Keeping the shells

Original non-fiction-style practice text.

The potter, Emi, kept the shells which visitors pressed into her clay tiles. They were not valuable, and she did not sell them. Each shell stood beside a finished tile bearing its impression. The shallow ridges on one tile had come from a deeply grooved shell; the clay had failed to reach the narrowest spaces.

New learners could compare the object with the mark it produced instead of assuming that every detail would transfer. They could also try different pressures on a spare piece of clay. Emi cleaned the shells gently after each session and returned them to the same tray. When a teacher asked to borrow only the finished tiles for an exhibition, Emi offered the shells too. The point of the display was the relationship between them. Without the objects, it would show attractive patterns while hiding the practical question she wanted learners to investigate.

Give two ways in which keeping the shells helps new learners.