[Sunny]

Hello,

I am trying to make a lava lamp for Physics.

I using the formula at the link : http://www.oozinggoo.com/ll-form3.html

In the 3rd paragraph, it says "I added too much, and the oil floated completely" Is that referring that there is too much oil to the 70% isopropyl alcohol or is there just not enough?

Right now I have a liquid, but the oil kinda sits at the top. I was thinking that I would need to add more oil to cause it to go down...but that doesn't seem to be working...

Or do I need to add more 91% alcohol?

[Yggdrasil]

As things currently are for your setup, no matter how much oil you add, you won't get the oil to sink.  From what I can tell from the article, the way that you control how much the oil floats is by changing the composition of the water/isopropyl alcohol mixture.  Water (density ~1g/mL at room temp) is more dense than isopropyl alcohol (density ~ 0.8g/mL at room temp).  Increasing the water content of the alcohol will increase the density of the alcohol mixture and make the oil float more.  Decreasing the water content of the alcohol (e.g. by adding a more concentrated solution of alcohol) will decrease the density of the alcohol mixture and make the oil sink more.

That said, I would definitely heed the warning at the bottom of the webpage you linked to.  Heating a sealed bottle is a great way to cause an explosion.