The use of three-dimensional materials, including clay, creates so many problems of organization in school that, except for Plasticine, they are probably not used sufficiently. They divide roughly into three categories—soft modelling materials, such as clay, Plasticine, dough and papier mache; carving materials; and hard modelling materials, such as card, scrap materials, paper and so on. Each of these has something to offer in the art training of children. All of them require a different kind of imagination and a different use of the hands from work in the flat. We have already seen that work in clay must be planned and looked at from all angles. This is true of all three-dimensional work. It requires a relating of shapes in space, a task we meet in adult life when we furnish a room.

Let us first consider the materials available for this work. We have already considered clay, which is, I think, much the most satisfactory of the soft modelling materials. What others are there? Plasticine has for many years been a favourite. To anyone used to working with clay it seems an unsatisfactory sort of material to handle. The two principal complaints against it are firstly that it is too expensive to give children the opportunity of working on a large scale, and secondly that it picks up so much dirt. It has, nevertheless, a valuable place. In particular it is often used to give small children the opportunity to work in three dimensions, in schools where the teachers are not prepared to organize work with clay. It is also an asset in making models from cardboard and scrap materials.

Flour-and-salt dough is well known in most Infant schools and is particularly useful for making things like "cakes" for a classroom shop or play house. One part of salt to two parts of flour usually gives a satisfactory mixture, and the addition of powder colour in the mixing produces many lovely and brilliant colours, which children find very attractive. These colours come off on the hands and clothes, however, so overalls are needed. This is not altogether an easy modelling material. It does not permit detail, and in general will not stand up. It is a material best used for relief modelling. It is also rather expensive.

Papier mache has the advantage of being a really cheap material, although it is troublesome to prepare and not very attractive to children in appearance, until it is finished by painting. There are a number of ways of preparing it. Perhaps the best, although not the least troublesome, is the following:

Tear up a number of sheets of newspaper into small pieces. Leave these to soak for two or three days and then boil them for about half an hour, stirring them and beating them from time to time. Strain the boiled newspaper through a piece of cloth and squeeze out all the water you can. Put the paper in a bowl and beat it with a wooden spoon. Add about two cups of jellied size for each four sheets of newspaper. Jellied size is prepared by adding boiling water to size and allowing it to cool. Mix the size and newspaper well. Now add some powdered whiting, and beat the mixture well. This should finally result in a clay-like substance, which is ready for modelling. As with dough, it cannot be used for detailed work, and it will not stand by itself. It takes a long time to dry out. Another kind of papier mache can be produced by putting layer after layer of paper on a prepared mould, with a layer of size or paste between each. This method is more fully described in the chapter on puppetry.

There are also a number of prepared modelling materials made by various manufacturers. Most of these are useful additions to the range of modelling materials. In general, however, they are too expensive for any considerable use.

Three-dimensional work in school ought to include some carving, but apart from the soft chalk which can be found in some areas, a suitable material does not really exist, so far as I know. Carving material for children ought to be soft, but sufficiently fine to allow for some detail. The ideal material in every particular, except the important one of price, is soap. Carving is a wasteful process in any case, and in my experience children need two or three blocks of soap before any interesting work is produced, so for general purposes this material must be out.

Block salt is another pleasant carving material, which is also too expensive to be of much use. Unlike soap, it does not allow of much detail, but the material itself has a quality which adds considerably to the finished work.

Plaster of Paris is a much cheaper material which can easily be made into blocks for carving. Buy plaster from a pottery supplier if you can, as it will be much cheaper. I find that plasters differ a little in the amount of water needed with them and it is wise to do a little preliminary experiment to discover exactly what proportions of plaster and water will produce a plaster which is satisfactory for carving, being neither too hard nor too soft. Measure the water into a bowl or bucket first, then add the plaster a little at a time. When it has all been added, stir the mixture gently with your hand, until it starts to thicken. Pour it fairly soon after this, because plaster thickens quickly. Blocks for carving can be made in old cardboard boxes, or cartons specially made by fixing pieces of card together with gumstrip. It is a good idea to make some irregularly shaped blocks, perhaps pouring plaster into a prepared hollow in some clay, or making a mould by using a wall of corrugated card, sealed on to a piece of board with clay. These irregular blocks often suggest new ideas. Keep plaster well away from any work which is to be fired, however, as it is a very messy medium, particularly when used for carving. Organization of such work needs careful planning, because plaster trodden into the floor is often difficult to sweep up. I try to do this sort of work in the summer, when there is a chance that we may be able to work outside.