Glue the cardboard or foam cone flat onto the poster board with craft glue.

Make your paper-mache mixture. Mix half a cup of flour and 2 cups of cold water in a bowl. Boil 2 cups of water in a saucepan, add the flour and water mixture and allow it to heat. Add 2 tbsp. of sugar and stir well. Allow it to cool. Cut strips of newspaper and place them into a bowl. Once the paper-mache mix is cool, pour it over the strips of newspaper in the bowl.

Layer the strips of newspaper over the cone to make a paper-mache volcano. Continue until the entire cone is covered. Allow the paper-mache to dry, which may take overnight.

Paint the paper-mache volcano with brown tempera paint. You might also want to paint the bottom of your poster board. You can paint it brown, paint it green to look like grass, or paint it blue to look like a volcano in the ocean.

Cut or carve a hole out of the top 2 inches of your paper-mache volcano with a craft knife. Insert a small plastic container into the hole. If the plastic container does not fit in, keep carving out more of the volcano's top until the container settles.

Add 2 tbsp. of baking soda and 2 tbsp. of dish soap into the container. Squirt in six drops of red food coloring. Once you are ready for the explosion, add 1 oz. of vinegar and stand back as the volcano erupts.