Clay

Introduction

Clay comes from the earth and is made from a group of miniscule minerals held together by water. This makes Clay a very versatile modeling material. It is shaped using water to keep it maluble until the final object is created. There are two basic types of clay: Kiln fired clay and air drying clay. Kiln fired clays include terracotta, stoneware, earthstone and porcelain. You can add paperclays to kiln fired clays to improve their strength whilst still remaining lightweight. Clay objects that have been fired are then glazed with pigmented solutions to produce a multitude of aesthetic finishes.

Air drying clays are ideal for maquettes or small sculptures. Newclay, Claydinium, Chavant and Milliput are the most popular air drying clays. Another type of clay called Super Sculpey is fired in a household oven. Air drying and oven baked clays can be sanded and painted once dry.

Techniques

There are three main techniques using Clay; Pottery, Ceramics and Model Making. Pottery is the art of spinning wet clay on a potters wheel to create a three dimensional hollow form. Examples of this are vases, bowls and sculptural vessels. The great advantage of using a Potters Wheel is the amount of objects you can spin, lending itself well to mass production.

Ceramics are products such as plates, mugs and cups, which have been fired using a kiln and then glazed. Sometimes Ceramics are dipped in vats of glaze to stain them and sometimes they are hand painted. If you already have a plain dinner set of plates and bowls, why not decorate them yourself using ceramic paints? Pebeo do a fantastic range of paints for this called Vitrea 160. All you need is a domestic oven to cure the paint onto the ceramic and then you're done. You can buy Ceramic Paints here from Everglades Craft Materials Supplies. Try it today!

Another technique using clay is Model making. You can model air drying clay over an armature to keep it strong. Armatures can be made of metal bars tied together with wire, wire mesh or even cardboard. Remember that the clay will shrink slightly as it dries, so make sure your armature is well buried underneath your clay. If you need to work on your project longer than your time allows for one day, remember to cover it well will plastic bags to keep the moisture in. The next day, if you need more moisture, just apply water. There are a multitude of modeling tools available for working with clay. I recommend using the wooden ones as they are especially smooth. Remember you will need to work in the round, so always use a suitable modeling stand for your work. They really are a valuable piece of equipment.

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Plaster

Introduction

Plaster or plaster of paris technically speaking, is calcium sulfate (in its powdered state) or gypsum (when water is added). Plaster is a fantastic casting material and works well with models made from clay. Casting is all about reproducing your model either once (a lost cast) or more often, many times.

Plaster can also be used for model making, using a bandsaw, carving tools and sanding tools. It can be reinforced with plasterers scrim or layered up around and armature (as with clay) using plaster bandage or chopped strand mat. If you are modeling with plaster in this way, remember to always mix up the smallest amount of plaster needed as it will always dry sooner than you expect.

Techniques

First of all you make a supporting structure for your model to be placed in and your plaster to be poured into.The simplest of structures for making a mould is using five pieces of wood, some scraps of clay to seal the edges and some string to secure it all. This will make your mould - it will have half of the negative shape of the object you are casting within it. Whatever material you pour into the moulds to make you final cast will be joined together in some way specific to that material. If you need your final piece to be completely whole, ie, without a join, you can make a one piece mould by using the two halves of the plaster moulds and joining them together with string. You will need to make an indent in each of the moulds to use to pour your casting material into.

The great thing about plaster is that with varying amounts of water you can produce very detailed or less detailed casts. Remember always to add your plaster to your water, not the water to the plaster. And always cover your model with a release agent (such as petroleum jelly)so it comes away from the plaster easily and so that you can re-use your model afterwards. You can cast a plaster model in a plaster mould using plasterers soft soap as a release agent.

 

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