Almost no child of the '70s was without a lava lamp. These colourful, slow-moving lamps contain globs of a dense, waxy substance that floats through liquid in the lamp when heated. In recent years, lava lamps have been coming back into style with the younger crowd. These speciality lamps can be expensive. For a cheaper alternative, you can make one yourself. With a little bit of chemistry, you'll have a working lava lamp in no time.
Scoop about 3 tablespoons of petroleum jelly into a microwaveable container. Heat the jelly for about 30 seconds at a time until it is liquid; six to 10 times should do the job. Add about 6 tablespoons of mineral oil to the petroleum jelly and stir them vigorously until they combine. Pour the mixture into a sealable plastic bag. The mixture should become more dense as it cools but still have a slightly liquid consistency.
Nip a 4- to 6-inch piece of stainless steel wire and press one end against the centre of the bottom of the jar. Coil the wire into a loose, flat spring exactly the size of the bottom of the jar. Dip the spring in the liquid oil-and-jelly mixture. Set it on a paper towel and let it solidify.
Fill the jar about ¾ full of rubbing alcohol. Squeeze in the sides of the spring and drop it into the jar. It should float to the bottom; if it sticks, push it down with a wooden stick. The spring prevents the "lava" from sitting on the bottom of the bottle.
Cut a hole in one corner of the plastic bag. Squeeze globs of the mix into the rubbing alcohol, being careful not to splash. Top off the jar with alcohol if necessary, leaving about ½ an inch empty at the top. Cap the jar tightly.
Set the bottle on a battery-powered LED crystal stand. These stands get warm as all lights do, but will also shine colours into your lava lamp. Some even rotate slowly. Turn the power on to the stand. Once the lamp heats, the blobs of lava should begin their slow rise and fall in the jar.