A perennial favourite of middle school science fairs, an erupting model volcano is not only easy to make but never fails to attract a crowd. Changing up the traditional design by adding a cross section makes this volcano project a bit different from the usual design. By essentially building half a volcano on a Plexiglas or other transparent sheet, a cross section provides a view of the interior of the model volcano.
Purchase a sheet of plastic acrylic from your local hardware store and have it cut to size, roughly 1 foot square or larger, depending on how big your volcano will be. This will form the "window" into the volcano's cross section.
Cut the soda bottle in half lengthwise. Keep the edges straight and clean so the bottle will lay flat against the Plexiglas sheet.
Cut out the neck of the bottle to widen the opening of the volcano's "crater."
Hot glue the bottle to the Plexiglas sheet along the lengthwise cuts. Make sure the bottom of the bottle is near the bottom of the Plexiglas sheet.
Glue the bottom of the bottle and bottom edge of the Plexiglas to the plywood board.
Mix the flour, salt, vegetable oil and water in the large mixing bowl and stir by hand until all the ingredients are incorporated.
Mound up the clay around the bottle on the Plexiglas sheet, moulding it into a half volcano to obscure the bottle. Paint the clay as desired to make it resemble a dirt-and-stone volcano.
Sprinkle 1 to 2 tbsp of baking soda into the bottom of the soda bottle.
In a separate container, measure out 1 cup of white vinegar, adding a couple of drops of red food colouring as desired to create a more realistic lava effect.
Pour the vinegar into the soda bottle of your volcano and watch the reaction cause an instantaneous "eruption."
Because the model volcano will be thicker at the bottom than at the top, model a portion of the bottom and allow it to dry for a while before completing the narrower neck of the volcano. This will help the clay to dry uniformly. For a delayed eruption, try pouring the vinegar into the volcano first. Wrap the baking soda in a small piece of tissue paper and drop the packet into the volcano.
Unless you have special equipment at home for cutting acrylic plastic sheeting, do not attempt to cut Plexiglas at home. Doing so risks injury to yourself and damage to your power tools.