Rubber Chicken Bones What is so special about vinegar that it can make a hard bone squishy? Vinegar is considered a mild acid, but it is strong enough to dissolve away the calcium in the bone. Once the calcium is dissolved, there is nothing to keep the bone hard - all that is left is the soft bone tissue. Now you know why your mom is always trying to get you to drink milk - the calcium in milk goes to our bones to make our bones stronger. With some effort and you can really get the bone to bend.