot can vary for the weight of clay used.
You always need to keep in mind that as your pot dries it will shrink in size. It will also shrink in the bisque firing, which is the first firing. The bisque fire helps to eliminate the extra moisture in the pot and is fired to 1890 degrees. The pot will also shrink even more in the final firing. The hottest temperature is in the last firing, often called the final firing; the more the pot will shrink.
When purchasing clay from a company that is processed and ready for use it will usually state the shrinkage rate for each particular clay body. Therefore, you must remember to make the pot just a little larger than the desired finished size.
I usually start with ¾ pound of clay for a mug. Many times I will use three pounds of clay for an average size bowl. Three pounds of clay will also make a nice size vase.
A little planning, weighing, and wedging will go a long way in helping you to consistently achieve a successful piece of pottery.
Wedging Clay--Cone Method
Cone wedging clay is accomplished by using a kneading action. With your right hand on the right side of the clay and your left hand lower and close to the table. Push downward and away from you.
You will be working mostly with your right hand. The clay will move back away from you just a little bit and leave some clay coming from the right side of the cone.
Using
your left hand, rock the clay back toward you, so that it is standing on the one
or two inch tail of clay left after the first step. Apply just a little bit of
rightward and downward pressure with the left hand as you bring the clay back.
The
pressure you use should be less than what your right hand had just applied to
the clay. As your left hand rolls the clay onto its tail and compresses down and
to the right, the original tip of the cone will drift to the left and the tail
should fold up under the cone.
These steps need to be repeated anywhere from 15 to 25 times until the clay is totally homogeneous and there are no more bubbles. You will be able to see how the clay is folding itself inwardly with the kneading action.
When you
are finished you can
see how it shows the spiral at the butt end of the cone.
I like to have the cone as balanced as possible all the way around to speed up the centering process when placing it on the pottery wheel. I continually pat the clay with the palm of my hand around the butt end of the cone to accomplish this.
By acquiring a cone shape during this process, it will help to compact the bottom of your pot when it is placed onto the pottery wheel head, which will help to avoid the cracking of the pot bottom during the firing process.
Wedging the clay helps to make sure that the clay is homogeneous in stiffness and does not have any air pockets. When there are bubbles in your clay, it can trap the air, and while throwing the pot, it will cause the clay to go off center.
If the pot is thrown off center it will hinder the success of the piece of pottery you are making, and can cause your pot to blow up in the kiln due to the air expanding during the firing process.
Once you are finished wedging the clay it is ready for use on the potters wheel for a thrown piece of pottery, or you can roll it into a slab for hand building a piece of pottery.
Whether throwing or hand you will be sure to have good results if the clay is properly wedged before you begin project!
Watch the video of this step of the pottery making process. It is a lot easier to understand if you watch it being done rather than reading about how to do it!