I've had making homemade lava lamps with the girls on my to-do list for almost a year, and we finally did it this week! We had SO much fun, and this is definitely an activity that we'll do again soon. The idea came from this blog via Pinterest. To make a homemade lava lamp, you need cooking oil, water, food coloring, alka seltzer, and a bottle (we used glass Snapple bottles). First, we filled 2 bottles (1 for each girl) 3/4 full with cooking oil. Then, we added the water until the bottle was…