• A bottle of whisky – It must have a screw top.
• Petroleum based wax – You can buy wax in bags from craft shops, but the best thing to do is buy a packet of cheap, white candles.
• Perchloroethylene (Tetrachloroethylene) – Perchloroethylene is usually called “Perc” and is widely used by dry-cleaners as dry-cleaning fluid. It is also a commonly used engine-degreaser. Have a look in the Yellow Pages for dry-cleaner suppliers or, easier, go to your local dry cleaner and ask them for a cup full. Treat it like you would treat turpentine or thinners, i.e. don’t drink it and use in a well ventilated room.
• A glass container for mixing
• A tin for melting wax in
• Something to make the base for the lamp – A piece of PVC pipe about the thickness of the whisky bottle will work. I used an old plastic water bottle.
• A cord with a switch, stand, and light fitting – You can get this at a craft shop or hardware shop.
  
• A 40 Watt light bulb
  
• Thin steel wire
  
• Wax dye – A craft shop is a good place to look.
  
• Table Salt
  
• Dish-washing liquid
  
• Acrylic paint
  
• Water
  
• Permanent marker

Wax is less dense than water when melted, so if you only use wax in your lamp, it will float up and stay there. By adding perc to the wax, it becomes denser. The idea is to get a perc-wax mixture that has almost the same density as water.

The right ratio of wax to perc is about 2:1. So, if you’re making 250ml of lava you need about 166ml wax and 83ml perc. You are going to pour the perc into the molten wax to make the lava. The best way to get the measurements right is to take a big glass container and pour 250ml of water into it. Mark this level with a permanent marker. Empty it out. Now pour in 166ml of water and mark that level. Now you have the level for the wax (166ml) and the rest will be the perc (83ml).

Melt the wax on a very low heat in a can (the can should be heated in a pot with water in it). Watch it all the time. When it is completely liquid, pour 166ml into the glass ­container. Now carefully pour in the perc up to the 250ml mark. Swirl the container carefully to mix it.

To function optimally, the lava lamp needs a spring at the bottom of the bottle to break the surface tension of the lava when it reaches the bottom of the lamp. You can make one by winding some steel wire around something about the thickness of a pencil. Slide the spring into the bottle.

Heat the bottle under hot water (to prevent the lava ­sticking to the sides) and slowly decant some of the liquid lava into the bottle (you can reheat the lava the same way as the wax), to a level of about 6cm. At this point add some candle dye to the lava and swirl to mix it.

Screw on the top and let the lava solidify completely. Once it’s solid, fill it up with water, leaving only the neck of the bottle empty for expansion. Now add about two teaspoons of salt. The salt raises the water’s boiling point allowing the wax to melt better, and makes the water less dense.

Now screw on the top and put it on the base. Switch it on and allow it to heat up. Give it at least three hours to get hot. If the lava won’t rise add a small amount of salt until it does. If it rises and sits at the top, let it cool; empty out the water. Fill it with water, adding less salt than before.

If the lava won’t mingle or mix when it reaches the top, add a tiny amount (about a pin head full) of dishwashing ­liquid. This just breaks the surface tension of the lava and makes it flow better. The Lava Lamp is actually a cunning piece of thermodynamics. When the Lava is cold, it is denser than the surrounding water. When it is heated it becomes a liquid, at virtually the same temperature as the surrounding water. It is at this point that it becomes less dense than the water and rises. When it reaches the top of the lamp, it cools slightly and becomes denser and sinks to the bottom, where it is heated again.