What household items can I use to demonstrate clean vs dirt instantly?

Question

items as milk, food coloring, vinegar etc.

Answer 1

Once for a Sunday school lesson I used cocoa powder on a box to make it look really dirty while actually not having to be exposed to actual filth! So I guess you could take two items, plates for example, and rub some cocoa powder on one.

Answer 2

If you have a vaccum cleaner that has a removable cylinder to catch nasties, you could empty some of that into a plastic baggie, and really be able to show off dirty without having to touch it. Or some old nasty stained clothing that's "clean" but doesn't look clean can be used for such a demo as well. :-)

Good luck!