For this iteration you build a controlled feed. The results are dramatic and realistic and are sure to drive your geeklings wild. You’ll need:
Sandbox with enough sand to make a big mountain.
Silicone tubing (3/8")
Air source such as a bicycle pump or "bellows" style foot pump
Plastic bottle or jar with plastic lid
Generous amount of bicarbonate of soda
Vinegar/Lemon juice or some combination thereof
My crude diagram gives you the idea of the feed of this set-up. We used a 6 oz. baby bottle with a lid and a bellows foot pump with tapered end. The tubing is connected to your air source and fed through one of two 1/4" holes drilled through the lid. Feed the other tube all the way to the bottom of the bottle and bury the other end in the sand up to your crater.
Fill your crater with baking soda. Fill the bottle with vinegar/lemon juice. Make sure the lid is screwed tight and countdown…. A good pump should force the entire contents of the 6 oz. bottle into the volcano. Some plastic dinosaurs only adds to authenticity.
For an even better lesson in volcanism, you only need some water. Bury the crater and pump some water into the volcano and you get a realistic effect as the water explodes out the top or the side – just like a real reawakened volcano!