Ceramic Life- Chapter One- Producing a Slip-cast Mug.

Weston Neil Andersen
Founder of Andersen Studio- Andersen Design

My father, Weston Neil Andersen, fell on the pavement last April and suffered a serious brain injury, from which he is still recovering. He says in a considered tone that they tell him he is 89 years old but he isn't sure that he really believes this. Neither age nor brain injury is a cause for my father to retire, and so I like to tell him, that Eva Zeisel, his instructor and colleague is now 104 years old.

We always serve Weston's coffee in one of the mugs that he designed and Andersen Studio produces. Dad often holds the mug out at arms lengths and with a sly smile he says "Now that guy is a good designer!".

Recently a couple of our favorite mugs were broken and so I decided to cast some new ones, as I too missed having my morning coffee in my favorite mugs. I thought of the pleasure Dad would take in drinking his coffee in a brand new mug.

Three mugs in the fettled green ware state
copyright Weston Neil  Andersen 1989 

As I was casting and fettling the new mugs I recalled that shortly before father fell that he spoke of an idea of doing a brochure of just the mugs and using it to market the mugs as a line onto themselves. I thought about how post-injury, Dad is trying to find a way to engage in the business but his language skills do not always meet the ideas he has floating around his head. It was then I decided to follow through on the idea Weston had been engaged in before he took a spill that led him to Maine Medical and then to the rehab center.

Weston Neil Andersen designed a beautiful series of mugs, which has never been made available to the market beyond our retail shop in East Boothbay, Maine. The design of the mugs are not suited to the "cookie cutter " presses used to manufacture mugs in China and other low labor cost countries. These are designs specifically suited to the handcrafted ceramic slip-casting method.

The slip-casting process begins with testing the liquid slip for it's water content using a measuring flask and a gram scale.The ideal measurement is around 176 -180. The liquid slip has to be of a consistency to easily and smoothly flow into and out of the mold's forms. If the slip has the right amount of water but is still too thick to flow easily in and out of the mold, the viscosity must be adjusted by adding a small amount of Darvan.

Once assured that the slip's viscosity is right, it is a wise idea to pour a test cast for twenty or thirty minutes to see the thickness that is produced after the liquid slip is pour out of the object. We find that our cobble makes a perfect testing form as it is an open form that will readily release moisture. After the piece is poured and dumped, one waits until it has dried enough to maintain its form, then one takes a flexible fettling knife that can easily be bent to accommodate any shape, and runs the bent knife along the upper edge of the mold leaving as little excess along the lip as possible. If the thickness looks good then one proceeds to fill the molds.

    
 Tea Cup with curving lip in green ware state after being fettled.
Copyright 1989 by Weston Neil Andersen

With Mugs I like to have a thin lip but not too thin as then the finished mug will easily chip. Sometimes one can take the green ware and even out the edge of the lip on a slab of marble with water poured over it, but as I was working on one of Dad's designs, what we call the Tea Cup, I noticed that the form is not intended to have a flat rim but that there is a quite graceful and subtle oval dip in the lip on the side of the cup used for drinking. This form has not been cast very often and it appeared that this pleasing detail was sometimes missed by the fettler.

Ideally the exact detail can be achieved by the slicing process that is applied to remove the extra clay from the mold defining the form of the lip. Sometimes, this may need a little adjustment. I have found that a fresh rolled piece of sandpaper is ideal for gently recreating the curve of the rim.

It is easy to break pieces during the fettling process, particularly if they have taken in moisture while working on them. A good fettler must have an awareness of when the form has reached that point of moisture when just holding the form with a slight amount of pressure can cause it to break in one's hands. The fettler must then have the wisdom to set the form aside to allow the moisture to release before finishing the piece

The curves in Weston's mug designs are beautiful and provide great satisfaction for the fettler who removes all the excess clay and mold marks to highlight the beauty of the form.

5 mugs in the fettled green ware state.
copyrighted by Weston Neil Andersen circa 1989
 

Once one has developed a familiarity with the form and what is needed to highlight the quality of the form, the next challenge for a production fettler  is to develop methods of achieving the quality in the shortest amount of time. This also involves an awareness of how far to go with the detail in the green ware and when it becomes futile because some details will be taken care of in the glazing process. A ceramic production requires synchronized team work. Each stage of the process affects and is affected by a later or earlier stages in the process.

2 mugs in  fettled greenware state.
Copyright Weston Neil Andersen circa 1989

Next - Decorating and Glazing the mugs after Bisque Firing 

This is an ideal project fpr collaboration with a ceramic slip-casting operation. See Andersen Studio's Vison statement.

Photography by Susan Mackenzie Andersen

The History of Ceramics - Chapter One

Ancient Indian Coiled Pottery Pot 
from The Mid-Western United States
Photo courtesy of Barnhill Indian Trader

The beginnings of human history are cloaked in mystery, but as speculation goes, Ceramics emerged around 8000 BC during the Neolithic Revolution when man first started using tools and developing agricultural skills. This produced a need for vessels to carry and cook the produce.

There is one exception that calls for mentioning, Dolni Vestonice in the Czech Republic, where models of animals and a Venus figurine have been dated to about 25,000 years ago

The first vessels were baskets. The ubiquity of early coiled ceramic forms, from the Middle East to China to the America’s, suggests that pottery was first discovered when baskets were coated with clay so that they could hold small seeds and grain. Then one day the basket fell into the fire and it was discovered that heating hardens the clay making it more suitable as an airtight vessel. This event occurred synchronistically in different parts of the globe


Around 5000 BC it was discovered that by burnishing the half dry clay with a stone or a bone a smooth and more airtight surface could be created.


Ash firing was discovered when a pot was placed upside down on hot coals, reducing the surface of the rim to a glossy black. The upside down vase was also the first kiln. Then came the hole in the ground above which a bonfire was lit. Later the hole in the ground became a cave in a hill. The Chinese and Japanese expanded this into a complex system of successive chambers climbing over the slope of the hill

The kilns designed by the ancients are still in use today but have undergone modifications due to changes in fuel, materials, and the need for larger scale production. The greatest revolution in the technology of the kiln came with the discovery of electricity. The electric kiln simplified the process of firing as well as making it safer. This increased the popularity of the art of making the ceramics.

At first all pottery was made by women as part of the household chores, but as civilization developed, the “market” made its appearance and pottery became the work of the skilled craftsman. Around 3000 B.C, a simple revolving wheel existed in Mesopotamia, the area between the Tigris and the Euphrates Rivers The potter’s wheel economized the production of ceramics. By 4000 BC pottery making was predominantly masculine and the use of the potter’s wheel was commonplace.

The origins of mold making are traced back to Hellenistic Greece and the Roman Empire. This was a clay bowl with a design pressed into the inside. It was fired and then clay was hand pressed into the inside. A potter’s wheel was used to spin the surface until it was smooth. As it dried the clay reduced in size so that the “green” clay form was easily removed from the fired clay form.

Plaster, needed for molds used in ceramic slip casting dates 9000 years. The Romans cast in plaster to make copies of Greek sculptures and so it is much to my surprise to learn that the development of slip casting is credited to Ralph Daniel of Coolidge, Great Briton at the late date of 1743. I’ll be looking into this and reporting what I learn in future posts.

POST NOTE
During the process of researching this series I have been using both the Internet and my father’s old ceramics books, some of them dating to the days in the 1940’s when Dad studied ceramic slip casting in the Industrial Design department at Pratt Institute . His instructor was none other than the illustrious Eva Zeisel. Eva was quite taken aback when dad told her that he was actually going to move to Maine and start a hands-on ceramic slip casting studio of his own. This is what brings the organic quality to my parent’s designs, distinguishing their work from their more famous mid-century contemporaries who primarily designed for large production companies.
 
I love the process of a small slip-casting studio and I have also been enjoying researching and writing about the History of Ceramics. I look forward to continuing this discussion of The History of Ceramics and will continue it on this blog, Talking About Ceramics.  

I hope you enjoyed reading this at least half as much as I am enjoying writing it.   

The next email in this introductory series will be The Science of Ceramics. I can’t wait to dig into more of my father’s old books.

You can sign up to receive this email series and other news of interest on Andersen Studio's Home Page. 

One of my favorite references for this article has been Ceramics- A Potters Handbook by Glenn C Nelson, 1971 

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