Beginning in the mid 1800's, poisonous substances came onto the market to control plants and vermin, and as surface cleaners. To prevent mishaps, poison bottles were given distinctive features, which today make them fun to collect. Colors like cobalt blue, inky black, and dark green ensured they were easily recognizable. So did raised lettering or inlays of the words 'POISON' or 'DEATH' (especially useful if you were fumbling by candlelight). Patterns included latticework, deep grooves, geometric shapes, and most commonly, the skull and crossbones. Look for figural bottles (including a rare few shaped like coffins or skulls) and other shapes (e.g. cigar-shaped bottles).