Another method would be to put a large saucer of clean water in the coffee can instead of the cardboard. Actually, you won’t need the saucer if the nail hole in the bottom of the can doesn’t leak. Keep adding water from time to time to make up for evaporation losses. After a few weeks, let all the water evaporate. Then check for the dirt.

     For part two of the experiment, remove the coffee can from the stand. Then wrap several strips of tape tightly around the can, sticky side out. If this is too hard to do, then try to get some double-sided tape. Or, just tie the remaining piece of white cardboard around the can, and apply jelly as before. Nail the can on the pole with the open end facing downward.

     Mark an arrow on the lid pointing to the north. Try to locate the stand as high as possible (on the flat roof of a building would be ideal). Check the can every few days to see if there are more particles coming from one direction than another.