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Ceramic Materials — What's That?

Not so short – Overview
I am often asked to describe the clay that we use and I am asked to clarify the difference between various clay types. All of this gets somewhat confusing for the average person because identical terms are often used to describe entirely different things. Marketing - is the all powerful reason that technical ceramic terms are not always used in accordance with their dictionary definitions.

Clay Types - Clays are naturally occurring alumina silicate compounds that have a curious capacity which is called plasticity - the ability to be easily molded or formed without cracking. The plate-like particles of clay are separated by lubricating water which together with surface tension creates the quality of plasticity or extensibility.

Clays may be kiln fired to vitrification - fused to a glassy matrix - where they become usefully hard and are essentially transformed into stone. Once fired there is no going back - short of the eons long natural weather process that eventually erodes everything. OK - so what kind of clays are found in the natural environment.

Earthenware Clay - Red clay flower pots and chimney bricks - are made virtually everywhere and get their distinctive color and lower firing range primarily from various forms of iron oxide which is a flux and colorant at kiln temperatures. With a high level of iron, earthenware begins to vitrify at approximately 1000 degree centigrade. Items made from this clay are relatively inexpensive due to the availability of the material and the lower firing temperature.

Generally speaking wares made from earthenware are not as a group as vitreous or durable as other higher temperature clay products. However - with proper body formulation earthenwares can be made both vitreous and strong and can be adjusted to fire over a range of temperatures. .

Fire Clay - This clay type - though somewhat less common - is frequently used to make brick for fireplace linings or as a component in refractory cement. Fireclay and related Stoneware clays are generally lower in iron content and as a result vitrify or mature at a higher temperature - beginning at approximately 1200 centigrade.

Kaolin - This clay type is the purest form of naturally occurring clay. The word Kaolin originally derived from the Chinese who have forgotten more than we will ever learn about clay and clay working.

One of the more common Kaolins is called Edgar Plastic Kaolin or EPK which is mined in Florida and used extensively in the pharmaceutical industry - Kaopectate, etc - as well as the applied clay products industry.

Virtually all of the major bath fixture manufacturers use clay bodies based on Kaolins together with another related clay called Ball Clay. Kaolin based bodies - like Porcelain - can be made to vitrify at different temperatures - with the range beginning around 1250 centigrade.

China Clays - Now this is where it gets interesting. You have no doubt heard of China or maybe even China Clay - as in fine China plates etc. China is a term coined by Europeans who were unable to copy the Porcelain produced in China because they did not have the naturally occurring plastic Kaolin - or China Clay - deposits the Chinese were fortunate to have.

Additionally - Europeans did not understand how the Chinese got their kilns so hot. In the spirit of friendly competition the Chinese thought it would be fun to see how long it took everyone else to figure this out. Actually they probably hoped that no one would. With a bit of persistence and a lot of idle tinkering - the western mind found they could mix something they had a lot of - bone ash (yes - from animal bones) to get something that sort of resembled Chinese Porcelain.

Eureka - they called it China or Bone China and began to convince people it was something really new and special that everyone should want and have. So you will begin to see - this is what happens to technical ceramic terms - they get hyperbolated by the marketers. Vitreous China - Bone China - Sanitary Ware - Iron Stone are all marketing terms that have gradually found themselves in common use and this has created a certain amount of confusing regarding the meaning of the terms.

What is Pottery?
Pottery is simply a common term used to describe a functional item made from clay. It is frequently used to refer to items that are not very durable - such as red clay flower pots that are never intended to be vitreous or durable. It can also be widely applied to items that are very high quality and equally durable.

I could be described as a Potter making Pottery Sinks or alternatively called a Ceramic Artisan or even Artist if your mind – unlike mine - finds that description attractive.

  Quality Assurance - Anyone who takes the time to carefully read and reflect on the information contained on this page will realize that I pay considerable attention to detail in general and specifically to the materials that are the basis for our product.

I have a Masters Degree in Ceramic Design and much more importantly forty years of practical experience which I use to ensure that you will be satisfied with my product. In fact I guarantee this result.

Clay Bodies - I develop all of our own clay bodies and I test and adjust them continuously to avoid problems stemming from poorly processed materials and materials with changing chemical anaylsis.

The ceramic industry as a whole has virtually no concern for the needs of small clay production shops like Water Stone & Maine Kiln Works and they make no attempt to provide materials specifically suited to our needs. We are forced – as a result – to do our own testing and comparison to stabilize and control the quality of our product.

To support this enormous effort I use computer based software to develop, test and record all of our body and glaze formulas. Specifically I use and recommend Glaze Master & Insight for these purposes.

I additionally use the professional services of Ron Roy - a widely acknowledged and highly skilled ceramic consultant. Ron's range of experience adds considerably to the quality of our product.

Stoneware - Water Stone makes extensive use of non-porous Fire Clay based vitreous Stoneware bodies for many of our bathroom sinks. This fired material is hard and durable - absorbs no moisture because the interface is literally a fused glassy matrix which believe it or not derives much of its strength from a begillion needle-like crystals (called Mullite) as long as your finger.

Stoneware iron content is relatively low but not so low that the iron impurities do not pleasantly color the fired clay. Stoneware bodies are frequently cork colored - light tan to medium brown depending on the percentage of iron present.

Additionally - most Stoneware has slight random iron speckling which typically flecks through the fired glaze giving it a distinctive character.

We mix and prepare a range of Stoneware bodies in our own Dungeon mixing room - using a large navy surplus mixer which produces individual batches of 200 plus pounds. Our mixing schedule results in 4 or 5 tons mixed in single day's session. Beck Strong - where are you?

We also make sinks from Porcelain which fires at 1260 degrees centigrade. It is very hard & durable and it rings like a bell. This more highly refined material is somewhat more costly - it does not have random speckling and unfortunately for us the drying and firing loss is quite a bit higher. Nevertheless - our glazes look spectacular over the Porcelain and we like it a lot.

Proper mixing of Porcelain is a critical and difficult process requiring equipment that is beyond our reach. All of our Porcelain is currently supplied by Tucker Pottery Supply - an outstanding Canadian company that - in my opinion - is the very best clay pre-mixer on this continent and most likely any other.

Frank Tucker is both a gentleman and a critical resource for Water Stone. He is consistently helpful in sharing his hard earned experience, I would not be making Porcelain sinks without Frank's help and support.

Ceramics - is a broad descriptive term that refers to any item that is made from fired naturally occurring mineral compounds. The term literally means - fired earth. In common use this term has been co-opted by the hobby slip ware industry as a distinctive reference to any ware that is slip cast and dependent on their industry supplied tools, glazes and related materials.

The marketing use of this term has been quite aggression and so the peculiar narrow reference for this term has fallen into common use or misuse depending on your perspective. Many people ask if I do Ceramics - in an attempt to classify my work into this hobby category.

Since I mix and prepare all of my materials and do no slip casting - in this sense I do not do "Ceramics". On the other hand - all of my work can be accurately described as Ceramics if one actually understand what this term means.

© Water Stone Sink 2014 -
115 South Gouldsboro Road - Gouldsboro, Maine 04607 - sales@waterstonesink.com - 207 963 5819
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