Try other kinds of jars. Leaves, humus from a forest floor, garden soil, dead plants, green plants, peat, vegetables. Do not place your jars where infants can reach them. Discard dangerous jars carefully. This experiment carries very limited risk of infection or injury unless you fall out of a tree collecting wood or step on a rusty nail in the horse stable.
Horse manure is reputed to contain tetanus spores.
Therefore be very careful not to step on rusty nails or pitchforks in horse barns. Wear protective shoes. You must go to a doctor immediately if you suffer such an injury. Anyone likely to get such wounds should make sure his tetanus shots are up to date. If you suffer a puncture wound of the above type, it is extremely urgent that you see a doctor right away because lockjaw is extremely serious.