I can’t remember what prompted this activity, but when my kids get hooked on an area of interest, we usually just run with it and learn all we can! And the current area of interest was: Volcanoes!
We researched volcanoes on the internet and checked out a stack of library books and learned a lot this way. But of course, no investigation into volcanoes would be complete without the classic volcano demonstration.
To start, I did a bit of researching on how to best make the best volcano. I read many online tutorials and picked and chose elements of each to create our own. You can make your volcano out of many different materials. Clay or salt dough, chicken wire, paper mache (our choice), or even snow!
I cut a large box to create a base to work on. I then cut the top off of a 2L plastic bottle and inverted it back into the bottle like a funnel and taped it securely. Cutting the top off and inverting it was important. It allowed a bigger “crater” for which to put in the baking soda and vinegar, eliminating the need to add the baking soda and vinegar with a funnel.
We placed the bottle in the middle of the cardboard base and used strips of cardboard to make the frame of the volcano. Using masking tape, we taped one end of the cardboard strips to the top of the bottle, and then angled them down and taped to the cardboard base. This created the shape of the volcano and made a framework to support the paper mache.
The kids helped to mix up a simple raw paper mache paste using flour and water and a bit of white glue. I didn’t measure but mixed water and white flour until it resembled pancake batter (about a 1:1 ratio). The consistency is actually up to you; both thick and thin pastes will work well. Add a bit of salt to prevent molding. I also always add a few big squeezes of white glue to the mixture to increase strength, but this is entirely optional. You can find some tips and recipes for making paper mache pastes here and here.
I had a stack of newspaper strips already cut and we got to work with the messy job of volcano building! We covered up the cardboard strips by placing the newspaper strips on them and weaving them through. To ensure proper drying, we tried not to have more than 4 layers of newspaper (although the kids did apply heavily in some spots!) To ensure that we didn’t have any gaps, we did a final layer with wider strips of paper. We put some newspaper around the top of the inverted bottle to form the crater but were careful not to block the hole at all.
Then it was time to let it dry! The kids took turns with a hairdryer, but became quickly bored with it. Ensure your volcano is fully dry and hard before painting. If you want to keep your volcano for a while, any wet layers of newspaper will allow mold to grow. This can be prevented by not having too many layers of newspaper or allowing a couple of layers to dry fully before adding more. Our volcano still had a few damp spots the following day, and was not technically ready to be painted…but we couldn’t wait! I knew that we would only be keeping the volcano for a couple of days, so we went ahead and painted it anyway.
We used tempera craft paint to paint our volcano. I gave the kids brown, grey, green, white, and black, and they mixed and applied as they wished. We mixed a few handfuls of play sand into the paint to give the volcano a rock-like texture.
The addition of a few plastic animals and trees added the finishing touches to our volcano.
Supplies needed: warm water, dish soap, baking soda, red liquid food colouring, vinegar
There were many different “recipes” available on the internet for making the volcano erupt. It is best just to experiment and find what works best for you. We used a funnel to add a few cups of very warm water to the bottle (most sources say to fill the bottle about 2/3 full). Before adding the water, we put in a couple of small drops of dish soap and stirred gently. Baking soda can be added either before or after the vinegar. We tried both and adding it before provided much better results. The amount of baking soda to add is entirely up to you. Many sites say just 2 Tbsp. We did this for our first eruption but didn’t find the result to be strong enough. We then let the kids have a spoon and they just tapped in as much as they wanted, probably closer to 6-8 Tbsp. Then it was time to add the vinegar coloured with drops of red food colouring. We had a cup of vinegar ready to add but didn’t need all of it. With extra baking soda, the reaction was fast and impressive! We started by adding the vinegar with the use of a funnel, but the reaction was so quick, it was hard to remove the funnel in time to view it properly. Luckily, I had created a larger crater by cutting off the top of the bottle and inverting it into the bottle. This eliminated the need for the funnel as we could easily pour the vinegar directly into the crater. The results were impressive!
Once the reaction was complete, we piled in more baking soda (not even caring to measure anymore) and added some more vinegar. We did it again, and again, and again! The kids loved it. Once the volcano was a bit soaked, we kept it outside and continued to use it for a few days before dismantling it. Some online tutorials for making volcanoes have a hole underneath the volcano so that the bottle can be inserted when ready to use, and then removed for cleaning later. This would perhaps allow you to keep the volcano for a longer time as it could dry properly. I was not concerned with this because making the volcano was a lot of fun and learning, and I wouldn’t mind doing this again in the future.
This activity is mostly a demonstration only. In order to further scientific learning, turn this into a true experiment, and investigate some questions. Does the temperature of the water make a difference? Try ice cold water? Very hot water? Does changing the temperature of the vinegar affect the results? Can you use other liquids in place of the vinegar? Lemon juice? Hydrogen Peroxide? Can you use other things besides baking soda? Try yeast!