Choose a large, flat work area and lay newspaper on it to avoid any damage to your furniture or belongings.
Place an empty plastic water or soda bottle into a shallow box that is large enough to hold your volcano. Cover the opening of the bottle with a piece of aluminum foil so nothing gets in while you are constructing the volcano.
Crumple up newspaper and put it around the base of the bottle. This helps form the hill shape on which you will lay the paper mache.
Mix water into a bowl of wallpaper paste until the paste has the consistency of thick pudding. Tear off a strip of newspaper that is about 1 inch wide and dip it into the paste, pulling it through your fingers to evenly distribute the paste.
Place the strip of newspaper over the crumpled-up newspaper at the base of the bottle and the bottle itself. Repeat this dipping and pasting process with each strip of newspaper until the entire hill and bottle is covered up to the top. Try to form a mountain or volcano shape while you are working.
Let the paper mache volcano dry completely. Paint the volcano with brown or gray acrylic paint. Let this paint dry as well.
Remove the foil from the top of the volcano. Pour 1 tbsp. of baking soda into the top opening.
Pour 1 cup of vinegar into a measuring cup and add a few drops of red food coloring. Mix the vinegar and food coloring together.
Place a funnel into the bottle opening and pour in the vinegar mixture. Remove the funnel quickly and be prepared for the volcano to erupt immediately.