Homemade Lava Lamp, Part 1 - Your First Try

There are many ways to make homemade lava lamps.  If you surf around the web, you can find directions that vary a great degree in complexity.  Here we give you the simplest (and cheapest) approach to making one of your own.  It's a great lesson in density, but depending on how far you take it, can also include lessons on solubility and colors.

First, find an empty 1-L or 2-L plastic bottle.  Fill the bottle between 3/4 - 4/5 of the way full with water.  Next, add a few drops of food coloring to achieve the desired color for the water layer (try not to make the color too dark or the effects can be hard to see).  Next, fill the bottle the rest of the way full with olive oil.  Finally, add about 1/2 teaspoon of table salt (for a 2-L lava lamp).  You will see quickly, and probably expect, that the oil and water do not mix.  The oil floats on top of the water, because it is less dense.  The salt will push some of the oil to the bottom, and will create some motion to your lava.  It also facilitates the formation of lava bubbles. As the salt dissolves in the water, it will allow the oil ("lava") to rise again to the top.  You can add more salt to create the effect again.  You should be able to add a lot of salt until no more dissolves in the water.  

The salt can be used to make the oil move up and down, but over the long term, you are not going to want to have add salt everytime you want to make the lava move.  As an alternative, you can slowly turn the bottle over to see some neat rivulets of lava formed along the wall of the bottle, as the oil moves back to the top of the mixture.  This can be done over and over and makes a neat effect.  Make sure that the bottle is capped securely before turning, tipping, or shaking the bottle.

This is definitely an easy and inexpensive lava lamp to create.  This is one of the demos we featured at our Texas State Fair booth - simple, but effective.  No heat lamps or electricity needed - just oil, water, food coloring, salt, and a little tipping/turning of the bottle.  Hope you enjoy.  Thank you to Erin Maxfield of U.T. Arlington for contributing this activity.  We'll present some more complicated versions of the homemade lava lamp soon.