The Sensorial Materials consist of a wide range of materials that the children work with independently. Each material is designed to isolate a specific tangible quality of a thing, such as its height, length, color or smell.
Differentiating dimensions and ordering by size. This group of exercises includes the materials known as the Pink Tower, Brown Stair, Red Rods, and the Knobbed and Knobless Cylinders.
The knobbed cylinders, is a set of four oblong blocks of natural colored wood. Each block contains ten cylinder-shaped insets (with knobs on top) that can be removed and reinserted by the child. The cylinders vary in height and width. In one block, only the width changes; in another, the height; in the third, both increase together; and in the forth, the height decreases as the width increases. A child works with these materials by removing the cylinders, mixing them up, and replacing them in the proper holes. If he makes a mistake, for example, by placing a thinner cylinder in a hole that is too big for it, he will discover his error on his own. In the words of Dr. Montessori: “In the end, there will be a cylinder left over that cannot be fitted into the still empty hole. . . . His attention is brought sharply to bear upon an obvious problem. He must take out all the wrongly place cylinders and put each of them back into its proper place.”
Training all senses to discriminate fine differences. These materials include the Smelling Jars, the Baric Tablets, the Musical Bells, the Sound Boxes, the Object Bag, the Swatches and the Color Tablets.
The Color Tablets, for example, are a set of small wooden rectangles covered in different shades of colors, contained in two boxes each containing sixty four colors, that is, eight different tints, each of which has eight shades graded from lightest to darkest. Initially, the teacher offers a few bright shades for the child to pair. Next, the child progresses to pairing a dozen shades, then to sorting all sixty-four in neatly arranged rows of gradation—and later, to picking out one particular shade and finding something in his environment that corresponds exactly to it. As his skill in identifying and grouping colors improves, so his attentiveness to his environment increases, and the joy he receives from the exercise multiplies. Dr. Montessori observes: “The children are very fond of this exercise in ‘color memory’; it makes a lively digression for them, as they run with the image of a color in their minds and look for its corresponding reality in their surroundings. It is a real triumph for them to identify the idea with the corresponding reality and to hold in their hands the proof of the mental power they have acquired.”
Understanding basic geometrical shapes and solids. The geometry materials in our primary classrooms include a set of wooden geometric solids (such as spheres, cylinders and prisms); the geometric cabinet (which includes flat wooden insets representing different types and sizes of geometric shapes, such as triangles, rectangles and circles), and constructive triangles (flat triangles of different sizes with which the child can construct all manner of straight-lined geometrical shapes.) Our students handle these shapes, learn their names (such as “rectangular prism”) as part of their vocabulary work, and thus build a concrete foundation for the later study of geometry: it is much easier for a child to understand what a prism is when she can hold it in her hand.