Use your paper plate as a base and create a mountain shaped mound. Use your thumb or finger to make a hole at least 2 inches deep and 1 inch in diameter in the middle of the mound. You may need to reshape the mound around the hole after you've created it.
Let it air dry completely and paint the entire surface with glaze to make it water resistant. This may require several coats of glaze. It's important that the hole be completely glazed so that the fake lava is not absorbed by the clay.
Fill the hole half full with vinegar and put 3-5 drops of food coloring in it. Cut a 4x4-inch square of paper towel and put a tablespoon of baking soda in the center. Fold the paper towel around the baking soda to create a sachet.
Drop the baking soda sachet into the hole when you are ready to erupt the volcano. The paper towel will unfold and dissolve and the baking soda will react to the vinegar causing the volcano to overflow.
Clean the middle of the volcano out before performing another eruption to be sure that there is no baking soda left.