Witch & spirit bottles, forms of "bottled spells", date back hundreds of years. These bottles are filled with items to lure-in, trap, neutralize, & even kill evil. These bottles are actively working ~ as long as the bottle & any seals remain unbroken.
These bottles are as varied as those who make them ~ & as varied as entities they are designed to capture. Historically, common contents of the bottles include nails, pins, & needles; wine or mead; hair, blood, & clippings; herbs; and ingredients representing classical elements of Fire, Water, Earth, & Air.
The main difference between witch bottles & spirit bottles is the contents, e.g. a witch bottle may not have captured anything yet, while a spirit bottle contains a spirit or evil entity.
Identification of these bottles, i.e. whether or not there are spirits or evil trapped inside, is most readily ascertained by the novice via a label naming the evil within. Spirit bottles will be tagged or labeled while witch bottles have no entities within to name. However, spirit bottle labels may be lost over the years, leaving some to think the bottles are safe to open ~ do not open them! Even should they be void of evil, the spells & castings will be set free. At best, this renders the witch bottles useless; at worst... we shudder to think.
Typically witch bottles are hidden within the structure of a building, such as buried beneath the fireplace, under the floor, or plastered inside walls. Other options, including those more suitable for renters, include burying them at the farthest northern corner of the property or placing them in an inconspicuous spot in the house. Many witches will place these bottles in their apothecaries believing this will most readily attract & catch spirits as well as allowing the witch to make sure the bottles & seals remain intact. However, witch & spirit bottles do not belong on an alter.