CHOICE OF CLAY

When I decided to embark on this adventure the first thing I had to decide was which clay to buy, I thought that there was only one clay, and that it was of different colours, but no, the world of clays is very complex, there are many types of clay and depending on what you want to do you can choose one or another.

I read the catalogues of every pottery shop I could find on the internet and I learned about the different types of clay and their uses. To sculpt we need a plastic clay, that means we need a clay that can be modelled in it and keep the shape you want to make, the less plastic, the more difficult to sculpt, for that reason many ceramic clays contain chamotte (ultrafine grains) so that the clay adapts to the shapes and is easier to model with it.

Therefore, one of the most important decisions we will have to make when we start modelling is the choice of clay, there are many types of clay on the market, and so much variety can confuse us, so it is important to know what we want to do and what kind of material to choose to give life to our ideas.

First I will talk about the different types of clay that we can currently find in the market and then I will talk about the water based clays that are the clays that I use for my sculptures, since I make ceramic sculptures, that means that after modelling them I need to take them to a kiln to get the final piece.

Let's start with the technical class,

OIL-BASED CLAY OR PLASTICINE CLAY

These are pastes containing various combinations of oils, waxes and clay minerals. Oil-based clays remain malleable even when left for long periods in dry environments. Articles made from oil-based clays cannot be fired and are therefore not ceramic. Because the viscosity of oils decreases with increasing temperature, malleability is affected by heating or cooling the clay. Oil-based clays can be heated, melted and then poured. Oil-based clay is not soluble in water. It is available in a multitude of colours and is non-toxic.

With this type of clay, it is usually sold in different hardnesses, soft, medium or hard, depending on the texture you like to work with. The ideal is to make a mould after finishing the piece in order to preserve the work.

Among the best known brands are Chavant, NSP and Monsterclay.

POLYMERIC CLAYS

This is a type of modelling clay based on the polymer polyvinyl chloride (PVC) that can be hardened. Polymer clay is generally used to make art and craft items, and is also used in commercial applications to make decorative pieces. Art made with polymer clay can now be found in major museums. Polymer clay remains workable until it cures, usually between 129 C and 135 C for 15 minutes for 1 ⁄ 4 inch (6.4 mm) thick. This temperature is significantly lower than that of mineral clays and can be achieved using a home kiln. The clay does not shrink when cured.

Brands of polymer clay include Fimo, Sculpey, Premo, Cernit, Formello, Modello, Du-Kit and Kato Polyclay.

EPOXIES.

Epoxy is a self-hardening clay. It consists of two components, which must be mixed in equal parts, homogeneously to harden, the time varies according to the amount that we prepare, it is better to work with small quantities to control the process. It can be slightly wet with your fingers to smooth the surface. It does not need firing in the oven. Once dry, it can be sanded, drilled and painted.

ARCILLAS CERAMICAS

Ceramic clays are classified into five classes; earthenware clays, stoneware clays, ball clays, fire clays and porcelain clays. The three most commonly used ceramic clays are earthenware clays, medium-fired stoneware clays and high-fired stoneware clays. All three are commercially available in wet and ready-to-use form. Clay bodies can also be produced by mixing dry clays and additives with water to create your own desired clay body.

EARTHENWARE

Were some of the first clays used by potters, and are the most common type of clay. The clays are easily worked and can be sticky. Earthenware clays contain iron and other mineral impurities that cause the clay to reach an optimum hardness between 950 °C and 1100 °C.

STONEWARE

Are plastic and often grey when wet. Their fiery colours range from light grey and beige to medium grey and brown. The fired colours are greatly affected by the type of firing.

BALL CLAY

They cannot be used on their own because of their excessive shrinkage during drying and firing. However, they are extremely useful when added to other clays to increase their plasticity.

REFRACTORY CLAYS

The hallmark is their high firing range. They mature at approximately 1500°C. Although relatively free of mineral impurities, they tend to have iron flecks that give them a mottled appearance once fired.

KAOLIN

Because of their mineral purity, kaolin clays are used for porcelain. Although kaolin clays have a certain range of colours, they are all very light in colour. While wet, they will be light grey and will fire in the range between a very light grey or beige, to almost white and white.

PAPERCLAY

Are sometimes referred to as fibroclay - any clayey mass to which processed cellulose fibre has been added (paper being the most common). Earthenware, terracotta, stoneware and porcelain clay bodies can be converted into paper clay. The fibre increases the tensile strength of the dry clay and allows for dry-to-dry and wet-to-dry bonding.

To get an idea of the qualities and qualities obtained by the different pastes, after firing, we will say that:

1. When they have a red or yellowish colour and their texture is porous, it is called terracotta or pottery.

2. When the colour tends to white and its texture is porous, it is called earthenware.

3. When its colour is between yellowish and grey, and some elements of its composition have been vitrified, and its texture is not very porous, it is called stoneware.

4. When it has a semi-transparent white colour, with an impermeable texture, it is called porcelain .

Knowing all this, it is time to choose the clay that best suits what we want to do and our sculpting preferences.

I chose porcelain, which i love for its whiteness, it works very well with the sculptures I make, preferring the flax paper clay porcelain, because it allows me to model in detail, make complex constructions and maintain the whiteness of the porcelain. It is a complicated clay, as it is very sticky and soft, it took me a while to get the hang of it, but now I wouldn't change it for any other. I also work with stoneware, which is easier to use and also gives me good results, but it doesn't have the whiteness I'm looking for.

As you can see, choosing our type of clay is a personal process and taste, and the only way to find out is to try it out.

So let's get down to work.