A Recipe Stand: Which Materials Fit?

Parts for a Kitchen Recipe Stand

A cooking club is comparing designs for a recipe-card stand. The stand will have an upright viewing panel in front of the card and a soft band that curves around the base to hold a cleaning cloth. Before choosing parts, the club tests samples from a supplier. The possible materials are aluminum, clear acrylic plastic, white acrylic plastic, blue silicone rubber, and cotton felt. Each coded sample is one of these five materials.

An adult supplies smooth strips with rounded edges. Each strip is 12 centimeters long, 4 centimeters wide, and 2 millimeters thick. The students change the material while keeping the strip dimensions and testing steps the same. They test the known materials first to make a reference record. They repeat each test with a second strip of the same material.

For the light test, students put each strip between the same lamp and a printed card. They record whether they can read the card through the strip. For the bend test, an adult gently tries to curve each strip around a cylinder that is 10 centimeters wide. The adult stops if the strip resists bending. Students record whether it curves easily. They do not force, crease, or break a strip.

For the electricity test, an adult sets up a classroom tester powered by a small battery. A lamp lights when the dry sample completes the path between two clips. Students use the same tester and clip spacing each time. They do not use wall outlets.

Finally, students measure each dry strip's mass. They soak it in room-temperature water for five minutes, blot its surface in the same way, and measure its mass again. Wet mass minus dry mass gives water gain. A result of zero means no gain was detected to the nearest gram. Both rounds of reference tests give the results below. The club then tests coded strips using these same procedures.