So, we actually don't soak pine cones in vinegar. This is an alternate way of making sure the critters don't remain in the pine cones after you bring them inside. If you use vinegar, soak them for about 20 minutes and then let them dry for 24 hours before crafting. You can use the vinegar method if you prefer, but it usually causes the pine cone to close tighter. Baking pine cones causes them to open wider, which is better for this craft.