Liquid motion timers entertain with tiny coloured "bubbles" that slide from one level to another on plastic shelves suspended in liquid. Timers like these often grace desks in office cubicles, home offices and college dorm rooms. Shops sell them alongside magnetic toys and novelty posters. However, if you can't find a timer that suits your fancy, you can try making one at home. They're not just interactive decorations, they're also educational science experiments for all ages.
Snip the narrow tube at the bottom of the funnel to about half its length, giving the coloured bubbles a shorter distance to travel. Disposable plastic funnels, or cheaper versions, are usually very thin and easy to cut and manipulate.
Punch holes around the wide mouth of the funnel, spacing them about 1/8-inch from the edge. This gives the bubbles a way to pass back through the funnel.
Slip the funnel into the jar, holding it so the edges of the funnel's mouth sit against the inside walls of the jar. Hot glue the funnel into place and let the glue dry for 10 minutes.
Fill the jar to about 1/4-inch below the rim with water. The water should flow through the holes in the funnel easily.
Pour about a tablespoon of clear oil into a bowl. Add up to 20 drops of food colouring to the oil. It may take some vigorous stirring, but the colouring should mix with the oil.
Pull some of the oil into an eye dropper and squeeze it, one drop at a time, into the jar. These coloured "bubbles" should fall into and through the funnel.
Screw the lid onto the jar very tightly when you've added all the oil. To use the timer, flip it upside-down and time how long it takes the bubbles to fall through the funnel.