Step 1: Get a basketball!
To fill the basketball, you have a few choices:
1.) I cut two slits in the ball, making a triangular flap.
I then taped the flap back, and filled my ball with sand.
Closing a flap is a little messy, but I had intended on taping the ball anyway, so it made my filling quicker.
2.) You could use an awl or a drill to put a hole in one of the black stripes on the ball.
Fill the ball with a small funnel, and then patch with a radial tire patch kit.
Step 2: Fill the ball
-If you fill using the small hole/funnel method, I think the only thing that you can do to pack down the contents is occasionally shake the ball to make sure that everything settles.
To fill the ball, I used an empty drink pitcher to pour sand through the opening cut in the ball.
Using a bag of play sand purchased from Home Depot ($4), the ball ended up at just below 25 lbs.
Dry sand has a density of around 1600 kilogram/cubic meter
Wet packed sand around 2000 kg/cu.m.
Some lighter household materials that would work for this instructable are:
Coarse salt is around 800 kg/cu.m.
Fine salt is around 1200 kg/cu.m.
Granulated sugar is around 850 cu.m.
Or improvise for your contents!
Just remember, sand makes a pretty heavy medicine ball by itself!