STONEWARE

WHAT IS STONEWARE CERAMICS

With this term, or directly stoneware, are known those pieces fired at a relatively high temperature, 1800º F-2400º F, and made of a non-refractory clay that usually contains iron, carbon and a series of other materials that give it a non-homogeneous appearance and color. The composition of stoneware may include ball clay, quartz, chamotte or feldspar, which is a flux.

Sometimes there is confusion between what is ceramic or stoneware, you just have to know that this is a type of ceramic.

CHARACTERISTICS OF STONEWARE CERAMICS

Historically it is considered a ceramic that began to develop after earthenware and predates porcelain, at least in Europe.

Structure: It has very little porosity, so it is suitable to contain liquids, generally it can be in contact with them constantly, although its impermeability will also depend on whether it is vitrified or not.

It is quite resistant to acids.

Compact and resistant material.

Color: It usually has a gray or brownish color due to the composition of the clay.

Hardness: According to the Mohs scale it would be between 3 and 8 as maximum.

This scale goes from 1 (Talc that can be scratched with a fingernail) to Diamond (the only mineral that can only be scratched by itself).

Difference between stoneware and porcelain:

Darker and more opaque than porcelain and without its degree of vitrification.

When choosing porcelain or stoneware, these points should be taken into account:

Porcelain fires at and withstands higher temperatures, has greater hardness (it is more difficult to scratch) and is more difficult to chip when subjected to small knocks. It is, in short, more resistant.

Stoneware or porcelain, which one to choose?

Well, a porcelain piece will have a quality of being more translucent, especially at the edges and if it is thin enough, so it is considered to have a more “delicate” aesthetic. Stoneware will have another type of beauty, more “rustic”. Porcelain may be less resistant to very sudden changes in temperature, however, there is no problem in finding tableware that is microwave and dishwasher safe.

Handmade rustic stoneware tableware by Kari Ceramics

Difference between stoneware and earthenware:

Stoneware was conceived later than earthenware, in a way, it can be placed as a category between earthenware and porcelain. This type of ceramic, unlike earthenware, is heavier and generally not as smooth.

The firing temperature of stoneware is higher than that of earthenware, the latter having more porosity, being less impermeable and resistant.

Difference between stoneware and porcelain stoneware

Porcelain tile and porcelain stoneware are generally used interchangeably, these terms refer to a type of stoneware whose mass is harder and more compact, usually obtained by pressing. This gives it greater resistance to abrasion and greater strength.

On the other hand, some people also differentiate between porcelain stoneware and porcelain tile according to their water absorption level (from 6% to 0.5% for the former and less than 0.5% for the latter).

Porcelain tile has much less or no porosity, which makes it waterproof, that is, when in contact with water, it does not absorb any water. This is not always the case with common stoneware, which often requires a waterproofing layer.

Porcelain stoneware has a good capacity to resist sudden changes in temperature and is very resistant to weathering, rain, frost, etc., which makes it a very suitable material for outdoor use. Because of this and because it is also very slip resistant, it is widely used in paving.

It is very easy to clean and maintain and resists acidic materials, so it is often used on kitchen floors, as these areas are very punished by drops of vinegar, juices, etc., with the added benefit that it is difficult for stains to remain on them. They are also recommended in areas with high humidity such as bathrooms. Being very resistant, as we said before, it is also placed in high traffic areas.

These differences between stoneware and porcelain tile, which has had more treatments, mean that the latter has many more advantages, however, its manufacturing costs and greater difficulty of installation make it a more expensive material.

ORIGIN

The oldest pieces come from Asia, although there was not a great tradition in the manufacture of stoneware-type ceramic pieces called as such, practically most of the pieces that were made with this material were considered more or less pure porcelain. However, objects have been produced for more than 3000 years. The well-known Raku pottery frequently uses stoneware in its work.

In Europe, production started much later. The first pieces that could be considered stoneware ceramics are attributed to the Roman civilization, but this type of pottery was not very common at that time. Therefore, production was later than in Asia, due to the type of kilns they had in the old continent, which could not reach very high temperatures. Only until the twelfth century in Germany, it can be considered a fairly widespread production of this style of pottery.

TYPES OF STONEWARE

When fired with natural clays and unglazed, it is called natural stoneware.

Currently there is what is called pressed stoneware, which, as its name suggests, is compressed, subjected to high pressure. It is widely used in coatings for kitchens and bathrooms.

Extruded stoneware

Extruded stoneware is also composed of natural clay. Due to its high temperature firing and long life (up to 35 hours), it is of high quality, high hardness and great resistance. It has a water absorption of less than 1%. It is ideal for outdoor paving, where a very resistant floor is required, and it can also achieve a beautiful rustic effect.

Porcelain tile

The materials that make up porcelain stoneware are not very different from those used in porcelain, a clay with a suitable feldspar content that is fired at high temperatures. Perhaps the most notable difference with this porcelain (although they may be fired at similar temperatures and have similar compositions) is the higher proportion of kaolin in the case of the latter.

Porcelain stoneware is a completely impermeable material, very resistant to temperature changes and abrasion, and therefore differs from common stoneware, as mentioned above.

USES

Due to its hardness, it is widely used in flooring, with a wide range of tiles in different styles: rustic, porcelain, stone type, etc. An imitation wood stoneware tile is also marketed, which provides a cozy Nordic style. Also in tile coverings of other materials.

Vitrified stoneware can be found in sanitary ware, with a glazed cover.

Stoneware is one of the most used materials in pottery, it is used for vases, pots, bowls and countless kitchen utensils. In handmade ceramics this material enjoys great popularity and generates works of very beautiful textures.

Stoneware dishes:

Although unlike porcelain it is more likely to chip with a blow, it is very popular in bowls, plates, cups and other objects. Fortunately, traditional ceramic tableware is being recovered and unique handmade pieces are being used to put on the table, instead of industrial sets. Both at home and in the hotel and catering industry, we are looking for a return to handmade utensils that are original and unrepeatable.

WORKING WITH STONEWARE

Artist Lucinda Carod talks about this material and her relationship with it in the creative process:

“It starts with the cone, which is a way of kneading and centering the clay, a fundamental maneuver to be able to build/lift a piece.
In fact, potters say of their work stretching the clay upwards, starting from a base that is thick.
Stoneware is a friendly clay, it gives you a lot of leeway, it is quite plastic, it is quite moldable, but without running the risk of the piece collapsing by playing too much with its structure…porcelain does not admit mistakes, you have to be very clear about things before starting to work it: two or three movements and that’s it.

It does not contain so much kaolin, so it is possible to modify the shape, make it bigger, smaller… It behaves like an animal that I have to tame, to convince it nicely. In the end, it is a consensual submission, because if you use only force, you are not going to do anything…that is why you have to listen to the clay to see what it tells you…and you do it through touch.

I think it is a good working partner, terracotta also, low clay, what happens is that it is very thick.
This type of clay allows me to do more subtle works, sometimes I wait for it to have a perfect texture, a point like butter. I like to touch different clay and lately I am enjoying a lot the chamotte stoneware that helps a lot to hold the piece while I sculpt it… but its touch is rough and after that manipulation, I am left with war wounds in my hands, in the form of rubbing.
It is resistant, this is a feature that I like very much.

If it can withstand a second firing at 2400º F, after biscuit firing, it will be a material that will last a long time. In addition, it allows quite delicate work to be done, approaching porcelain.
In short, I would say that it is a material that is not only kind, but also quite noble in its behavior and in the way it relates to the hands that work with it; it follows you and gives you a lot of leeway”.

(*) Lucinda Carod lives in the Spanish province of Girona and teaches how to start working with clay in her “tallers presencials de ceràmica”.

Here are some frequently asked questions as a summary:

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