Giant Sieve Sorter

Boundaries are the gift that keeps on sifting.

Create a series of boundaries that keep some things out while letting other things through.

Note: There is now a readily available, competitively priced commercial alternative you may wish to explore before (or instead of) undertaking this Snack. It may be worthwhile to weigh the cost-benefit of building the Snack from scratch versus buying its commercial counterpart.

Subjects:

Keywords:

separations

Tools and Materials

Clear tennis-ball container
1/4-inch (6.35 millimeter) and 1/2-in (12.70 mm) mesh wire cloth, plus 1-inch (25.4mm) mesh chicken wire, cut into 4-inch squares (these three kinds of screens are standard sizes and should be available at most hardware stores)
Sharp knife
Scissors
Wire cutters (may not be necessary)
Duct tape (2-in width)
Several objects of four different sizes ranging from 1/8 to 2 inches (3 mm to 50 mm)—e.g., peppercorns, garbanzo beans, filberts, and walnuts

Assembly

Cut the tennis-ball container into four roughly equal sections with a knife.
Take the bottom section of the tennis-ball container and wrap duct tape all the way around the rim, extending 1 in (2.5 cm) above the rim. Cut slits in the tape from the top down to the rim of the container at intervals of 1 in (2.5 cm). Peel back the tape as if you were peeling a banana.
Trim the smallest screen—the 1/4-inch (6.35-mm) mesh—into a 4 x 4 in (10 x 10 cm) square by either cutting it with the wire cutters or by bending a four-inch section back and forth until it breaks off.
Center the screen over the bottom section of the container and roll the peeled-back sections of tape onto the screen to secure it.
Wrap tape around the top and bottom of one of the middle sections of the container, with the tape extending about 1 in (2.5 cm) beyond the top and bottom. Cut slits into the tape around the bottom of the section at inervals of 1 in (2.5 cm) and peel it back.
Place this section of the container on top of the bottom section and tape it to the screen.
Following the same procedure, attach the next two sections of the can, placing the 1/2-in (12.7-mm) mesh between the second and third sections and the 1-in (25.4-mm) chicken wire between the third and fourth sections.
Wrap duct tape around the edge of each screen so there are no sharp edges.
Fill your container with a mixture of all four sizes of round objects. Use only a few of the largest objects and progressively more of each smaller size. Put the cap on the container.

To Do and Notice

Hold the container upright and shake it. The round objects will fall through the screens until they hit a screen that they are too big to fall through. You should end up with the objects all sorted out on each of the four levels!

Turn the container upside down and shake it, and all of the objects will end up in the top section of the container.

You can uncap the container, remove the objects, and add different ones. Try to find other sets of objects that are the right sizes to be sorted by the giant sieve.

What’s Going On?

This is a sieve that sorts objects by size. Its screens act as boundaries, allowing objects that are small enough to pass through and preventing the passage of objects that are too large.

There are many natural boundaries that sort objects by size. A familiar example is a small animal hiding in a hole small enough to act as a boundary to its larger predator. No boundaries are perfect; all allow some things to leak through. Boundaries that determine passage based on size are common.