A Note on Materials
The Reflection Stands: There are many ways to prepare the reflection stands. The main idea here is to get a light reading from different surfaces by aiming a light sensor at each surface and observing the value it displays on the RCX when you use the View function. In order to compare the amount of light reflected from these surfaces, it is important to keep their distance from the light sensor constant. The stands should be constructed so that the materials used can be placed vertically on a table.
Surface considerations: We recommend using an array of achromatic surfaces (paper), including white, black, gray and highly reflective metallic silver, such as Mylar. A word of caution is in place here regarding the gray sheets. When we bought materials for our stands, we took an RCX with a light sensor to the art supply store and checked many gray sheets. We were surprised by how much light was reflected or absorbed by some. Some sheets looked lighter than others, but ended up reflecting less light because of their texture. Your objective is to find a gray that reflects a value in between the black and the white values.
Stand construction: We suggest cutting the sheets to size and taping one sheet onto each side of a small box such as an audio cassette case, so that each group will have 2 stands with 4 surfaces altogether.
Another way to prepare the stands could be to mount the different surfaces side-by-side onto a box such as a shoebox. To do so, first cut each sheet into rectangles about the size of a small index card then tape them to the side(s) of the box.