Write an article based on this "Fill a large mixing bowl with warm water and ½ cup (120 ml) of vinegar. Place them in the bowl. Soak them for 30 minutes. Remove and place them on a sheet of newspaper."
Use distilled white vinegar. Mix the ingredients together until they are well-combined.  Alternatively, you can plug up your sink and fill it with the water-vinegar solution. Depending on how much water you use, you may need to use more vinegar like 1 cup (240 ml). Make sure the pine cones are totally submerged. If they are not, then fill your bowl with more water until they are. At the halfway mark (15 minutes), use a spoon to stir the pine cones. This will help loosen and remove debris and bugs. It is normal for the pine cones to close up while they are soaking. As you are placing the pine cones on the newspaper, shake them to remove any excess water. Alternatively, you can place them in a strainer to remove excess water before placing them on the newspaper.