Mass and weight

Another use for the film containers: Weighing things in space. They can't use a balance, so time vibrations. You tape the film container to a hacksaw blade, clamping the other end so the blade is horizontal. Some tissue in the bottom stops your weights rattling around and spoinling the calibration. Use 3, then 4, 5, up to 10 pennies to calibrate. You may need to do some trial and error here depending on your hacksaw blades, and remember to put some tough tape over the sharp edge. Once you've got your calibration curve you can weigh (sorry, find the mass of) small objects.