A volcano for a school science project typically comes in three parts: creating the volcano model, assembling all of the ingredients for eruption and combining the ingredients to trigger the eruption process.
Mix the salt, flour, cooking oil, brown food colouring, and water together. This combination forms the modelling clay for the volcano cone. If the mixture is too sticky to handle, add a bit more salt until it can be easily handled and moulded.
Make a base for the volcano. To do this, cover a grill pan with aluminium foil. The edges of your pan should be elevated enough (at least ½ inch) to keep liquid inside the pan after your volcano erupts.
Form the volcano. Stand the soda bottle in the middle of the grill pan, and mould clay around it to form the volcano. You can use your fingers to make ridges in the clay for the "lava" to run down. Don't block the opening of the bottle with clay.
Allow the clay volcano to dry overnight. Cracks may appear in the surface of the clay as it dries, which is a normal occurrence with homemade clay. The surface of a real volcano is never smooth; so cracks actually can help create a more realistic look for your project.
Paint the volcano. Use brown paint for the volcano's base. (It shouldn't take much coverage because you used brown food colouring in the clay.) Dip a small sea sponge in black paint, and dab it off a little on a folded paper towel. Then sponge black paint onto your volcano to add a more realistic texture and to mimic rocks. Green paint can be used to paint grass and trees at the base of the volcano. Paint red around the rim of the volcano. You can allow it to drip liberally to look like lava flowing down the volcano's sides.
Prepare the volcano for eruption. Fill the soda bottle most of the way with warm water, and add orange food colouring. Then add 5 or 6 drops of dish-washing liquid to the bottle's contents. Before the warm water cools, add baking soda to the bottle. Slowly pour the vinegar into the bottle, being careful not to let it overflow. Your volcano then will erupt.