The cause of lava lamp cloudiness is unknown, but this foggy affliction can leave lava lamp watchers feeling not so far out. According to lava lamp site Molten Meditation, you can restore your lamp to working order with some basic household materials and a little TLC.
Begin with a lava lamp cooled to the point that the wax inside has solidified. Fit the spanner around the cover at the base of the glass enclosure and unscrew the cover to remove.
Pour the liquid off the inside off the lamp down a drain, taking care not to disturb the wax. Gently rinse the inside of the lamp, directing the stream of water against the top edge of glass rather than directly on to the solidified wax. Pour off the water.
Repeat the rinsing until the water runs clear, showing no signs of bubbles or oily residue. Fill a final time with clean tap water and place the lamp back in its base, leaving the lid off. Turn the lamp on and allow the lava lamp to heat until the wax has fully melted.
Drip three droplets of washing-up liquid into the lamp.
Stir 50 grams of Epsom salts into a half-filled glass of water until completely dissolved. Continue to add Epsom salts to the glass 1 tsp at a time, stirring after each addition, until they no longer dissolve. Place the glass in a bowl of hot water and allow it to stand for five minutes, or until all salt crystals have dissolved.
Dip the straw to the bottom of the saltwater glass and place your finger over the end. Keeping your finger in place, transfer the straw to the uncovered end of the lava lamp and press it to the inside rim of the lamp neck. Release your finger from the end of the straw, allowing the saltwater to drain into the lamp.
Wait five minutes, observing the lamp. Drip in one straw of saltwater at a time, observing between additions. Watch for the formation of large wax globs that float all the way to the top and then sink slowly to the bottom of the lamp. Once this occurs, your lava lamp is cured of cloudiness and restored to normal working order.